Changelog

Unreleased

Optimize the generated code for private methods

Previously when lowering private methods for old browsers, esbuild would generate one WeakSet for each private method. This mirrors similar logic for generating one WeakSet for each private field. Using a separate WeakMap for private fields is necessary as their assignment can be observable:

let it
class Bar {
  constructor() {
    it = this
  }
}
class Foo extends Bar {
  #x = 1
  #y = null.foo
  static check() {
    console.log(#x in it, #y in it)
  }
}
try { new Foo } catch {}
Foo.check()

This prints true false because this partially-initialized instance has #x but not #y. In other words, it's not true that all class instances will always have all of their private fields. However, the assignment of private methods to a class instance is not observable. In other words, it's true that all class instances will always have all of their private methods. This means esbuild can lower private methods into code where all methods share a single WeakSet, which is smaller, faster, and uses less memory. Other JavaScript processing tools such as the TypeScript compiler already make this optimization. Here's what this change looks like:

// Original code
class Foo {
  #x() { return this.#x() }
  #y() { return this.#y() }
  #z() { return this.#z() }
}

// Old output (--supported:class-private-method=false)
var _x, x_fn, _y, y_fn, _z, z_fn;
class Foo {
  constructor() {
    __privateAdd(this, _x);
    __privateAdd(this, _y);
    __privateAdd(this, _z);
  }
}
_x = new WeakSet();
x_fn = function() {
  return __privateMethod(this, _x, x_fn).call(this);
};
_y = new WeakSet();
y_fn = function() {
  return __privateMethod(this, _y, y_fn).call(this);
};
_z = new WeakSet();
z_fn = function() {
  return __privateMethod(this, _z, z_fn).call(this);
};

// New output (--supported:class-private-method=false)
var _Foo_instances, x_fn, y_fn, z_fn;
class Foo {
  constructor() {
    __privateAdd(this, _Foo_instances);
  }
}
_Foo_instances = new WeakSet();
x_fn = function() {
  return __privateMethod(this, _Foo_instances, x_fn).call(this);
};
y_fn = function() {
  return __privateMethod(this, _Foo_instances, y_fn).call(this);
};
z_fn = function() {
  return __privateMethod(this, _Foo_instances, z_fn).call(this);
};

0.20.2

Support TypeScript experimental decorators on abstract class fields (#3684)

With this release, you can now use TypeScript experimental decorators on abstract class fields. This was silently compiled incorrectly in esbuild 0.19.7 and below, and was an error from esbuild 0.19.8 to esbuild 0.20.1. Code such as the following should now work correctly:

// Original code
const log = (x: any, y: string) => console.log(y)
abstract class Foo { @log abstract foo: string }
new class extends Foo { foo = '' }

// Old output (with --loader=ts --tsconfig-raw={\"compilerOptions\":{\"experimentalDecorators\":true}})
const log = (x, y) => console.log(y);
class Foo {
}
new class extends Foo {
  foo = "";
}();

// New output (with --loader=ts --tsconfig-raw={\"compilerOptions\":{\"experimentalDecorators\":true}})
const log = (x, y) => console.log(y);
class Foo {
}
__decorateClass([
  log
], Foo.prototype, "foo", 2);
new class extends Foo {
  foo = "";
}();

JSON loader now preserves __proto__ properties (#3700)

Copying JSON source code into a JavaScript file will change its meaning if a JSON object contains the __proto__ key. A literal __proto__ property in a JavaScript object literal sets the prototype of the object instead of adding a property named __proto__, while a literal __proto__ property in a JSON object literal just adds a property named __proto__. With this release, esbuild will now work around this problem by converting JSON to JavaScript with a computed property key in this case:

// Original code
import data from 'data:application/json,{"__proto__":{"fail":true}}'
if (Object.getPrototypeOf(data)?.fail) throw 'fail'

// Old output (with --bundle)
(() => {
  // <data:application/json,{"__proto__":{"fail":true}}>
  var json_proto_fail_true_default = { __proto__: { fail: true } };

  // entry.js
  if (Object.getPrototypeOf(json_proto_fail_true_default)?.fail)
    throw "fail";
})();

// New output (with --bundle)
(() => {
  // <data:application/json,{"__proto__":{"fail":true}}>
  var json_proto_fail_true_default = { ["__proto__"]: { fail: true } };

  // example.mjs
  if (Object.getPrototypeOf(json_proto_fail_true_default)?.fail)
    throw "fail";
})();

Improve dead code removal of switch statements (#3659)

With this release, esbuild will now remove switch statements in branches when minifying if they are known to never be evaluated:

// Original code
if (true) foo(); else switch (bar) { case 1: baz(); break }

// Old output (with --minify)
if(1)foo();else switch(bar){case 1:}

// New output (with --minify)
foo();

Empty enums should behave like an object literal (#3657)

TypeScript allows you to create an empty enum and add properties to it at run time. While people usually use an empty object literal for this instead of a TypeScript enum, esbuild's enum transform didn't anticipate this use case and generated undefined instead of {} for an empty enum. With this release, you can now use an empty enum to generate an empty object literal.
```
// Original code
enum Foo {}

// Old output (with --loader=ts)
var Foo = /* @__PURE__ */ ((Foo2) => {
})(Foo || {});

// New output (with --loader=ts)
var Foo = /* @__PURE__ */ ((Foo2) => {
  return Foo2;
})(Foo || {});
```
Handle Yarn Plug'n'Play edge case with tsconfig.json (#3698)

Previously a tsconfig.json file that extends another file in a package with an exports map failed to work when Yarn's Plug'n'Play resolution was active. This edge case should work now starting with this release.
Work around issues with Deno 1.31+ (#3682)

Version 0.20.0 of esbuild changed how the esbuild child process is run in esbuild's API for Deno. Previously it used Deno.run but that API is being removed in favor of Deno.Command. As part of this change, esbuild is now calling the new unref function on esbuild's long-lived child process, which is supposed to allow Deno to exit when your code has finished running even though the child process is still around (previously you had to explicitly call esbuild's stop() function to terminate the child process for Deno to be able to exit).

However, this introduced a problem for Deno's testing API which now fails some tests that use esbuild with error: Promise resolution is still pending but the event loop has already resolved. It's unclear to me why this is happening. The call to unref was recommended by someone on the Deno core team, and calling Node's equivalent unref API has been working fine for esbuild in Node for a long time. It could be that I'm using it incorrectly, or that there's some reference counting and/or garbage collection bug in Deno's internals, or that Deno's unref just works differently than Node's unref. In any case, it's not good for Deno tests that use esbuild to be failing.

In this release, I am removing the call to unref to fix this issue. This means that you will now have to call esbuild's stop() function to allow Deno to exit, just like you did before esbuild version 0.20.0 when this regression was introduced.

Note: This regression wasn't caught earlier because Deno doesn't seem to fail tests that have outstanding setTimeout calls, which esbuild's test harness was using to enforce a maximum test runtime. Adding a setTimeout was allowing esbuild's Deno tests to succeed. So this regression doesn't necessarily apply to all people using tests in Deno.

0.20.1

Fix a bug with the CSS nesting transform (#3648)

This release fixes a bug with the CSS nesting transform for older browsers where the generated CSS could be incorrect if a selector list contained a pseudo element followed by another selector. The bug was caused by incorrectly mutating the parent rule's selector list when filtering out pseudo elements for the child rules:
```
/* Original code */
.foo {
  &:after,
  & .bar {
    color: red;
  }
}

/* Old output (with --supported:nesting=false) */
.foo .bar,
.foo .bar {
  color: red;
}

/* New output (with --supported:nesting=false) */
.foo:after,
.foo .bar {
  color: red;
}
```
Constant folding for JavaScript inequality operators (#3645)

This release introduces constant folding for the < > <= >= operators. The minifier will now replace these operators with true or false when both sides are compile-time numeric or string constants:
```
// Original code
console.log(1 < 2, '🍕' > '🧀')

// Old output (with --minify)
console.log(1<2,"🍕">"🧀");

// New output (with --minify)
console.log(!0,!1);
```

Better handling of __proto__ edge cases (#3651)

JavaScript object literal syntax contains a special case where a non-computed property with a key of __proto__ sets the prototype of the object. This does not apply to computed properties or to properties that use the shorthand property syntax introduced in ES6. Previously esbuild didn't correctly preserve the "sets the prototype" status of properties inside an object literal, meaning a property that sets the prototype could accidentally be transformed into one that doesn't and vice versa. This has now been fixed:

// Original code
function foo(__proto__) {
  return { __proto__: __proto__ } // Note: sets the prototype
}
function bar(__proto__, proto) {
  {
    let __proto__ = proto
    return { __proto__ } // Note: doesn't set the prototype
  }
}

// Old output
function foo(__proto__) {
  return { __proto__ }; // Note: no longer sets the prototype (WRONG)
}
function bar(__proto__, proto) {
  {
    let __proto__2 = proto;
    return { __proto__: __proto__2 }; // Note: now sets the prototype (WRONG)
  }
}

// New output
function foo(__proto__) {
  return { __proto__: __proto__ }; // Note: sets the prototype (correct)
}
function bar(__proto__, proto) {
  {
    let __proto__2 = proto;
    return { ["__proto__"]: __proto__2 }; // Note: doesn't set the prototype (correct)
  }
}

Fix cross-platform non-determinism with CSS color space transformations (#3650)

The Go compiler takes advantage of "fused multiply and add" (FMA) instructions on certain processors which do the operation x*y + z without intermediate rounding. This causes esbuild's CSS color space math to differ on different processors (currently ppc64le and s390x), which breaks esbuild's guarantee of deterministic output. To avoid this, esbuild's color space math now inserts a float64() cast around every single math operation. This tells the Go compiler not to use the FMA optimization.
Fix a crash when resolving a path from a directory that doesn't exist (#3634)

This release fixes a regression where esbuild could crash when resolving an absolute path if the source directory for the path resolution operation doesn't exist. While this situation doesn't normally come up, it could come up when running esbuild concurrently with another operation that mutates the file system as esbuild is doing a build (such as using git to switch branches). The underlying problem was a regression that was introduced in version 0.18.0.

0.20.0

This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild in your package.json file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.19.0 or ~0.19.0. See npm's documentation about semver for more information.

This time there is only one breaking change, and it only matters for people using Deno. Deno tests that use esbuild will now fail unless you make the change described below.

Work around API deprecations in Deno 1.40.x (#3609, #3611)

Deno 1.40.0 was just released and introduced run-time warnings about certain APIs that esbuild uses. With this release, esbuild will work around these run-time warnings by using newer APIs if they are present and falling back to the original APIs otherwise. This should avoid the warnings without breaking compatibility with older versions of Deno.

Unfortunately, doing this introduces a breaking change. The newer child process APIs lack a way to synchronously terminate esbuild's child process, so calling esbuild.stop() from within a Deno test is no longer sufficient to prevent Deno from failing a test that uses esbuild's API (Deno fails tests that create a child process without killing it before the test ends). To work around this, esbuild's stop() function has been changed to return a promise, and you now have to change esbuild.stop() to await esbuild.stop() in all of your Deno tests.
Reorder implicit file extensions within node_modules (#3341, #3608)

In version 0.18.0, esbuild changed the behavior of implicit file extensions within node_modules directories (i.e. in published packages) to prefer .js over .ts even when the --resolve-extensions= order prefers .ts over .js (which it does by default). However, doing that also accidentally made esbuild prefer .css over .ts, which caused problems for people that published packages containing both TypeScript and CSS in files with the same name.

With this release, esbuild will reorder TypeScript file extensions immediately after the last JavaScript file extensions in the implicit file extension order instead of putting them at the end of the order. Specifically the default implicit file extension order is .tsx,.ts,.jsx,.js,.css,.json which used to become .jsx,.js,.css,.json,.tsx,.ts in node_modules directories. With this release it will now become .jsx,.js,.tsx,.ts,.css,.json instead.

Why even rewrite the implicit file extension order at all? One reason is because the .js file is more likely to behave correctly than the .ts file. The behavior of the .ts file may depend on tsconfig.json and the tsconfig.json file may not even be published, or may use extends to refer to a base tsconfig.json file that wasn't published. People can get into this situation when they forget to add all .ts files to their .npmignore file before publishing to npm. Picking .js over .ts helps make it more likely that resulting bundle will behave correctly.

0.19.12

The "preserve" JSX mode now preserves JSX text verbatim (#3605)

The JSX specification deliberately doesn't specify how JSX text is supposed to be interpreted and there is no canonical way to interpret JSX text. Two most popular interpretations are Babel and TypeScript. Yes they are different (esbuild deliberately follows TypeScript by the way).

Previously esbuild normalized text to the TypeScript interpretation when the "preserve" JSX mode is active. However, "preserve" should arguably reproduce the original JSX text verbatim so that whatever JSX transform runs after esbuild is free to interpret it however it wants. So with this release, esbuild will now pass JSX text through unmodified:
```
// Original code
let el =
  <a href={'/'} title='&apos;&quot;'> some text
    {foo}
      more text </a>

// Old output (with --loader=jsx --jsx=preserve)
let el = <a href="/" title={`'"`}>
  {" some text"}
  {foo}
  {"more text "}
</a>;

// New output (with --loader=jsx --jsx=preserve)
let el = <a href={"/"} title='&apos;&quot;'> some text
    {foo}
      more text </a>;
```
Allow JSX elements as JSX attribute values

JSX has an obscure feature where you can use JSX elements in attribute position without surrounding them with {...}. It looks like this:
```
let el = <div data-ab=<><a/><b/></>/>;
```
I think I originally didn't implement it even though it's part of the JSX specification because it previously didn't work in TypeScript (and potentially also in Babel?). However, support for it was silently added in TypeScript 4.8 without me noticing and Babel has also since fixed their bugs regarding this feature. So I'm adding it to esbuild too now that I know it's widely supported.

Keep in mind that there is some ongoing discussion about removing this feature from JSX. I agree that the syntax seems out of place (it does away with the elegance of "JSX is basically just XML with {...} escapes" for something arguably harder to read, which doesn't seem like a good trade-off), but it's in the specification and TypeScript and Babel both implement it so I'm going to have esbuild implement it too. However, I reserve the right to remove it from esbuild if it's ever removed from the specification in the future. So use it with caution.
Fix a bug with TypeScript type parsing (#3574)

This release fixes a bug with esbuild's TypeScript parser where a conditional type containing a union type that ends with an infer type that ends with a constraint could fail to parse. This was caused by the "don't parse a conditional type" flag not getting passed through the union type parser. Here's an example of valid TypeScript code that previously failed to parse correctly:
```
type InferUnion<T> = T extends { a: infer U extends number } | infer U extends number ? U : never
```

0.19.11

Fix TypeScript-specific class transform edge case (#3559)

The previous release introduced an optimization that avoided transforming super() in the class constructor for TypeScript code compiled with useDefineForClassFields set to false if all class instance fields have no initializers. The rationale was that in this case, all class instance fields are omitted in the output so no changes to the constructor are needed. However, if all of this is the case and there are #private instance fields with initializers, those private instance field initializers were still being moved into the constructor. This was problematic because they were being inserted before the call to super() (since super() is now no longer transformed in that case). This release introduces an additional optimization that avoids moving the private instance field initializers into the constructor in this edge case, which generates smaller code, matches the TypeScript compiler's output more closely, and avoids this bug:
```
// Original code
class Foo extends Bar {
  #private = 1;
  public: any;
  constructor() {
    super();
  }
}

// Old output (with esbuild v0.19.9)
class Foo extends Bar {
  constructor() {
    super();
    this.#private = 1;
  }
  #private;
}

// Old output (with esbuild v0.19.10)
class Foo extends Bar {
  constructor() {
    this.#private = 1;
    super();
  }
  #private;
}

// New output
class Foo extends Bar {
  #private = 1;
  constructor() {
    super();
  }
}
```

Minifier: allow reording a primitive past a side-effect (#3568)

The minifier previously allowed reordering a side-effect past a primitive, but didn't handle the case of reordering a primitive past a side-effect. This additional case is now handled:

// Original code
function f() {
  let x = false;
  let y = x;
  const boolean = y;
  let frag = $.template(`<p contenteditable="${boolean}">hello world</p>`);
  return frag;
}

// Old output (with --minify)
function f(){const e=!1;return $.template(`<p contenteditable="${e}">hello world</p>`)}

// New output (with --minify)
function f(){return $.template('<p contenteditable="false">hello world</p>')}

Minifier: consider properties named using known Symbol instances to be side-effect free (#3561)

Many things in JavaScript can have side effects including property accesses and ToString operations, so using a symbol such as Symbol.iterator as a computed property name is not obviously side-effect free. This release adds a special case for known Symbol instances so that they are considered side-effect free when used as property names. For example, this class declaration will now be considered side-effect free:
```
class Foo {
  *[Symbol.iterator]() {
  }
}
```
Provide the stop() API in node to exit esbuild's child process (#3558)

You can now call stop() in esbuild's node API to exit esbuild's child process to reclaim the resources used. It only makes sense to do this for a long-lived node process when you know you will no longer be making any more esbuild API calls. It is not necessary to call this to allow node to exit, and it's advantageous to not call this in between calls to esbuild's API as sharing a single long-lived esbuild child process is more efficient than re-creating a new esbuild child process for every API call. This API call used to exist but was removed in version 0.9.0. This release adds it back due to a user request.

0.19.10

Fix glob imports in TypeScript files (#3319)

This release fixes a problem where bundling a TypeScript file containing a glob import could emit a call to a helper function that doesn't exist. The problem happened because esbuild's TypeScript transformation removes unused imports (which is required for correctness, as they may be type-only imports) and esbuild's glob import transformation wasn't correctly marking the imported helper function as used. This wasn't caught earlier because most of esbuild's glob import tests were written in JavaScript, not in TypeScript.
Fix require() glob imports with bundling disabled (#3546)

Previously require() calls containing glob imports were incorrectly transformed when bundling was disabled. All glob imports should only be transformed when bundling is enabled. This bug has been fixed.

Fix a panic when transforming optional chaining with define (#3551, #3554)

This release fixes a case where esbuild could crash with a panic, which was triggered by using define to replace an expression containing an optional chain. Here is an example:

// Original code
console.log(process?.env.SHELL)

// Old output (with --define:process.env={})
/* panic: Internal error (while parsing "<stdin>") */

// New output (with --define:process.env={})
var define_process_env_default = {};
console.log(define_process_env_default.SHELL);

This fix was contributed by @hi-ogawa.

Work around a bug in node's CommonJS export name detector (#3544)

The export names of a CommonJS module are dynamically-determined at run time because CommonJS exports are properties on a mutable object. But the export names of an ES module are statically-determined at module instantiation time by using import and export syntax and cannot be changed at run time.

When you import a CommonJS module into an ES module in node, node scans over the source code to attempt to detect the set of export names that the CommonJS module will end up using. That statically-determined set of names is used as the set of names that the ES module is allowed to import at module instantiation time. However, this scan appears to have bugs (or at least, can cause false positives) because it doesn't appear to do any scope analysis. Node will incorrectly consider the module to export something even if the assignment is done to a local variable instead of to the module-level exports object. For example:
```
// confuseNode.js
exports.confuseNode = function(exports) {
  // If this local is called "exports", node incorrectly
  // thinks this file has an export called "notAnExport".
  exports.notAnExport = function() {
  };
};
```
You can see that node incorrectly thinks the file confuseNode.js has an export called notAnExport when that file is loaded in an ES module context:
```
$ node -e 'import("./confuseNode.js").then(console.log)'
[Module: null prototype] {
  confuseNode: [Function (anonymous)],
  default: { confuseNode: [Function (anonymous)] },
  notAnExport: undefined
}
```
To avoid this, esbuild will now rename local variables that use the names exports and module when generating CommonJS output for the node platform.

Fix the return value of esbuild's super() shim (#3538)

Some people write constructor methods that use the return value of super() instead of using this. This isn't too common because TypeScript doesn't let you do that but it can come up when writing JavaScript. Previously esbuild's class lowering transform incorrectly transformed the return value of super() into undefined. With this release, the return value of super() will now be this instead:

// Original code
class Foo extends Object {
  field
  constructor() {
    console.log(typeof super())
  }
}
new Foo

// Old output (with --target=es6)
class Foo extends Object {
  constructor() {
    var __super = (...args) => {
      super(...args);
      __publicField(this, "field");
    };
    console.log(typeof __super());
  }
}
new Foo();

// New output (with --target=es6)
class Foo extends Object {
  constructor() {
    var __super = (...args) => {
      super(...args);
      __publicField(this, "field");
      return this;
    };
    console.log(typeof __super());
  }
}
new Foo();

Terminate the Go GC when esbuild's stop() API is called (#3552)

If you use esbuild with WebAssembly and pass the worker: false flag to esbuild.initialize(), then esbuild will run the WebAssembly module on the main thread. If you do this within a Deno test and that test calls esbuild.stop() to clean up esbuild's resources, Deno may complain that a setTimeout() call lasted past the end of the test. This happens when the Go is in the middle of a garbage collection pass and has scheduled additional ongoing garbage collection work. Normally calling esbuild.stop() will terminate the web worker that the WebAssembly module runs in, which will terminate the Go GC, but that doesn't happen if you disable the web worker with worker: false.

With this release, esbuild will now attempt to terminate the Go GC in this edge case by calling clearTimeout() on these pending timeouts.
Apply /* @__NO_SIDE_EFFECTS__ */ on tagged template literals (#3511)

Tagged template literals that reference functions annotated with a @__NO_SIDE_EFFECTS__ comment are now able to be removed via tree-shaking if the result is unused. This is a convention from Rollup. Here is an example:
```
// Original code
const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b })
html`<a>remove</a>`
x = html`<b>keep</b>`

// Old output (with --tree-shaking=true)
const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b });
html`<a>remove</a>`;
x = html`<b>keep</b>`;

// New output (with --tree-shaking=true)
const html = /* @__NO_SIDE_EFFECTS__ */ (a, ...b) => ({ a, b });
x = html`<b>keep</b>`;
```
Note that this feature currently only works within a single file, so it's not especially useful. This feature does not yet work across separate files. I still recommend using @__PURE__ annotations instead of this feature, as they have wider tooling support. The drawback of course is that @__PURE__ annotations need to be added at each call site, not at the declaration, and for non-call expressions such as template literals you need to wrap the expression in an IIFE (immediately-invoked function expression) to create a call expression to apply the @__PURE__ annotation to.
Publish builds for IBM AIX PowerPC 64-bit (#3549)

This release publishes a binary executable to npm for IBM AIX PowerPC 64-bit, which means that in theory esbuild can now be installed in that environment with npm install esbuild. This hasn't actually been tested yet. If you have access to such a system, it would be helpful to confirm whether or not doing this actually works.

0.19.9

Add support for transforming new CSS gradient syntax for older browsers

The specification called CSS Images Module Level 4 introduces new CSS gradient syntax for customizing how the browser interpolates colors in between color stops. You can now control the color space that the interpolation happens in as well as (for "polar" color spaces) control whether hue angle interpolation happens clockwise or counterclockwise. You can read more about this in Mozilla's blog post about new CSS gradient features.

With this release, esbuild will now automatically transform this syntax for older browsers in the target list. For example, here's a gradient that should appear as a rainbow in a browser that supports this new syntax:
```
/* Original code */
.rainbow-gradient {
  width: 100px;
  height: 100px;
  background: linear-gradient(in hsl longer hue, #7ff, #77f);
}

/* New output (with --target=chrome99) */
.rainbow-gradient {
  width: 100px;
  height: 100px;
  background:
    linear-gradient(
      #77ffff,
      #77ffaa 12.5%,
      #77ff80 18.75%,
      #84ff77 21.88%,
      #99ff77 25%,
      #eeff77 37.5%,
      #fffb77 40.62%,
      #ffe577 43.75%,
      #ffbb77 50%,
      #ff9077 56.25%,
      #ff7b77 59.38%,
      #ff7788 62.5%,
      #ff77dd 75%,
      #ff77f2 78.12%,
      #f777ff 81.25%,
      #cc77ff 87.5%,
      #7777ff);
}
```
You can now use this syntax in your CSS source code and esbuild will automatically convert it to an equivalent gradient for older browsers. In addition, esbuild will now also transform "double position" and "transition hint" syntax for older browsers as appropriate:
```
/* Original code */
.stripes {
  width: 100px;
  height: 100px;
  background: linear-gradient(#e65 33%, #ff2 33% 67%, #99e 67%);
}
.glow {
  width: 100px;
  height: 100px;
  background: radial-gradient(white 10%, 20%, black);
}

/* New output (with --target=chrome33) */
.stripes {
  width: 100px;
  height: 100px;
  background:
    linear-gradient(
      #e65 33%,
      #ff2 33%,
      #ff2 67%,
      #99e 67%);
}
.glow {
  width: 100px;
  height: 100px;
  background:
    radial-gradient(
      #ffffff 10%,
      #aaaaaa 12.81%,
      #959595 15.62%,
      #7b7b7b 21.25%,
      #5a5a5a 32.5%,
      #444444 43.75%,
      #323232 55%,
      #161616 77.5%,
      #000000);
}
```
You can see visual examples of these new syntax features by looking at esbuild's gradient transformation tests.

If necessary, esbuild will construct a new gradient that approximates the original gradient by recursively splitting the interval in between color stops until the approximation error is within a small threshold. That is why the above output CSS contains many more color stops than the input CSS.

Note that esbuild deliberately replaces the original gradient with the approximation instead of inserting the approximation before the original gradient as a fallback. The latest version of Firefox has multiple gradient rendering bugs (including incorrect interpolation of partially-transparent colors and interpolating non-sRGB colors using the incorrect color space). If esbuild didn't replace the original gradient, then Firefox would use the original gradient instead of the fallback the appearance would be incorrect in Firefox. In other words, the latest version of Firefox supports modern gradient syntax but interprets it incorrectly.
Add support for color(), lab(), lch(), oklab(), oklch(), and hwb() in CSS

CSS has recently added lots of new ways of specifying colors. You can read more about this in Chrome's blog post about CSS color spaces.

This release adds support for minifying colors that use the color(), lab(), lch(), oklab(), oklch(), or hwb() syntax and/or transforming these colors for browsers that don't support it yet:
```
/* Original code */
div {
  color: hwb(90deg 20% 40%);
  background: color(display-p3 1 0 0);
}

/* New output (with --target=chrome99) */
div {
  color: #669933;
  background: #ff0f0e;
  background: color(display-p3 1 0 0);
}
```
As you can see, colors outside of the sRGB color space such as color(display-p3 1 0 0) are mapped back into the sRGB gamut and inserted as a fallback for browsers that don't support the new color syntax.
Allow empty type parameter lists in certain cases (#3512)

TypeScript allows interface declarations and type aliases to have empty type parameter lists. Previously esbuild didn't handle this edge case but with this release, esbuild will now parse this syntax:
```
interface Foo<> {}
type Bar<> = {}
```
This fix was contributed by @magic-akari.

0.19.8

Add a treemap chart to esbuild's bundle analyzer (#2848)

The bundler analyzer on esbuild's website (https://esbuild.github.io/analyze/) now has a treemap chart type in addition to the two existing chart types (sunburst and flame). This should be more familiar for people coming from other similar tools, as well as make better use of large screens.
Allow decorators after the export keyword (#104)

Previously esbuild's decorator parser followed the original behavior of TypeScript's experimental decorators feature, which only allowed decorators to come before the export keyword. However, the upcoming JavaScript decorators feature also allows decorators to come after the export keyword. And with TypeScript 5.0, TypeScript now also allows experimental decorators to come after the export keyword too. So esbuild now allows this as well:
```
// This old syntax has always been permitted:
@decorator export class Foo {}
@decorator export default class Foo {}

// This new syntax is now permitted too:
export @decorator class Foo {}
export default @decorator class Foo {}
```
In addition, esbuild's decorator parser has been rewritten to fix several subtle and likely unimportant edge cases with esbuild's parsing of exports and decorators in TypeScript (e.g. TypeScript apparently does automatic semicolon insertion after interface and export interface but not after export default interface).
Pretty-print decorators using the same whitespace as the original

When printing code containing decorators, esbuild will now try to respect whether the original code contained newlines after the decorator or not. This can make generated code containing many decorators much more compact to read:
```
// Original code
class Foo {
  @a @b @c abc
  @x @y @z xyz
}

// Old output
class Foo {
  @a
  @b
  @c
  abc;
  @x
  @y
  @z
  xyz;
}

// New output
class Foo {
  @a @b @c abc;
  @x @y @z xyz;
}
```

0.19.7

Add support for bundling code that uses import attributes (#3384)

JavaScript is gaining new syntax for associating a map of string key-value pairs with individual ESM imports. The proposal is still a work in progress and is still undergoing significant changes before being finalized. However, the first iteration has already been shipping in Chromium-based browsers for a while, and the second iteration has landed in V8 and is now shipping in node, so it makes sense for esbuild to support it. Here are the two major iterations of this proposal (so far):
1. Import assertions (deprecated, will not be standardized)
  - Uses the assert keyword
  - Does not affect module resolution
  - Causes an error if the assertion fails
  - Shipping in Chrome 91+ (and in esbuild 0.11.22+)
2. Import attributes (currently set to become standardized)
  - Uses the with keyword
  - Affects module resolution
  - Unknown attributes cause an error
  - Shipping in node 21+
You can already use esbuild to bundle code that uses import assertions (the first iteration). However, this feature is mostly useless for bundlers because import assertions are not allowed to affect module resolution. It's basically only useful as an annotation on external imports, which esbuild will then preserve in the output for use in a browser (which would otherwise refuse to load certain imports).

With this release, esbuild now supports bundling code that uses import attributes (the second iteration). This is much more useful for bundlers because they are allowed to affect module resolution, which means the key-value pairs can be provided to plugins. Here's an example, which uses esbuild's built-in support for the upcoming JSON module standard:
```
// On static imports
import foo from './package.json' with { type: 'json' }
console.log(foo)

// On dynamic imports
const bar = await import('./package.json', { with: { type: 'json' } })
console.log(bar)
```
One important consequence of the change in semantics between import assertions and import attributes is that two imports with identical paths but different import attributes are now considered to be different modules. This is because the import attributes are provided to the loader, which might then use those attributes during loading. For example, you could imagine an image loader that produces an image of a different size depending on the import attributes.

Import attributes are now reported in the metafile and are now provided to on-load plugins as a map in the with property. For example, here's an esbuild plugin that turns all imports with a type import attribute equal to 'cheese' into a module that exports the cheese emoji:
```
const cheesePlugin = {
  name: 'cheese',
  setup(build) {
    build.onLoad({ filter: /.*/ }, args => {
      if (args.with.type === 'cheese') return {
        contents: `export default "🧀"`,
      }
    })
  }
}

require('esbuild').build({
  bundle: true,
  write: false,
  stdin: {
    contents: `
      import foo from 'data:text/javascript,' with { type: 'cheese' }
      console.log(foo)
    `,
  },
  plugins: [cheesePlugin],
}).then(result => {
  const code = new Function(result.outputFiles[0].text)
  code()
})
```
Warning: It's possible that the second iteration of this feature may change significantly again even though it's already shipping in real JavaScript VMs (since it has already happened once before). In that case, esbuild may end up adjusting its implementation to match the eventual standard behavior. So keep in mind that by using this, you are using an unstable upcoming JavaScript feature that may undergo breaking changes in the future.
Adjust TypeScript experimental decorator behavior (#3230, #3326, #3394)

With this release, esbuild will now allow TypeScript experimental decorators to access both static class properties and #private class names. For example:
```
const check =
  <T,>(a: T, b: T): PropertyDecorator =>
    () => console.log(a === b)

async function test() {
  class Foo {
    static #foo = 1
    static bar = 1 + Foo.#foo
    @check(Foo.#foo, 1) a: any
    @check(Foo.bar, await Promise.resolve(2)) b: any
  }
}

test().then(() => console.log('pass'))
```
This will now print true true pass when compiled by esbuild. Previously esbuild evaluated TypeScript decorators outside of the class body, so it didn't allow decorators to access Foo or #foo. Now esbuild does something different, although it's hard to concisely explain exactly what esbuild is doing now (see the background section below for more information).

Note that TypeScript's experimental decorator support is currently buggy: TypeScript's compiler passes this test if only the first @check is present or if only the second @check is present, but TypeScript's compiler fails this test if both checks are present together. I haven't changed esbuild to match TypeScript's behavior exactly here because I'm waiting for TypeScript to fix these bugs instead.

Some background: TypeScript experimental decorators don't have consistent semantics regarding the context that the decorators are evaluated in. For example, TypeScript will let you use await within a decorator, which implies that the decorator runs outside the class body (since await isn't supported inside a class body), but TypeScript will also let you use #private names, which implies that the decorator runs inside the class body (since #private names are only supported inside a class body). The value of this in a decorator is also buggy (the run-time value of this changes if any decorator in the class uses a #private name but the type of this doesn't change, leading to the type checker no longer matching reality). These inconsistent semantics make it hard for esbuild to implement this feature as decorator evaluation happens in some superposition of both inside and outside the class body that is particular to the internal implementation details of the TypeScript compiler.
Forbid --keep-names when targeting old browsers (#3477)

The --keep-names setting needs to be able to assign to the name property on functions and classes. However, before ES6 this property was non-configurable, and attempting to assign to it would throw an error. So with this release, esbuild will no longer allow you to enable this setting while also targeting a really old browser.

0.19.6

Fix a constant folding bug with bigint equality

This release fixes a bug where esbuild incorrectly checked for bigint equality by checking the equality of the bigint literal text. This is correct if the bigint doesn't have a radix because bigint literals without a radix are always in canonical form (since leading zeros are not allowed). However, this is incorrect if the bigint has a radix (e.g. 0x123n) because the canonical form is not enforced when a radix is present.
```
// Original code
console.log(!!0n, !!1n, 123n === 123n)
console.log(!!0x0n, !!0x1n, 123n === 0x7Bn)

// Old output
console.log(false, true, true);
console.log(true, true, false);

// New output
console.log(false, true, true);
console.log(!!0x0n, !!0x1n, 123n === 0x7Bn);
```

Add some improvements to the JavaScript minifier

This release adds more cases to the JavaScript minifier, including support for inlining String.fromCharCode and String.prototype.charCodeAt when possible:

// Original code
document.onkeydown = e => e.keyCode === 'A'.charCodeAt(0) && console.log(String.fromCharCode(55358, 56768))

// Old output (with --minify)
document.onkeydown=o=>o.keyCode==="A".charCodeAt(0)&&console.log(String.fromCharCode(55358,56768));

// New output (with --minify)
document.onkeydown=o=>o.keyCode===65&&console.log("🧀");

In addition, immediately-invoked function expressions (IIFEs) that return a single expression are now inlined when minifying. This makes it possible to use IIFEs in combination with @__PURE__ annotations to annotate arbitrary expressions as side-effect free without the IIFE wrapper impacting code size. For example:

// Original code
const sideEffectFreeOffset = /* @__PURE__ */ (() => computeSomething())()
use(sideEffectFreeOffset)

// Old output (with --minify)
const e=(()=>computeSomething())();use(e);

// New output (with --minify)
const e=computeSomething();use(e);

Automatically prefix the mask-composite CSS property for WebKit (#3493)

The mask-composite property will now be prefixed as -webkit-mask-composite for older WebKit-based browsers. In addition to prefixing the property name, handling older browsers also requires rewriting the values since WebKit uses non-standard names for the mask composite modes:

/* Original code */
div {
  mask-composite: add, subtract, intersect, exclude;
}

/* New output (with --target=chrome100) */
div {
  -webkit-mask-composite:
    source-over,
    source-out,
    source-in,
    xor;
  mask-composite:
    add,
    subtract,
    intersect,
    exclude;
}

Avoid referencing this from JSX elements in derived class constructors (#3454)

When you enable --jsx=automatic and --jsx-dev, the JSX transform is supposed to insert this as the last argument to the jsxDEV function. I'm not sure exactly why this is and I can't find any specification for it, but in any case this causes the generated code to crash when you use a JSX element in a derived class constructor before the call to super() as this is not allowed to be accessed at that point. For example
```
// Original code
class ChildComponent extends ParentComponent {
  constructor() {
    super(<div />)
  }
}

// Problematic output (with --loader=jsx --jsx=automatic --jsx-dev)
import { jsxDEV } from "react/jsx-dev-runtime";
class ChildComponent extends ParentComponent {
  constructor() {
    super(/* @__PURE__ */ jsxDEV("div", {}, void 0, false, {
      fileName: "<stdin>",
      lineNumber: 3,
      columnNumber: 15
    }, this)); // The reference to "this" crashes here
  }
}
```
The TypeScript compiler doesn't handle this at all while the Babel compiler just omits this for the entire constructor (even after the call to super()). There seems to be no specification so I can't be sure that this change doesn't break anything important. But given that Babel is pretty loose with this and TypeScript doesn't handle this at all, I'm guessing this value isn't too important. React's blog post seems to indicate that this value was intended to be used for a React-specific migration warning at some point, so it could even be that this value is irrelevant now. Anyway the crash in this case should now be fixed.
Allow package subpath imports to map to node built-ins (#3485)

You are now able to use a subpath import in your package to resolve to a node built-in module. For example, with a package.json file like this:
```
{
  "type": "module",
  "imports": {
    "#stream": {
      "node": "stream",
      "default": "./stub.js"
    }
  }
}
```
You can now import from node's stream module like this:
```
import * as stream from '#stream';
console.log(Object.keys(stream));
```
This will import from node's stream module when the platform is node and from ./stub.js otherwise.
No longer throw an error when a Symbol is missing (#3453)

Certain JavaScript syntax features use special properties on the global Symbol object. For example, the asynchronous iteration syntax uses Symbol.asyncIterator. Previously esbuild's generated code for older browsers required this symbol to be polyfilled. However, starting with this release esbuild will use Symbol.for() to construct these symbols if they are missing instead of throwing an error about a missing polyfill. This means your code no longer needs to include a polyfill for missing symbols as long as your code also uses Symbol.for() for missing symbols.
Parse upcoming changes to TypeScript syntax (#3490, #3491)

With this release, you can now use from as the name of a default type-only import in TypeScript code, as well as of as the name of an await using loop iteration variable:
```
import type from from 'from'
for (await using of of of) ;
```
This matches similar changes in the TypeScript compiler (#56376 and #55555) which will start allowing this syntax in an upcoming version of TypeScript. Please never actually write code like this.

The type-only import syntax change was contributed by @magic-akari.

0.19.5

Fix a regression in 0.19.0 regarding paths in tsconfig.json (#3354)

The fix in esbuild version 0.19.0 to process tsconfig.json aliases before the --packages=external setting unintentionally broke an edge case in esbuild's handling of certain tsconfig.json aliases where there are multiple files with the same name in different directories. This release adjusts esbuild's behavior for this edge case so that it passes while still processing aliases before --packages=external. Please read the linked issue for more details.
Fix a CSS font property minification bug (#3452)

This release fixes a bug where esbuild's CSS minifier didn't insert a space between the font size and the font family in the font CSS shorthand property in the edge case where the original source code didn't already have a space and the leading string token was shortened to an identifier:
```
/* Original code */
.foo { font: 16px"Menlo"; }

/* Old output (with --minify) */
.foo{font:16pxMenlo}

/* New output (with --minify) */
.foo{font:16px Menlo}
```
Fix bundling CSS with asset names containing spaces (#3410)

Assets referenced via CSS url() tokens may cause esbuild to generate invalid output when bundling if the file name contains spaces (e.g. url(image 2.png)). With this release, esbuild will now quote all bundled asset references in url() tokens to avoid this problem. This only affects assets loaded using the file and copy loaders.
Fix invalid CSS url() tokens in @import rules (#3426)

In the future, CSS url() tokens may contain additional stuff after the URL. This is irrelevant today as no CSS specification does this. But esbuild previously had a bug where using these tokens in an @import rule resulted in malformed output. This bug has been fixed.
Fix browser + false + type: module in package.json (#3367)

The browser field in package.json allows you to map a file to false to have it be treated as an empty file when bundling for the browser. However, if package.json contains "type": "module" then all .js files will be considered ESM, not CommonJS. Importing a named import from an empty CommonJS file gives you undefined, but importing a named export from an empty ESM file is a build error. This release changes esbuild's interpretation of these files mapped to false in this situation from ESM to CommonJS to avoid generating build errors for named imports.
Fix a bug in top-level await error reporting (#3400)

Using require() on a file that contains top-level await is not allowed because require() must return synchronously and top-level await makes that impossible. You will get a build error if you try to bundle code that does this with esbuild. This release fixes a bug in esbuild's error reporting code for complex cases of this situation involving multiple levels of imports to get to the module containing the top-level await.
Update to Unicode 15.1.0

The character tables that determine which characters form valid JavaScript identifiers have been updated from Unicode version 15.0.0 to the newly-released Unicode version 15.1.0. I'm not putting an example in the release notes because all of the new characters will likely just show up as little squares since fonts haven't been updated yet. But you can read https://www.unicode.org/versions/Unicode15.1.0/#Summary for more information about the changes.

This upgrade was contributed by @JLHwung.

0.19.4

Fix printing of JavaScript decorators in tricky cases (#3396)

This release fixes some bugs where esbuild's pretty-printing of JavaScript decorators could incorrectly produced code with a syntax error. The problem happened because esbuild sometimes substitutes identifiers for other expressions in the pretty-printer itself, but the decision about whether to wrap the expression or not didn't account for this. Here are some examples:

// Original code
import { constant } from './constants.js'
import { imported } from 'external'
import { undef } from './empty.js'
class Foo {
  @constant()
  @imported()
  @undef()
  foo
}

// Old output (with --bundle --format=cjs --packages=external --minify-syntax)
var import_external = require("external");
var Foo = class {
  @123()
  @(0, import_external.imported)()
  @(void 0)()
  foo;
};

// New output (with --bundle --format=cjs --packages=external --minify-syntax)
var import_external = require("external");
var Foo = class {
  @(123())
  @((0, import_external.imported)())
  @((void 0)())
  foo;
};

Allow pre-release versions to be passed to target (#3388)

People want to be able to pass version numbers for unreleased versions of node (which have extra stuff after the version numbers) to esbuild's target setting and have esbuild do something reasonable with them. These version strings are of course not present in esbuild's internal feature compatibility table because an unreleased version has not been released yet (by definition). With this release, esbuild will now attempt to accept these version strings passed to target and do something reasonable with them.

0.19.3

Fix list-style-type with the local-css loader (#3325)

The local-css loader incorrectly treated all identifiers provided to list-style-type as a custom local identifier. That included identifiers such as none which have special meaning in CSS, and which should not be treated as custom local identifiers. This release fixes this bug:
```
/* Original code */
ul { list-style-type: none }

/* Old output (with --loader=local-css) */
ul {
  list-style-type: stdin_none;
}

/* New output (with --loader=local-css) */
ul {
  list-style-type: none;
}
```
Note that this bug only affected code using the local-css loader. It did not affect code using the css loader.

Avoid inserting temporary variables before use strict (#3322)

This release fixes a bug where esbuild could incorrectly insert automatically-generated temporary variables before use strict directives:

// Original code
function foo() {
  'use strict'
  a.b?.c()
}

// Old output (with --target=es6)
function foo() {
  var _a;
  "use strict";
  (_a = a.b) == null ? void 0 : _a.c();
}

// New output (with --target=es6)
function foo() {
  "use strict";
  var _a;
  (_a = a.b) == null ? void 0 : _a.c();
}

Adjust TypeScript enum output to better approximate tsc (#3329)

TypeScript enum values can be either number literals or string literals. Numbers create a bidirectional mapping between the name and the value but strings only create a unidirectional mapping from the name to the value. When the enum value is neither a number literal nor a string literal, TypeScript and esbuild both default to treating it as a number:
```
// Original TypeScript code
declare const foo: any
enum Foo {
  NUMBER = 1,
  STRING = 'a',
  OTHER = foo,
}

// Compiled JavaScript code (from "tsc")
var Foo;
(function (Foo) {
  Foo[Foo["NUMBER"] = 1] = "NUMBER";
  Foo["STRING"] = "a";
  Foo[Foo["OTHER"] = foo] = "OTHER";
})(Foo || (Foo = {}));
```
However, TypeScript does constant folding slightly differently than esbuild. For example, it may consider template literals to be string literals in some cases:
```
// Original TypeScript code
declare const foo = 'foo'
enum Foo {
  PRESENT = `${foo}`,
  MISSING = `${bar}`,
}

// Compiled JavaScript code (from "tsc")
var Foo;
(function (Foo) {
  Foo["PRESENT"] = "foo";
  Foo[Foo["MISSING"] = `${bar}`] = "MISSING";
})(Foo || (Foo = {}));
```
The template literal initializer for PRESENT is treated as a string while the template literal initializer for MISSING is treated as a number. Previously esbuild treated both of these cases as a number but starting with this release, esbuild will now treat both of these cases as a string. This doesn't exactly match the behavior of tsc but in the case where the behavior diverges tsc reports a compile error, so this seems like acceptible behavior for esbuild. Note that handling these cases completely correctly would require esbuild to parse type declarations (see the declare keyword), which esbuild deliberately doesn't do.

Ignore case in CSS in more places (#3316)

This release makes esbuild's CSS support more case-agnostic, which better matches how browsers work. For example:

/* Original code */
@KeyFrames Foo { From { OpaCity: 0 } To { OpaCity: 1 } }
body { CoLoR: YeLLoW }

/* Old output (with --minify) */
@KeyFrames Foo{From {OpaCity: 0} To {OpaCity: 1}}body{CoLoR:YeLLoW}

/* New output (with --minify) */
@KeyFrames Foo{0%{OpaCity:0}To{OpaCity:1}}body{CoLoR:#ff0}

Please never actually write code like this.

Improve the error message for null entries in exports (#3377)

Package authors can disable package export paths with the exports map in package.json. With this release, esbuild now has a clearer error message that points to the null token in package.json itself instead of to the surrounding context. Here is an example of the new error message:

✘ [ERROR] Could not resolve "msw/browser"

    lib/msw-config.ts:2:28:
      2 │ import { setupWorker } from 'msw/browser';
        ╵                             ~~~~~~~~~~~~~

  The path "./browser" cannot be imported from package "msw" because it was explicitly disabled by
  the package author here:

    node_modules/msw/package.json:17:14:
      17 │       "node": null,
         ╵               ~~~~

  You can mark the path "msw/browser" as external to exclude it from the bundle, which will remove
  this error and leave the unresolved path in the bundle.

Parse and print the with keyword in import statements

JavaScript was going to have a feature called "import assertions" that adds an assert keyword to import statements. It looked like this:
```
import stuff from './stuff.json' assert { type: 'json' }
```
The feature provided a way to assert that the imported file is of a certain type (but was not allowed to affect how the import is interpreted, even though that's how everyone expected it to behave). The feature was fully specified and then actually implemented and shipped in Chrome before the people behind the feature realized that they should allow it to affect how the import is interpreted after all. So import assertions are no longer going to be added to the language.

Instead, the current proposal is to add a feature called "import attributes" instead that adds a with keyword to import statements. It looks like this:
```
import stuff from './stuff.json' with { type: 'json' }
```
This feature provides a way to affect how the import is interpreted. With this release, esbuild now has preliminary support for parsing and printing this new with keyword. The with keyword is not yet interpreted by esbuild, however, so bundling code with it will generate a build error. All this release does is allow you to use esbuild to process code containing it (such as removing types from TypeScript code). Note that this syntax is not yet a part of JavaScript and may be removed or altered in the future if the specification changes (which it already has once, as described above). If that happens, esbuild reserves the right to remove or alter its support for this syntax too.

0.19.2

Update how CSS nesting is parsed again

CSS nesting syntax has been changed again, and esbuild has been updated to match. Type selectors may now be used with CSS nesting:
```
.foo {
  div {
    color: red;
  }
}
```
Previously this was disallowed in the CSS specification because it's ambiguous whether an identifier is a declaration or a nested rule starting with a type selector without requiring unbounded lookahead in the parser. It has now been allowed because the CSS working group has decided that requiring unbounded lookahead is acceptable after all.

Note that this change means esbuild no longer considers any existing browser to support CSS nesting since none of the existing browsers support this new syntax. CSS nesting will now always be transformed when targeting a browser. This situation will change in the future as browsers add support for this new syntax.
Fix a scope-related bug with --drop-labels= (#3311)

The recently-released --drop-labels= feature previously had a bug where esbuild's internal scope stack wasn't being restored properly when a statement with a label was dropped. This could manifest as a tree-shaking issue, although it's possible that this could have also been causing other subtle problems too. The bug has been fixed in this release.
Make renamed CSS names unique across entry points (#3295)

Previously esbuild's generated names for local names in CSS were only unique within a given entry point (or across all entry points when code splitting was enabled). That meant that building multiple entry points with esbuild could result in local names being renamed to the same identifier even when those entry points were built simultaneously within a single esbuild API call. This problem was especially likely to happen with minification enabled. With this release, esbuild will now avoid renaming local names from two separate entry points to the same name if those entry points were built with a single esbuild API call, even when code splitting is disabled.
Fix CSS ordering bug with @layer before @import

CSS lets you put @layer rules before @import rules to define the order of layers in a stylesheet. Previously esbuild's CSS bundler incorrectly ordered these after the imported files because before the introduction of cascade layers to CSS, imported files could be bundled by removing the @import rules and then joining files together in the right order. But with @layer, CSS files may now need to be split apart into multiple pieces in the bundle. For example:
```
/* Original code */
@layer start;
@import "data:text/css,@layer inner.start;";
@import "data:text/css,@layer inner.end;";
@layer end;

/* Old output (with --bundle) */
@layer inner.start;
@layer inner.end;
@layer start;
@layer end;

/* New output (with --bundle) */
@layer start;
@layer inner.start;
@layer inner.end;
@layer end;
```

Unwrap nested duplicate @media rules (#3226)

With this release, esbuild's CSS minifier will now automatically unwrap duplicate nested @media rules:

/* Original code */
@media (min-width: 1024px) {
  .foo { color: red }
  @media (min-width: 1024px) {
    .bar { color: blue }
  }
}

/* Old output (with --minify) */
@media (min-width: 1024px){.foo{color:red}@media (min-width: 1024px){.bar{color:#00f}}}

/* New output (with --minify) */
@media (min-width: 1024px){.foo{color:red}.bar{color:#00f}}

These rules are unlikely to be authored manually but may result from using frameworks such as Tailwind to generate CSS.

0.19.1

Fix a regression with baseURL in tsconfig.json (#3307)

The previous release moved tsconfig.json path resolution before --packages=external checks to allow the paths field in tsconfig.json to avoid a package being marked as external. However, that reordering accidentally broke the behavior of the baseURL field from tsconfig.json. This release moves these path resolution rules around again in an attempt to allow both of these cases to work.
Parse TypeScript type arguments for JavaScript decorators (#3308)

When parsing JavaScript decorators in TypeScript (i.e. with experimentalDecorators disabled), esbuild previously didn't parse type arguments. Type arguments will now be parsed starting with this release. For example:
```
@foo<number>
@bar<number, string>()
class Foo {}
```
Fix glob patterns matching extra stuff at the end (#3306)

Previously glob patterns such as ./*.js would incorrectly behave like ./*.js* during path matching (also matching .js.map files, for example). This was never intentional behavior, and has now been fixed.
Change the permissions of esbuild's generated output files (#3285)

This release changes the permissions of the output files that esbuild generates to align with the default behavior of node's fs.writeFileSync function. Since most tools written in JavaScript use fs.writeFileSync, this should make esbuild more consistent with how other JavaScript build tools behave.

The full Unix-y details: Unix permissions use three-digit octal notation where the three digits mean "user, group, other" in that order. Within a digit, 4 means "read" and 2 means "write" and 1 means "execute". So 6 == 4 + 2 == read + write. Previously esbuild uses 0644 permissions (the leading 0 means octal notation) but the permissions for fs.writeFileSync defaults to 0666, so esbuild will now use 0666 permissions. This does not necessarily mean that the files esbuild generates will end up having 0666 permissions, however, as there is another Unix feature called "umask" where the operating system masks out some of these bits. If your umask is set to 0022 then the generated files will have 0644 permissions, and if your umask is set to 0002 then the generated files will have 0664 permissions.
Fix a subtle CSS ordering issue with @import and @layer

With this release, esbuild may now introduce additional @layer rules when bundling CSS to better preserve the layer ordering of the input code. Here's an example of an edge case where this matters:
```
/* entry.css */
@import "a.css";
@import "b.css";
@import "a.css";
```
```
/* a.css */
@layer a {
  body {
    background: red;
  }
}
```
```
/* b.css */
@layer b {
  body {
    background: green;
  }
}
```
This CSS should set the body background to green, which is what happens in the browser. Previously esbuild generated the following output which incorrectly sets the body background to red:
```
/* b.css */
@layer b {
  body {
    background: green;
  }
}

/* a.css */
@layer a {
  body {
    background: red;
  }
}
```
This difference in behavior is because the browser evaluates a.css + b.css + a.css (in CSS, each @import is replaced with a copy of the imported file) while esbuild was only writing out b.css + a.css. The first copy of a.css wasn't being written out by esbuild for two reasons: 1) bundlers care about code size and try to avoid emitting duplicate CSS and 2) when there are multiple copies of a CSS file, normally only the last copy matters since the last declaration with equal specificity wins in CSS.

However, @layer was recently added to CSS and for @layer the first copy matters because layers are ordered using their first location in source code order. This introduction of @layer means esbuild needs to change its bundling algorithm. An easy solution would be for esbuild to write out a.css twice, but that would be inefficient. So what I'm going to try to have esbuild do with this release is to write out an abbreviated form of the first copy of a CSS file that only includes the @layer information, and then still only write out the full CSS file once for the last copy. So esbuild's output for this edge case now looks like this:
```
/* a.css */
@layer a;

/* b.css */
@layer b {
  body {
    background: green;
  }
}

/* a.css */
@layer a {
  body {
    background: red;
  }
}
```
The behavior of the bundled CSS now matches the behavior of the unbundled CSS. You may be wondering why esbuild doesn't just write out a.css first followed by b.css. That would work in this case but it doesn't work in general because for any rules outside of a @layer rule, the last copy should still win instead of the first copy.
Fix a bug with esbuild's TypeScript type definitions (#3299)

This release fixes a copy/paste error with the TypeScript type definitions for esbuild's JS API:
```
 export interface TsconfigRaw {
   compilerOptions?: {
-    baseUrl?: boolean
+    baseUrl?: string
     ...
   }
 }
```
This fix was contributed by @privatenumber.

0.19.0

This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild in your package.json file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.18.0 or ~0.18.0. See npm's documentation about semver for more information.

Handle import paths containing wildcards (#56, #700, #875, #976, #2221, #2515)

This release introduces wildcards in import paths in two places:
- Entry points
  
  You can now pass a string containing glob-style wildcards such as ./src/*.ts as an entry point and esbuild will search the file system for files that match the pattern. This can be used to easily pass esbuild all files with a certain extension on the command line in a cross-platform way. Previously you had to rely on the shell to perform glob expansion, but that is obviously shell-dependent and didn't work at all on Windows. Note that to use this feature on the command line you will have to quote the pattern so it's passed verbatim to esbuild without any expansion by the shell. Here's an example:
```
esbuild --minify "./src/*.ts" --outdir=out
```
  Specifically the * character will match any character except for the / character, and the /**/ character sequence will match a path separator followed by zero or more path elements. Other wildcard operators found in glob patterns such as ? and [...] are not supported.
- Run-time import paths
  
  Import paths that are evaluated at run-time can now be bundled in certain limited situations. The import path expression must be a form of string concatenation and must start with either ./ or ../. Each non-string expression in the string concatenation chain becomes a wildcard. The * wildcard is chosen unless the previous character is a /, in which case the /**/* character sequence is used. Some examples:
```
// These two forms are equivalent
const json1 = await import('./data/' + kind + '.json')
const json2 = await import(`./data/${kind}.json`)
```
  This feature works with require(...) and import(...) because these can all accept run-time expressions. It does not work with import and export statements because these cannot accept run-time expressions. If you want to prevent esbuild from trying to bundle these imports, you should move the string concatenation expression outside of the require(...) or import(...). For example:
```
// This will be bundled
const json1 = await import('./data/' + kind + '.json')

// This will not be bundled
const path = './data/' + kind + '.json'
const json2 = await import(path)
```
  Note that using this feature means esbuild will potentially do a lot of file system I/O to find all possible files that might match the pattern. This is by design, and is not a bug. If this is a concern, I recommend either avoiding the /**/ pattern (e.g. by not putting a / before a wildcard) or using this feature only in directory subtrees which do not have many files that don't match the pattern (e.g. making a subdirectory for your JSON files and explicitly including that subdirectory in the pattern).
Path aliases in tsconfig.json no longer count as packages (#2792, #3003, #3160, #3238)

Setting --packages=external tells esbuild to make all import paths external when they look like a package path. For example, an import of ./foo/bar is not a package path and won't be external while an import of foo/bar is a package path and will be external. However, the paths field in tsconfig.json allows you to create import paths that look like package paths but that do not resolve to packages. People do not want these paths to count as package paths. So with this release, the behavior of --packages=external has been changed to happen after the tsconfig.json path remapping step.
Use the local-css loader for .module.css files by default (#20)

With this release the css loader is still used for .css files except that .module.css files now use the local-css loader. This is a common convention in the web development community. If you need .module.css files to use the css loader instead, then you can override this behavior with --loader:.module.css=css.

0.18.20

Support advanced CSS @import rules (#953, #3137)

CSS @import statements have been extended to allow additional trailing tokens after the import path. These tokens sort of make the imported file behave as if it were wrapped in a @layer, @supports, and/or @media rule. Here are some examples:
```
@import url(foo.css);
@import url(foo.css) layer;
@import url(foo.css) layer(bar);
@import url(foo.css) layer(bar) supports(display: flex);
@import url(foo.css) layer(bar) supports(display: flex) print;
@import url(foo.css) layer(bar) print;
@import url(foo.css) supports(display: flex);
@import url(foo.css) supports(display: flex) print;
@import url(foo.css) print;
```
You can read more about this advanced syntax here. With this release, esbuild will now bundle @import rules with these trailing tokens and will wrap the imported files in the corresponding rules. Note that this now means a given imported file can potentially appear in multiple places in the bundle. However, esbuild will still only load it once (e.g. on-load plugins will only run once per file, not once per import).

0.18.19

Implement composes from CSS modules (#20)

This release implements the composes annotation from the CSS modules specification. It provides a way for class selectors to reference other class selectors (assuming you are using the local-css loader). And with the from syntax, this can even work with local names across CSS files. For example:
```
// app.js
import { submit } from './style.css'
const div = document.createElement('div')
div.className = submit
document.body.appendChild(div)
```
```
/* style.css */
.button {
  composes: pulse from "anim.css";
  display: inline-block;
}
.submit {
  composes: button;
  font-weight: bold;
}
```
```
/* anim.css */
@keyframes pulse {
  from, to { opacity: 1 }
  50% { opacity: 0.5 }
}
.pulse {
  animation: 2s ease-in-out infinite pulse;
}
```
Bundling this with esbuild using --bundle --outdir=dist --loader:.css=local-css now gives the following:
```
(() => {
  // style.css
  var submit = "anim_pulse style_button style_submit";

  // app.js
  var div = document.createElement("div");
  div.className = submit;
  document.body.appendChild(div);
})();
```
```
/* anim.css */
@keyframes anim_pulse {
  from, to {
    opacity: 1;
  }
  50% {
    opacity: 0.5;
  }
}
.anim_pulse {
  animation: 2s ease-in-out infinite anim_pulse;
}

/* style.css */
.style_button {
  display: inline-block;
}
.style_submit {
  font-weight: bold;
}
```
Import paths in the composes: ... from syntax are resolved using the new composes-from import kind, which can be intercepted by plugins during import path resolution when bundling is enabled.

Note that the order in which composed CSS classes from separate files appear in the bundled output file is deliberately undefined by design (see the specification for details). You are not supposed to declare the same CSS property in two separate class selectors and then compose them together. You are only supposed to compose CSS class selectors that declare non-overlapping CSS properties.

Issue #20 (the issue tracking CSS modules) is esbuild's most-upvoted issue! With this change, I now consider esbuild's implementation of CSS modules to be complete. There are still improvements to make and there may also be bugs with the current implementation, but these can be tracked in separate issues.
Fix non-determinism with tsconfig.json and symlinks (#3284)

This release fixes an issue that could cause esbuild to sometimes emit incorrect build output in cases where a file under the effect of tsconfig.json is inconsistently referenced through a symlink. It can happen when using npm link to create a symlink within node_modules to an unpublished package. The build result was non-deterministic because esbuild runs module resolution in parallel and the result of the tsconfig.json lookup depended on whether the import through the symlink or not through the symlink was resolved first. This problem was fixed by moving the realpath operation before the tsconfig.json lookup.
Add a hash property to output files (#3084, #3293)

As a convenience, every output file in esbuild's API now includes a hash property that is a hash of the contents field. This is the hash that's used internally by esbuild to detect changes between builds for esbuild's live-reload feature. You may also use it to detect changes between your own builds if its properties are sufficient for your use case.

This feature has been added directly to output file objects since it's just a hash of the contents field, so it makes conceptual sense to store it in the same location. Another benefit of putting it there instead of including it as a part of the watch mode API is that it can be used without watch mode enabled. You can use it to compare the output of two independent builds that were done at different times.

The hash algorithm (currently XXH64) is implementation-dependent and may be changed at any time in between esbuild versions. If you don't like esbuild's choice of hash algorithm then you are welcome to hash the contents yourself instead. As with any hash algorithm, note that while two different hashes mean that the contents are different, two equal hashes do not necessarily mean that the contents are equal. You may still want to compare the contents in addition to the hashes to detect with certainty when output files have been changed.
Avoid generating duplicate prefixed declarations in CSS (#3292)

There was a request for esbuild's CSS prefixer to avoid generating a prefixed declaration if a declaration by that name is already present in the same rule block. So with this release, esbuild will now avoid doing this:
```
/* Original code */
body {
  backdrop-filter: blur(30px);
  -webkit-backdrop-filter: blur(45px);
}

/* Old output (with --target=safari12) */
body {
  -webkit-backdrop-filter: blur(30px);
  backdrop-filter: blur(30px);
  -webkit-backdrop-filter: blur(45px);
}

/* New output (with --target=safari12) */
body {
  backdrop-filter: blur(30px);
  -webkit-backdrop-filter: blur(45px);
}
```
This can result in a visual difference in certain cases (for example if the browser understands blur(30px) but not blur(45px), it will be able to fall back to blur(30px)). But this change means esbuild now matches the behavior of Autoprefixer which is probably a good representation of how people expect this feature to work.

0.18.18

Fix asset references with the --line-limit flag (#3286)

The recently-released --line-limit flag tells esbuild to terminate long lines after they pass this length limit. This includes automatically wrapping long strings across multiple lines using escaped newline syntax. However, using this could cause esbuild to generate incorrect code for references from generated output files to assets in the bundle (i.e. files loaded with the file or copy loaders). This is because esbuild implements asset references internally using find-and-replace with a randomly-generated string, but the find operation fails if the string is split by an escaped newline due to line wrapping. This release fixes the problem by not wrapping these strings. This issue affected asset references in both JS and CSS files.

Support local names in CSS for @keyframe, @counter-style, and @container (#20)

This release extends support for local names in CSS files loaded with the local-css loader to cover the @keyframe, @counter-style, and @container rules (and also animation, list-style, and container declarations). Here's an example:

@keyframes pulse {
  from, to { opacity: 1 }
  50% { opacity: 0.5 }
}
@counter-style moon {
  system: cyclic;
  symbols: 🌕 🌖 🌗 🌘 🌑 🌒 🌓 🌔;
}
@container squish {
  li { float: left }
}
ul {
  animation: 2s ease-in-out infinite pulse;
  list-style: inside moon;
  container: squish / size;
}

With the local-css loader enabled, that CSS will be turned into something like this (with the local name mapping exposed to JS):

@keyframes stdin_pulse {
  from, to {
    opacity: 1;
  }
  50% {
    opacity: 0.5;
  }
}
@counter-style stdin_moon {
  system: cyclic;
  symbols: 🌕 🌖 🌗 🌘 🌑 🌒 🌓 🌔;
}
@container stdin_squish {
  li {
    float: left;
  }
}
ul {
  animation: 2s ease-in-out infinite stdin_pulse;
  list-style: inside stdin_moon;
  container: stdin_squish / size;
}

If you want to use a global name within a file loaded with the local-css loader, you can use a :global selector to do that:

div {
  /* All symbols are global inside this scope (i.e.
   * "pulse", "moon", and "squish" are global below) */
  :global {
    animation: 2s ease-in-out infinite pulse;
    list-style: inside moon;
    container: squish / size;
  }
}

If you want to use @keyframes, @counter-style, or @container with a global name, make sure it's in a file that uses the css or global-css loader instead of the local-css loader. For example, you can configure --loader:.module.css=local-css so that the local-css loader only applies to *.module.css files.

Support strings as keyframe animation names in CSS (#2555)

With this release, esbuild will now parse animation names that are specified as strings and will convert them to identifiers. The CSS specification allows animation names to be specified using either identifiers or strings but Chrome only understands identifiers, so esbuild will now always convert string names to identifier names for Chrome compatibility:

/* Original code */
@keyframes "hide menu" {
  from { opacity: 1 }
  to { opacity: 0 }
}
menu.hide {
  animation: 0.5s ease-in-out "hide menu";
}

/* Old output */
@keyframes "hide menu" { from { opacity: 1 } to { opacity: 0 } }
menu.hide {
  animation: 0.5s ease-in-out "hide menu";
}

/* New output */
@keyframes hide\ menu {
  from {
    opacity: 1;
  }
  to {
    opacity: 0;
  }
}
menu.hide {
  animation: 0.5s ease-in-out hide\ menu;
}

0.18.17

Support An+B syntax and :nth-*() pseudo-classes in CSS

This adds support for the :nth-child(), :nth-last-child(), :nth-of-type(), and :nth-last-of-type() pseudo-classes to esbuild, which has the following consequences:
- The An+B syntax is now parsed, so parse errors are now reported
- An+B values inside these pseudo-classes are now pretty-printed (e.g. a leading + will be stripped because it's not in the AST)
- When minification is enabled, An+B values are reduced to equivalent but shorter forms (e.g. 2n+0 => 2n, 2n+1 => odd)
- Local CSS names in an of clause are now detected (e.g. in :nth-child(2n of :local(.foo)) the name foo is now renamed)
```
/* Original code */
.foo:nth-child(+2n+1 of :local(.bar)) {
  color: red;
}

/* Old output (with --loader=local-css) */
.stdin_foo:nth-child(+2n + 1 of :local(.bar)) {
  color: red;
}

/* New output (with --loader=local-css) */
.stdin_foo:nth-child(2n+1 of .stdin_bar) {
  color: red;
}
```
Adjust CSS nesting parser for IE7 hacks (#3272)

This fixes a regression with esbuild's treatment of IE7 hacks in CSS. CSS nesting allows selectors to be used where declarations are expected. There's an IE7 hack where prefixing a declaration with a * causes that declaration to only be applied in IE7 due to a bug in IE7's CSS parser. However, it's valid for nested CSS selectors to start with *. So esbuild was incorrectly parsing these declarations and anything following it up until the next { as a selector for a nested CSS rule. This release changes esbuild's parser to terminate the parsing of selectors for nested CSS rules when a ; is encountered to fix this edge case:
```
/* Original code */
.item {
  *width: 100%;
  height: 1px;
}

/* Old output */
.item {
  *width: 100%; height: 1px; {
  }
}

/* New output */
.item {
  *width: 100%;
  height: 1px;
}
```
Note that the syntax for CSS nesting is about to change again, so esbuild's CSS parser may still not be completely accurate with how browsers do and/or will interpret CSS nesting syntax. Expect additional updates to esbuild's CSS parser in the future to deal with upcoming CSS specification changes.
Adjust esbuild's warning about undefined imports for TypeScript import equals declarations (#3271)

In JavaScript, accessing a missing property on an import namespace object is supposed to result in a value of undefined at run-time instead of an error at compile-time. This is something that esbuild warns you about by default because doing this can indicate a bug with your code. For example:
```
// app.js
import * as styles from './styles'
console.log(styles.buton)
```
```
// styles.js
export let button = {}
```
If you bundle app.js with esbuild you will get this:
```
▲ [WARNING] Import "buton" will always be undefined because there is no matching export in "styles.js" [import-is-undefined]

    app.js:2:19:
      2 │ console.log(styles.buton)
        │                    ~~~~~
        ╵                    button

  Did you mean to import "button" instead?

    styles.js:1:11:
      1 │ export let button = {}
        ╵            ~~~~~~
```
However, there is TypeScript-only syntax for import equals declarations that can represent either a type import (which esbuild should ignore) or a value import (which esbuild should respect). Since esbuild doesn't have a type system, it tries to only respect import equals declarations that are actually used as values. Previously esbuild always generated this warning for unused imports referenced within import equals declarations even when the reference could be a type instead of a value. Starting with this release, esbuild will now only warn in this case if the import is actually used. Here is an example of some code that no longer causes an incorrect warning:
```
// app.ts
import * as styles from './styles'
import ButtonType = styles.Button
```
```
// styles.ts
export interface Button {}
```

0.18.16

Fix a regression with whitespace inside :is() (#3265)

The change to parse the contents of :is() in version 0.18.14 introduced a regression that incorrectly flagged the contents as a syntax error if the contents started with a whitespace token (for example div:is( .foo ) {}). This regression has been fixed.

0.18.15

Add the --serve-fallback= option (#2904)

The web server built into esbuild serves the latest in-memory results of the configured build. If the requested path doesn't match any in-memory build result, esbuild also provides the --servedir= option to tell esbuild to serve the requested path from that directory instead. And if the requested path doesn't match either of those things, esbuild will either automatically generate a directory listing (for directories) or return a 404 error.

Starting with this release, that last step can now be replaced with telling esbuild to serve a specific HTML file using the --serve-fallback= option. This can be used to provide a "not found" page for missing URLs. It can also be used to implement a single-page app that mutates the current URL and therefore requires the single app entry point to be served when the page is loaded regardless of whatever the current URL is.
Use the tsconfig field in package.json during extends resolution (#3247)

This release adds a feature from TypeScript 3.2 where if a tsconfig.json file specifies a package name in the extends field and that package's package.json file has a tsconfig field, the contents of that field are used in the search for the base tsconfig.json file.
Implement CSS nesting without :is() when possible (#1945)

Previously esbuild would always produce a warning when transforming nested CSS for a browser that doesn't support the :is() pseudo-class. This was because the nesting transform needs to generate an :is() in some complex cases which means the transformed CSS would then not work in that browser. However, the CSS nesting transform can often be done without generating an :is(). So with this release, esbuild will no longer warn when targeting browsers that don't support :is() in the cases where an :is() isn't needed to represent the nested CSS.

In addition, esbuild's nested CSS transform has been updated to avoid generating an :is() in cases where an :is() is preferable but there's a longer alternative that is also equivalent. This update means esbuild can now generate a combinatorial explosion of CSS for complex CSS nesting syntax when targeting browsers that don't support :is(). This combinatorial explosion is necessary to accurately represent the original semantics. For example:
```
/* Original code */
.first,
.second,
.third {
  & > & {
    color: red;
  }
}

/* Old output (with --target=chrome80) */
:is(.first, .second, .third) > :is(.first, .second, .third) {
  color: red;
}

/* New output (with --target=chrome80) */
.first > .first,
.first > .second,
.first > .third,
.second > .first,
.second > .second,
.second > .third,
.third > .first,
.third > .second,
.third > .third {
  color: red;
}
```
This change means you can now use CSS nesting with esbuild when targeting an older browser that doesn't support :is(). You'll now only get a warning from esbuild if you use complex CSS nesting syntax that esbuild can't represent in that older browser without using :is(). There are two such cases:
```
/* Case 1 */
a b {
  .foo & {
    color: red;
  }
}

/* Case 2 */
a {
  > b& {
    color: red;
  }
}
```
These two cases still need to use :is(), both for different reasons, and cannot be used when targeting an older browser that doesn't support :is():
```
/* Case 1 */
.foo :is(a b) {
  color: red;
}

/* Case 2 */
a > a:is(b) {
  color: red;
}
```

Automatically lower inset in CSS for older browsers

With this release, esbuild will now automatically expand the inset property to the top, right, bottom, and left properties when esbuild's target is set to a browser that doesn't support inset:

/* Original code */
.app {
  position: absolute;
  inset: 10px 20px;
}

/* Old output (with --target=chrome80) */
.app {
  position: absolute;
  inset: 10px 20px;
}

/* New output (with --target=chrome80) */
.app {
  position: absolute;
  top: 10px;
  right: 20px;
  bottom: 10px;
  left: 20px;
}

Add support for the new @starting-style CSS rule (#3249)

This at rule allow authors to start CSS transitions on first style update. That is, you can now make the transition take effect when the display property changes from none to block.
```
/* Original code */
@starting-style {
  h1 {
    background-color: transparent;
  }
}

/* Output */
@starting-style{h1{background-color:transparent}}
```
This was contributed by @yisibl.

0.18.14

Implement local CSS names (#20)

This release introduces two new loaders called global-css and local-css and two new pseudo-class selectors :local() and :global(). This is a partial implementation of the popular CSS modules approach for avoiding unintentional name collisions in CSS. I'm not calling this feature "CSS modules" because although some people in the community call it that, other people in the community have started using "CSS modules" to refer to something completely different and now CSS modules is an overloaded term.

Here's how this new local CSS name feature works with esbuild:
- Identifiers that look like .className and #idName are global with the global-css loader and local with the local-css loader. Global identifiers are the same across all files (the way CSS normally works) but local identifiers are different between different files. If two separate CSS files use the same local identifier .button, esbuild will automatically rename one of them so that they don't collide. This is analogous to how esbuild automatically renames JS local variables with the same name in separate JS files to avoid name collisions.
- It only makes sense to use local CSS names with esbuild when you are also using esbuild's bundler to bundle JS files that import CSS files. When you do that, esbuild will generate one export for each local name in the CSS file. The JS code can import these names and use them when constructing HTML DOM. For example:
```
// app.js
import { outerShell } from './app.css'
const div = document.createElement('div')
div.className = outerShell
document.body.appendChild(div)
```
```
/* app.css */
.outerShell {
  position: absolute;
  inset: 0;
}
```
  When you bundle this with esbuild app.js --bundle --loader:.css=local-css --outdir=out you'll now get this (notice how the local CSS name outerShell has been renamed):
```
// out/app.js
(() => {
  // app.css
  var outerShell = "app_outerShell";

  // app.js
  var div = document.createElement("div");
  div.className = outerShell;
  document.body.appendChild(div);
})();
```
```
/* out/app.css */
.app_outerShell {
  position: absolute;
  inset: 0;
}
```
  This feature only makes sense to use when bundling is enabled both because your code needs to import the renamed local names so that it can use them, and because esbuild needs to be able to process all CSS files containing local names in a single bundling operation so that it can successfully rename conflicting local names to avoid collisions.
- If you are in a global CSS file (with the global-css loader) you can create a local name using :local(), and if you are in a local CSS file (with the local-css loader) you can create a global name with :global(). So the choice of the global-css loader vs. the local-css loader just sets the default behavior for identifiers, but you can override it on a case-by-case basis as necessary. For example:
```
:local(.button) {
  color: red;
}
:global(.button) {
  color: blue;
}
```
  Processing this CSS file with esbuild with either the global-css or local-css loader will result in something like this:
```
.stdin_button {
  color: red;
}
.button {
  color: blue;
}
```
- The names that esbuild generates for local CSS names are an implementation detail and are not intended to be hard-coded anywhere. The only way you should be referencing the local CSS names in your JS or HTML is with an import statement in JS that is bundled with esbuild, as demonstrated above. For example, when --minify is enabled esbuild will use a different name generation algorithm which generates names that are as short as possible (analogous to how esbuild minifies local identifiers in JS).
- You can easily use both global CSS files and local CSS files simultaneously if you give them different file extensions. For example, you could pass --loader:.css=global-css and --loader:.module.css=local-css to esbuild so that .css files still use global names by default but .module.css files use local names by default.
- Keep in mind that the css loader is different than the global-css loader. The :local and :global annotations are not enabled with the css loader and will be passed through unchanged. This allows you to have the option of using esbuild to process CSS containing while preserving these annotations. It also means that local CSS names are disabled by default for now (since the css loader is currently the default for CSS files). The :local and :global syntax may be enabled by default in a future release.
Note that esbuild's implementation does not currently have feature parity with other implementations of modular CSS in similar tools. This is only a preliminary release with a partial implementation that includes some basic behavior to get the process started. Additional behavior may be added in future releases. In particular, this release does not implement:
- The composes pragma
- Tree shaking for unused local CSS
- Local names for keyframe animations, grid lines, @container, @counter-style, etc.
Issue #20 (the issue for this feature) is esbuild's most-upvoted issue! While this release still leaves that issue open, it's an important first step in that direction.
Parse :is, :has, :not, and :where in CSS

With this release, esbuild will now parse the contents of these pseudo-class selectors as a selector list. This means you will now get syntax warnings within these selectors for invalid selector syntax. It also means that esbuild's CSS nesting transform behaves slightly differently than before because esbuild is now operating on an AST instead of a token stream. For example:
```
/* Original code */
div {
  :where(.foo&) {
    color: red;
  }
}

/* Old output (with --target=chrome90) */
:where(.foo:is(div)) {
  color: red;
}

/* New output (with --target=chrome90) */
:where(div.foo) {
  color: red;
}
```

0.18.13

Add the --drop-labels= option (#2398)

If you want to conditionally disable some development-only code and have it not be present in the final production bundle, right now the most straightforward way of doing this is to use the --define: flag along with a specially-named global variable. For example, consider the following code:
```
function main() {
  DEV && doAnExpensiveCheck()
}
```
You can build this for development and production like this:
- Development: esbuild --define:DEV=true
- Production: esbuild --define:DEV=false
One drawback of this approach is that the resulting code crashes if you don't provide a value for DEV with --define:. In practice this isn't that big of a problem, and there are also various ways to work around this.

However, another approach that avoids this drawback is to use JavaScript label statements instead. That's what the --drop-labels= flag implements. For example, consider the following code:
```
function main() {
  DEV: doAnExpensiveCheck()
}
```
With this release, you can now build this for development and production like this:
- Development: esbuild
- Production: esbuild --drop-labels=DEV
This means that code containing optional development-only checks can now be written such that it's safe to run without any additional configuration. The --drop-labels= flag takes comma-separated list of multiple label names to drop.
Avoid causing unhandledRejection during shutdown (#3219)

All pending esbuild JavaScript API calls are supposed to fail if esbuild's underlying child process is unexpectedly terminated. This can happen if SIGINT is sent to the parent node process with Ctrl+C, for example. Previously doing this could also cause an unhandled promise rejection when esbuild attempted to communicate this failure to its own child process that no longer exists. This release now swallows this communication failure, which should prevent this internal unhandled promise rejection. This change means that you can now use esbuild's JavaScript API with a custom SIGINT handler that extends the lifetime of the node process without esbuild's internals causing an early exit due to an unhandled promise rejection.
Update browser compatibility table scripts

The scripts that esbuild uses to compile its internal browser compatibility table have been overhauled. Briefly:
- Converted from JavaScript to TypeScript
- Fixed some bugs that resulted in small changes to the table
- Added caniuse-lite and @mdn/browser-compat-data as new data sources (replacing manually-copied information)
This change means it's now much easier to keep esbuild's internal compatibility tables up to date. You can review the table changes here if you need to debug something about this change:
- JS table changes
- CSS table changes

0.18.12

Fix a panic with const enum inside parentheses (#3205)

This release fixes an edge case where esbuild could potentially panic if a TypeScript const enum statement was used inside of a parenthesized expression and was followed by certain other scope-related statements. Here's a minimal example that triggers this edge case:
```
(() => {
  const enum E { a };
  () => E.a
})
```
Allow a newline in the middle of TypeScript export type statement (#3225)

Previously esbuild incorrectly rejected the following valid TypeScript code:
```
export type
{ T };

export type
* as foo from 'bar';
```
Code that uses a newline after export type is now allowed starting with this release.
Fix cross-module inlining of string enums (#3210)

A refactoring typo in version 0.18.9 accidentally introduced a regression with cross-module inlining of string enums when combined with computed property accesses. This regression has been fixed.
Rewrite .js to .ts inside packages with exports (#3201)

Packages with the exports field are supposed to disable node's path resolution behavior that allows you to import a file with a different extension than the one in the source code (for example, importing foo/bar to get foo/bar.js). And TypeScript has behavior where you can import a non-existent .js file and you will get the .ts file instead. Previously the presence of the exports field caused esbuild to disable all extension manipulation stuff which included both node's implicit file extension searching and TypeScript's file extension swapping. However, TypeScript appears to always apply file extension swapping even in this case. So with this release, esbuild will now rewrite .js to .ts even inside packages with exports.
Fix a redirect edge case in esbuild's development server (#3208)

The development server canonicalizes directory URLs by adding a trailing slash. For example, visiting /about redirects to /about/ if /about/index.html would be served. However, if the requested path begins with two slashes, then the redirect incorrectly turned into a protocol-relative URL. For example, visiting //about redirected to //about/ which the browser turns into http://about/. This release fixes the bug by canonicalizing the URL path when doing this redirect.

0.18.11

Fix a TypeScript code generation edge case (#3199)

This release fixes a regression in version 0.18.4 where using a TypeScript namespace that exports a class declaration combined with --keep-names and a --target of es2021 or earlier could cause esbuild to export the class from the namespace using an incorrect name (notice the assignment to X2._Y vs. X2.Y):

// Original code

// Old output (with --keep-names --target=es2021)
var X;
((X2) => {
  const _Y = class _Y {
  };
  __name(_Y, "Y");
  let Y = _Y;
  X2._Y = _Y;
})(X || (X = {}));

// New output (with --keep-names --target=es2021)
var X;
((X2) => {
  const _Y = class _Y {
  };
  __name(_Y, "Y");
  let Y = _Y;
  X2.Y = _Y;
})(X || (X = {}));

0.18.10

Fix a tree-shaking bug that removed side effects (#3195)

This fixes a regression in version 0.18.4 where combining --minify-syntax with --keep-names could cause expressions with side effects after a function declaration to be considered side-effect free for tree shaking purposes. The reason was because --keep-names generates an expression statement containing a call to a helper function after the function declaration with a special flag that makes the function call able to be tree shaken, and then --minify-syntax could potentially merge that expression statement with following expressions without clearing the flag. This release fixes the bug by clearing the flag when merging expression statements together.
Fix an incorrect warning about CSS nesting (#3197)

A warning is currently generated when transforming nested CSS to a browser that doesn't support :is() because transformed nested CSS may need to use that feature to represent nesting. This was previously always triggered when an at-rule was encountered in a declaration context. Typically the only case you would encounter this is when using CSS nesting within a selector rule. However, there is a case where that's not true: when using a margin at-rule such as @top-left within @page. This release avoids incorrectly generating a warning in this case by checking that the at-rule is within a selector rule before generating a warning.

0.18.9

Fix await using declarations inside async generator functions

I forgot about the new await using declarations when implementing lowering for async generator functions in the previous release. This change fixes the transformation of await using declarations when they are inside lowered async generator functions:

// Original code
async function* foo() {
  await using x = await y
}

// Old output (with --supported:async-generator=false)
function foo() {
  return __asyncGenerator(this, null, function* () {
    await using x = yield new __await(y);
  });
}

// New output (with --supported:async-generator=false)
function foo() {
  return __asyncGenerator(this, null, function* () {
    var _stack = [];
    try {
      const x = __using(_stack, yield new __await(y), true);
    } catch (_) {
      var _error = _, _hasError = true;
    } finally {
      var _promise = __callDispose(_stack, _error, _hasError);
      _promise && (yield new __await(_promise));
    }
  });
}

Insert some prefixed CSS properties when appropriate (#3122)

With this release, esbuild will now insert prefixed CSS properties in certain cases when the target setting includes browsers that require a certain prefix. This is currently done for the following properties:
- appearance: *; => -webkit-appearance: *; -moz-appearance: *;
- backdrop-filter: *; => -webkit-backdrop-filter: *;
- background-clip: text => -webkit-background-clip: text;
- box-decoration-break: *; => -webkit-box-decoration-break: *;
- clip-path: *; => -webkit-clip-path: *;
- font-kerning: *; => -webkit-font-kerning: *;
- hyphens: *; => -webkit-hyphens: *;
- initial-letter: *; => -webkit-initial-letter: *;
- mask-image: *; => -webkit-mask-image: *;
- mask-origin: *; => -webkit-mask-origin: *;
- mask-position: *; => -webkit-mask-position: *;
- mask-repeat: *; => -webkit-mask-repeat: *;
- mask-size: *; => -webkit-mask-size: *;
- position: sticky; => position: -webkit-sticky;
- print-color-adjust: *; => -webkit-print-color-adjust: *;
- tab-size: *; => -moz-tab-size: *; -o-tab-size: *;
- text-decoration-color: *; => -webkit-text-decoration-color: *; -moz-text-decoration-color: *;
- text-decoration-line: *; => -webkit-text-decoration-line: *; -moz-text-decoration-line: *;
- text-decoration-skip: *; => -webkit-text-decoration-skip: *;
- text-emphasis-color: *; => -webkit-text-emphasis-color: *;
- text-emphasis-position: *; => -webkit-text-emphasis-position: *;
- text-emphasis-style: *; => -webkit-text-emphasis-style: *;
- text-orientation: *; => -webkit-text-orientation: *;
- text-size-adjust: *; => -webkit-text-size-adjust: *; -ms-text-size-adjust: *;
- user-select: *; => -webkit-user-select: *; -moz-user-select: *; -ms-user-select: *;
Here is an example:
```
/* Original code */
div {
  mask-image: url(x.png);
}

/* Old output (with --target=chrome99) */
div {
  mask-image: url(x.png);
}

/* New output (with --target=chrome99) */
div {
  -webkit-mask-image: url(x.png);
  mask-image: url(x.png);
}
```
Browser compatibility data was sourced from the tables on https://caniuse.com. Support for more CSS properties can be added in the future as appropriate.
Fix an obscure identifier minification bug (#2809)

Function declarations in nested scopes behave differently depending on whether or not "use strict" is present. To avoid generating code that behaves differently depending on whether strict mode is enabled or not, esbuild transforms nested function declarations into variable declarations. However, there was a bug where the generated variable name was not being recorded as declared internally, which meant that it wasn't being renamed correctly by the minifier and could cause a name collision. This bug has been fixed:
```
// Original code
const n = ''
for (let i of [0,1]) {
  function f () {}
}

// Old output (with --minify-identifiers --format=esm)
const f = "";
for (let o of [0, 1]) {
  let n = function() {
  };
  var f = n;
}

// New output (with --minify-identifiers --format=esm)
const f = "";
for (let o of [0, 1]) {
  let n = function() {
  };
  var t = n;
}
```
Fix a bug in esbuild's compatibility table script (#3179)

Setting esbuild's target to a specific JavaScript engine tells esbuild to use the JavaScript syntax feature compatibility data from https://kangax.github.io/compat-table/es6/ for that engine to determine which syntax features to allow. However, esbuild's script that builds this internal compatibility table had a bug that incorrectly ignores tests for engines that still have outstanding implementation bugs which were never fixed. This change fixes this bug with the script.

The only case where this changed the information in esbuild's internal compatibility table is that the hermes target is marked as no longer supporting destructuring. This is because there is a failing destructuring-related test for Hermes on https://kangax.github.io/compat-table/es6/. If you want to use destructuring with Hermes anyway, you can pass --supported:destructuring=true to esbuild to override the hermes target and force esbuild to accept this syntax.

This fix was contributed by @ArrayZoneYour.

0.18.8

Implement transforming async generator functions (#2780)

With this release, esbuild will now transform async generator functions into normal generator functions when the configured target environment doesn't support them. These functions behave similar to normal generator functions except that they use the Symbol.asyncIterator interface instead of the Symbol.iterator interface and the iteration methods return promises. Here's an example (helper functions are omitted):

// Original code
async function* foo() {
  yield Promise.resolve(1)
  await new Promise(r => setTimeout(r, 100))
  yield *[Promise.resolve(2)]
}
async function bar() {
  for await (const x of foo()) {
    console.log(x)
  }
}
bar()

// New output (with --target=es6)
function foo() {
  return __asyncGenerator(this, null, function* () {
    yield Promise.resolve(1);
    yield new __await(new Promise((r) => setTimeout(r, 100)));
    yield* __yieldStar([Promise.resolve(2)]);
  });
}
function bar() {
  return __async(this, null, function* () {
    try {
      for (var iter = __forAwait(foo()), more, temp, error; more = !(temp = yield iter.next()).done; more = false) {
        const x = temp.value;
        console.log(x);
      }
    } catch (temp) {
      error = [temp];
    } finally {
      try {
        more && (temp = iter.return) && (yield temp.call(iter));
      } finally {
        if (error)
          throw error[0];
      }
    }
  });
}
bar();

This is an older feature that was added to JavaScript in ES2018 but I didn't implement the transformation then because it's a rarely-used feature. Note that esbuild already added support for transforming for await loops (the other part of the asynchronous iteration proposal) a year ago, so support for asynchronous iteration should now be complete.

I have never used this feature myself and code that uses this feature is hard to come by, so this transformation has not yet been tested on real-world code. If you do write code that uses this feature, please let me know if esbuild's async generator transformation doesn't work with your code.

0.18.7

Add support for using declarations in TypeScript 5.2+ (#3191)

TypeScript 5.2 (due to be released in August of 2023) will introduce using declarations, which will allow you to automatically dispose of the declared resources when leaving the current scope. You can read the TypeScript PR for this feature for more information. This release of esbuild adds support for transforming this syntax to target environments without support for using declarations (which is currently all targets other than esnext). Here's an example (helper functions are omitted):
```
// Original code
class Foo {
  [Symbol.dispose]() {
    console.log('cleanup')
  }
}
using foo = new Foo;
foo.bar();

// New output (with --target=es6)
var _stack = [];
try {
  var Foo = class {
    [Symbol.dispose]() {
      console.log("cleanup");
    }
  };
  var foo = __using(_stack, new Foo());
  foo.bar();
} catch (_) {
  var _error = _, _hasError = true;
} finally {
  __callDispose(_stack, _error, _hasError);
}
```
The injected helper functions ensure that the method named Symbol.dispose is called on new Foo when control exits the scope. Note that as with all new JavaScript APIs, you'll need to polyfill Symbol.dispose if it's not present before you use it. This is not something that esbuild does for you because esbuild only handles syntax, not APIs. Polyfilling it can be done with something like this:
```
Symbol.dispose ||= Symbol('Symbol.dispose')
```
This feature also introduces await using declarations which are like using declarations but they call await on the disposal method (not on the initializer). Here's an example (helper functions are omitted):
```
// Original code
class Foo {
  async [Symbol.asyncDispose]() {
    await new Promise(done => {
      setTimeout(done, 1000)
    })
    console.log('cleanup')
  }
}
await using foo = new Foo;
foo.bar();

// New output (with --target=es2022)
var _stack = [];
try {
  var Foo = class {
    async [Symbol.asyncDispose]() {
      await new Promise((done) => {
        setTimeout(done, 1e3);
      });
      console.log("cleanup");
    }
  };
  var foo = __using(_stack, new Foo(), true);
  foo.bar();
} catch (_) {
  var _error = _, _hasError = true;
} finally {
  var _promise = __callDispose(_stack, _error, _hasError);
  _promise && await _promise;
}
```
The injected helper functions ensure that the method named Symbol.asyncDispose is called on new Foo when control exits the scope, and that the returned promise is awaited. Similarly to Symbol.dispose, you'll also need to polyfill Symbol.asyncDispose before you use it.
Add a --line-limit= flag to limit line length (#3170)

Long lines are common in minified code. However, many tools and text editors can't handle long lines. This release introduces the --line-limit= flag to tell esbuild to wrap lines longer than the provided number of bytes. For example, --line-limit=80 tells esbuild to insert a newline soon after a given line reaches 80 bytes in length. This setting applies to both JavaScript and CSS, and works even when minification is disabled. Note that turning this setting on will make your files bigger, as the extra newlines take up additional space in the file (even after gzip compression).

0.18.6

Fix tree-shaking of classes with decorators (#3164)

This release fixes a bug where esbuild incorrectly allowed tree-shaking on classes with decorators. Each decorator is a function call, so classes with decorators must never be tree-shaken. This bug was a regression that was unintentionally introduced in version 0.18.2 by the change that enabled tree-shaking of lowered private fields. Previously decorators were always lowered, and esbuild always considered the automatically-generated decorator code to be a side effect. But this is no longer the case now that esbuild analyzes side effects using the AST before lowering takes place. This bug was fixed by considering any decorator a side effect.
Fix a minification bug involving function expressions (#3125)

When minification is enabled, esbuild does limited inlining of const symbols at the top of a scope. This release fixes a bug where inlineable symbols were incorrectly removed assuming that they were inlined. They may not be inlined in cases where they were referenced by earlier constants in the body of a function expression. The declarations involved in these edge cases are now kept instead of being removed:
```
// Original code
{
  const fn = () => foo
  const foo = 123
  console.log(fn)
}

// Old output (with --minify-syntax)
console.log((() => foo)());

// New output (with --minify-syntax)
{
  const fn = () => foo, foo = 123;
  console.log(fn);
}
```

0.18.5

Implement auto accessors (#3009)

This release implements the new auto-accessor syntax from the upcoming JavaScript decorators proposal. The auto-accessor syntax looks like this:

class Foo {
  accessor foo;
  static accessor bar;
}
new Foo().foo = Foo.bar;

This syntax is not yet a part of JavaScript but it was added to TypeScript in version 4.9. More information about this feature can be found in microsoft/TypeScript#49705. Auto-accessors will be transformed if the target is set to something other than esnext:

// Output (with --target=esnext)
class Foo {
  accessor foo;
  static accessor bar;
}
new Foo().foo = Foo.bar;

// Output (with --target=es2022)
class Foo {
  #foo;
  get foo() {
    return this.#foo;
  }
  set foo(_) {
    this.#foo = _;
  }
  static #bar;
  static get bar() {
    return this.#bar;
  }
  static set bar(_) {
    this.#bar = _;
  }
}
new Foo().foo = Foo.bar;

// Output (with --target=es2021)
var _foo, _bar;
class Foo {
  constructor() {
    __privateAdd(this, _foo, void 0);
  }
  get foo() {
    return __privateGet(this, _foo);
  }
  set foo(_) {
    __privateSet(this, _foo, _);
  }
  static get bar() {
    return __privateGet(this, _bar);
  }
  static set bar(_) {
    __privateSet(this, _bar, _);
  }
}
_foo = new WeakMap();
_bar = new WeakMap();
__privateAdd(Foo, _bar, void 0);
new Foo().foo = Foo.bar;

You can also now use auto-accessors with esbuild's TypeScript experimental decorator transformation, which should behave the same as decorating the underlying getter/setter pair.

Please keep in mind that this syntax is not yet part of JavaScript. This release enables auto-accessors in .js files with the expectation that it will be a part of JavaScript soon. However, esbuild may change or remove this feature in the future if JavaScript ends up changing or removing this feature. Use this feature with caution for now.

Pass through JavaScript decorators (#104)

In this release, esbuild now parses decorators from the upcoming JavaScript decorators proposal and passes them through to the output unmodified (as long as the language target is set to esnext). Transforming JavaScript decorators to environments that don't support them has not been implemented yet. The only decorator transform that esbuild currently implements is still the TypeScript experimental decorator transform, which only works in .ts files and which requires "experimentalDecorators": true in your tsconfig.json file.
Static fields with assign semantics now use static blocks if possible

Setting useDefineForClassFields to false in TypeScript requires rewriting class fields to assignment statements. Previously this was done by removing the field from the class body and adding an assignment statement after the class declaration. However, this also caused any private fields to also be lowered by necessity (in case a field initializer uses a private symbol, either directly or indirectly). This release changes this transform to use an inline static block if it's supported, which avoids needing to lower private fields in this scenario:
```
// Original code
class Test {
  static #foo = 123
  static bar = this.#foo
}

// Old output (with useDefineForClassFields=false)
var _foo;
const _Test = class _Test {
};
_foo = new WeakMap();
__privateAdd(_Test, _foo, 123);
_Test.bar = __privateGet(_Test, _foo);
let Test = _Test;

// New output (with useDefineForClassFields=false)
class Test {
  static #foo = 123;
  static {
    this.bar = this.#foo;
  }
}
```
Fix TypeScript experimental decorators combined with --mangle-props (#3177)

Previously using TypeScript experimental decorators combined with the --mangle-props setting could result in a crash, as the experimental decorator transform was not expecting a mangled property as a class member. This release fixes the crash so you can now combine both of these features together safely.

0.18.4

Bundling no longer unnecessarily transforms class syntax (#1360, #1328, #1524, #2416)

When bundling, esbuild automatically converts top-level class statements to class expressions. Previously this conversion had the unfortunate side-effect of also transforming certain other class-related syntax features to avoid correctness issues when the references to the class name within the class body. This conversion has been reworked to avoid doing this:
```
// Original code
export class Foo {
  static foo = () => Foo
}

// Old output (with --bundle)
var _Foo = class {
};
var Foo = _Foo;
__publicField(Foo, "foo", () => _Foo);

// New output (with --bundle)
var Foo = class _Foo {
  static foo = () => _Foo;
};
```
This conversion process is very complicated and has many edge cases (including interactions with static fields, static blocks, private class properties, and TypeScript experimental decorators). It should already be pretty robust but a change like this may introduce new unintentional behavior. Please report any issues with this upgrade on the esbuild bug tracker.

You may be wondering why esbuild needs to do this at all. One reason to do this is that esbuild's bundler sometimes needs to lazily-evaluate a module. For example, a module may end up being both the target of a dynamic import() call and a static import statement. Lazy module evaluation is done by wrapping the top-level module code in a closure. To avoid a performance hit for static import statements, esbuild stores top-level exported symbols outside of the closure and references them directly instead of indirectly.

Another reason to do this is that multiple JavaScript VMs have had and continue to have performance issues with TDZ (i.e. "temporal dead zone") checks. These checks validate that a let, or const, or class symbol isn't used before it's initialized. Here are two issues with well-known VMs:
- V8: https://bugs.chromium.org/p/v8/issues/detail?id=13723 (10% slowdown)
- JavaScriptCore: https://bugs.webkit.org/show_bug.cgi?id=199866 (1,000% slowdown!)
JavaScriptCore had a severe performance issue as their TDZ implementation had time complexity that was quadratic in the number of variables needing TDZ checks in the same scope (with the top-level scope typically being the worst offender). V8 has ongoing issues with TDZ checks being present throughout the code their JIT generates even when they have already been checked earlier in the same function or when the function in question has already been run (so the checks have already happened).

Due to esbuild's parallel architecture, esbuild both a) needs to convert class statements into class expressions during parsing and b) doesn't yet know whether this module will need to be lazily-evaluated or not in the parser. So esbuild always does this conversion during bundling in case it's needed for correctness (and also to avoid potentially catastrophic performance issues due to bundling creating a large scope with many TDZ variables).
Enforce TDZ errors in computed class property keys (#2045)

JavaScript allows class property keys to be generated at run-time using code, like this:
```
class Foo {
  static foo = 'foo'
  static [Foo.foo + '2'] = 2
}
```
Previously esbuild treated references to the containing class name within computed property keys as a reference to the partially-initialized class object. That meant code that attempted to reference properties of the class object (such as the code above) would get back undefined instead of throwing an error.

This release rewrites references to the containing class name within computed property keys into code that always throws an error at run-time, which is how this JavaScript code is supposed to work. Code that does this will now also generate a warning. You should never write code like this, but it now should be more obvious when incorrect code like this is written.

Fix an issue with experimental decorators and static fields (#2629)

This release also fixes a bug regarding TypeScript experimental decorators and static class fields which reference the enclosing class name in their initializer. This affected top-level classes when bundling was enabled. Previously code that does this could crash because the class name wasn't initialized yet. This case should now be handled correctly:

// Original code
class Foo {
  @someDecorator
  static foo = 'foo'
  static bar = Foo.foo.length
}

// Old output
const _Foo = class {
  static foo = "foo";
  static bar = _Foo.foo.length;
};
let Foo = _Foo;
__decorateClass([
  someDecorator
], Foo, "foo", 2);

// New output
const _Foo = class _Foo {
  static foo = "foo";
  static bar = _Foo.foo.length;
};
__decorateClass([
  someDecorator
], _Foo, "foo", 2);
let Foo = _Foo;

Fix a minification regression with negative numeric properties (#3169)

Version 0.18.0 introduced a regression where computed properties with negative numbers were incorrectly shortened into a non-computed property when minification was enabled. This regression has been fixed:

// Original code
x = {
  [1]: 1,
  [-1]: -1,
  [NaN]: NaN,
  [Infinity]: Infinity,
  [-Infinity]: -Infinity,
}

// Old output (with --minify)
x={1:1,-1:-1,NaN:NaN,1/0:1/0,-1/0:-1/0};

// New output (with --minify)
x={1:1,[-1]:-1,NaN:NaN,[1/0]:1/0,[-1/0]:-1/0};

0.18.3

Fix a panic due to empty static class blocks (#3161)

This release fixes a bug where an internal invariant that was introduced in the previous release was sometimes violated, which then caused a panic. It happened when bundling code containing an empty static class block with both minification and bundling enabled.

0.18.2

Lower static blocks when static fields are lowered (#2800, #2950, #3025)

This release fixes a bug where esbuild incorrectly did not lower static class blocks when static class fields needed to be lowered. For example, the following code should print 1 2 3 but previously printed 2 1 3 instead due to this bug:

// Original code
class Foo {
  static x = console.log(1)
  static { console.log(2) }
  static y = console.log(3)
}

// Old output (with --supported:class-static-field=false)
class Foo {
  static {
    console.log(2);
  }
}
__publicField(Foo, "x", console.log(1));
__publicField(Foo, "y", console.log(3));

// New output (with --supported:class-static-field=false)
class Foo {
}
__publicField(Foo, "x", console.log(1));
console.log(2);
__publicField(Foo, "y", console.log(3));

Use static blocks to implement --keep-names on classes (#2389)

This change fixes a bug where the name property could previously be incorrect within a class static context when using --keep-names. The problem was that the name property was being initialized after static blocks were run instead of before. This has been fixed by moving the name property initializer into a static block at the top of the class body:
```
// Original code
if (typeof Foo === 'undefined') {
  let Foo = class {
    static test = this.name
  }
  console.log(Foo.test)
}

// Old output (with --keep-names)
if (typeof Foo === "undefined") {
  let Foo2 = /* @__PURE__ */ __name(class {
    static test = this.name;
  }, "Foo");
  console.log(Foo2.test);
}

// New output (with --keep-names)
if (typeof Foo === "undefined") {
  let Foo2 = class {
    static {
      __name(this, "Foo");
    }
    static test = this.name;
  };
  console.log(Foo2.test);
}
```
This change was somewhat involved, especially regarding what esbuild considers to be side-effect free. Some unused classes that weren't removed by tree shaking in previous versions of esbuild may now be tree-shaken. One example is classes with static private fields that are transformed by esbuild into code that doesn't use JavaScript's private field syntax. Previously esbuild's tree shaking analysis ran on the class after syntax lowering, but with this release it will run on the class before syntax lowering, meaning it should no longer be confused by class mutations resulting from automatically-generated syntax lowering code.

0.18.1

Fill in null entries in input source maps (#3144)

If esbuild bundles input files with source maps and those source maps contain a sourcesContent array with null entries, esbuild previously copied those null entries over to the output source map. With this release, esbuild will now attempt to fill in those null entries by looking for a file on the file system with the corresponding name from the sources array. This matches esbuild's existing behavior that automatically generates the sourcesContent array from the file system if the entire sourcesContent array is missing.
Support /* @__KEY__ */ comments for mangling property names (#2574)

Property mangling is an advanced feature that enables esbuild to minify certain property names, even though it's not possible to automatically determine that it's safe to do so. The safe property names are configured via regular expression such as --mangle-props=_$ (mangle all properties ending in _).

Sometimes it's desirable to also minify strings containing property names, even though it's not possible to automatically determine which strings are property names. This release makes it possible to do this by annotating those strings with /* @__KEY__ */. This is a convention that Terser added earlier this year, and which esbuild is now following too: terser/terser#1365. Using it looks like this:
```
// Original code
console.log(
  [obj.mangle_, obj.keep],
  [obj.get('mangle_'), obj.get('keep')],
  [obj.get(/* @__KEY__ */ 'mangle_'), obj.get(/* @__KEY__ */ 'keep')],
)

// Old output (with --mangle-props=_$)
console.log(
  [obj.a, obj.keep],
  [obj.get("mangle_"), obj.get("keep")],
  [obj.get(/* @__KEY__ */ "mangle_"), obj.get(/* @__KEY__ */ "keep")]
);

// New output (with --mangle-props=_$)
console.log(
  [obj.a, obj.keep],
  [obj.get("mangle_"), obj.get("keep")],
  [obj.get(/* @__KEY__ */ "a"), obj.get(/* @__KEY__ */ "keep")]
);
```
Support /* @__NO_SIDE_EFFECTS__ */ comments for functions (#3149)

Rollup has recently added support for /* @__NO_SIDE_EFFECTS__ */ annotations before functions to indicate that calls to these functions can be removed if the result is unused (i.e. the calls can be assumed to have no side effects). This release adds basic support for these to esbuild as well, which means esbuild will now parse these comments in input files and preserve them in output files. This should help people that use esbuild in combination with Rollup.

Note that this doesn't necessarily mean esbuild will treat these calls as having no side effects, as esbuild's parallel architecture currently isn't set up to enable this type of cross-file tree-shaking information (tree-shaking decisions regarding a function call are currently local to the file they appear in). If you want esbuild to consider a function call to have no side effects, make sure you continue to annotate the function call with /* @__PURE__ */ (which is the previously-established convention for communicating this).

0.18.0

This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild in your package.json file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.17.0 or ~0.17.0. See npm's documentation about semver for more information.

The breaking changes in this release mainly focus on fixing some long-standing issues with esbuild's handling of tsconfig.json files. Here are all the changes in this release, in detail:

Add a way to try esbuild online (#797)

There is now a way to try esbuild live on esbuild's website without installing it: https://esbuild.github.io/try/. In addition to being able to more easily evaluate esbuild, this should also make it more efficient to generate esbuild bug reports. For example, you can use it to compare the behavior of different versions of esbuild on the same input. The state of the page is stored in the URL for easy sharing. Many thanks to @hyrious for creating https://hyrious.me/esbuild-repl/, which was the main inspiration for this addition to esbuild's website.

Two forms of build options are supported: either CLI-style (example) or JS-style (example). Both are converted into a JS object that's passed to esbuild's WebAssembly API. The CLI-style argument parser is a custom one that simulates shell quoting rules, and the JS-style argument parser is also custom and parses a superset of JSON (basically JSON5 + regular expressions). So argument parsing is an approximate simulation of what happens for real but hopefully it should be close enough.
Changes to esbuild's tsconfig.json support (#3019):

This release makes the following changes to esbuild's tsconfig.json support:
- Using experimental decorators now requires "experimentalDecorators": true (#104)
  
  Previously esbuild would always compile decorators in TypeScript code using TypeScript's experimental decorator transform. Now that standard JavaScript decorators are close to being finalized, esbuild will now require you to use "experimentalDecorators": true to do this. This new requirement makes it possible for esbuild to introduce a transform for standard JavaScript decorators in TypeScript code in the future. Such a transform has not been implemented yet, however.
- TypeScript's target no longer affects esbuild's target (#2628)
  
  Some people requested that esbuild support TypeScript's target setting, so support for it was added (in version 0.12.4). However, esbuild supports reading from multiple tsconfig.json files within a single build, which opens up the possibility that different files in the build have different language targets configured. There isn't really any reason to do this and it can lead to unexpected results. So with this release, the target setting in tsconfig.json will no longer affect esbuild's own target setting. You will have to use esbuild's own target setting instead (which is a single, global value).
- TypeScript's jsx setting no longer causes esbuild to preserve JSX syntax (#2634)
  
  TypeScript has a setting called jsx that controls how to transform JSX into JS. The tool-agnostic transform is called react, and the React-specific transform is called react-jsx (or react-jsxdev). There is also a setting called preserve which indicates JSX should be passed through untransformed. Previously people would run esbuild with "jsx": "preserve" in their tsconfig.json files and then be surprised when esbuild preserved their JSX. So with this release, esbuild will now ignore "jsx": "preserve" in tsconfig.json files. If you want to preserve JSX syntax with esbuild, you now have to use --jsx=preserve.
  
  Note: Some people have suggested that esbuild's equivalent jsx setting override the one in tsconfig.json. However, some projects need to legitimately have different files within the same build use different transforms (i.e. react vs. react-jsx) and having esbuild's global jsx setting override tsconfig.json would prevent this from working. This release ignores "jsx": "preserve" but still allows other jsx values in tsconfig.json files to override esbuild's global jsx setting to keep the ability for multiple files within the same build to use different transforms.
- useDefineForClassFields behavior has changed (#2584, #2993)
  
  Class fields in TypeScript look like this (x is a class field):
```
class Foo {
  x = 123
}
```
  TypeScript has legacy behavior that uses assignment semantics instead of define semantics for class fields when useDefineForClassFields is enabled (in which case class fields in TypeScript behave differently than they do in JavaScript, which is arguably "wrong").
  
  This legacy behavior exists because TypeScript added class fields to TypeScript before they were added to JavaScript. The TypeScript team decided to go with assignment semantics and shipped their implementation. Much later on TC39 decided to go with define semantics for class fields in JavaScript instead. This behaves differently if the base class has a setter with the same name:
```
class Base {
  set x(_) {
    console.log('x:', _)
  }
}

// useDefineForClassFields: false
class AssignSemantics extends Base {
  constructor() {
    super()
    this.x = 123
  }
}

// useDefineForClassFields: true
class DefineSemantics extends Base {
  constructor() {
    super()
    Object.defineProperty(this, 'x', { value: 123 })
  }
}

console.log(
  new AssignSemantics().x, // Calls the setter
  new DefineSemantics().x // Doesn't call the setter
)
```
  When you run tsc, the value of useDefineForClassFields defaults to false when it's not specified and the target in tsconfig.json is present but earlier than ES2022. This sort of makes sense because the class field language feature was added in ES2022, so before ES2022 class fields didn't exist (and thus TypeScript's legacy behavior is active). However, TypeScript's target setting currently defaults to ES3 which unfortunately means that the useDefineForClassFields setting currently defaults to false (i.e. to "wrong"). In other words if you run tsc with all default settings, class fields will behave incorrectly.
  
  Previously esbuild tried to do what tsc did. That meant esbuild's version of useDefineForClassFields was false by default, and was also false if esbuild's --target= was present but earlier than es2022. However, TypeScript's legacy class field behavior is becoming increasingly irrelevant and people who expect class fields in TypeScript to work like they do in JavaScript are confused when they use esbuild with default settings. It's also confusing that the behavior of class fields would change if you changed the language target (even though that's exactly how TypeScript works).
  
  So with this release, esbuild will now only use the information in tsconfig.json to determine whether useDefineForClassFields is true or not. Specifically useDefineForClassFields will be respected if present, otherwise it will be false if target is present in tsconfig.json and is ES2021 or earlier, otherwise it will be true. Targets passed to esbuild's --target= setting will no longer affect useDefineForClassFields.
  
  Note that this means different directories in your build can have different values for this setting since esbuild allows different directories to have different tsconfig.json files within the same build. This should let you migrate your code one directory at a time without esbuild's --target= setting affecting the semantics of your code.
- Add support for verbatimModuleSyntax from TypeScript 5.0
  
  TypeScript 5.0 added a new option called verbatimModuleSyntax that deprecates and replaces two older options, preserveValueImports and importsNotUsedAsValues. Setting verbatimModuleSyntax to true in tsconfig.json tells esbuild to not drop unused import statements. Specifically esbuild now treats "verbatimModuleSyntax": true as if you had specified both "preserveValueImports": true and "importsNotUsedAsValues": "preserve".
- Add multiple inheritance for tsconfig.json from TypeScript 5.0
  
  TypeScript 5.0 now allows multiple inheritance for tsconfig.json files. You can now pass an array of filenames via the extends parameter and your tsconfig.json will start off containing properties from all of those configuration files, in order. This release of esbuild adds support for this new TypeScript feature.
- Remove support for moduleSuffixes (#2395)
  
  The community has requested that esbuild remove support for TypeScript's moduleSuffixes feature, so it has been removed in this release. Instead you can use esbuild's --resolve-extensions= feature to select which module suffix you want to build with.
- Apply --tsconfig= overrides to stdin and virtual files (#385, #2543)
  
  When you override esbuild's automatic tsconfig.json file detection with --tsconfig= to pass a specific tsconfig.json file, esbuild previously didn't apply these settings to source code passed via the stdin API option or to TypeScript files from plugins that weren't in the file namespace. This release changes esbuild's behavior so that settings from tsconfig.json also apply to these source code files as well.
- Support --tsconfig-raw= in build API calls (#943, #2440)
  
  Previously if you wanted to override esbuild's automatic tsconfig.json file detection, you had to create a new tsconfig.json file and pass the file name to esbuild via the --tsconfig= flag. With this release, you can now optionally use --tsconfig-raw= instead to pass the contents of tsconfig.json to esbuild directly instead of passing the file name. For example, you can now use --tsconfig-raw={"compilerOptions":{"experimentalDecorators":true}} to enable TypeScript experimental decorators directly using a command-line flag (assuming you escape the quotes correctly using your current shell's quoting rules). The --tsconfig-raw= flag previously only worked with transform API calls but with this release, it now works with build API calls too.
- Ignore all tsconfig.json files in node_modules (#276, #2386)
  
  This changes esbuild's behavior that applies tsconfig.json to all files in the subtree of the directory containing tsconfig.json. In version 0.12.7, esbuild started ignoring tsconfig.json files inside node_modules folders. The rationale is that people typically do this by mistake and that doing this intentionally is a rare use case that doesn't need to be supported. However, this change only applied to certain syntax-specific settings (e.g. jsxFactory) but did not apply to path resolution settings (e.g. paths). With this release, esbuild will now ignore all tsconfig.json files in node_modules instead of only ignoring certain settings.
- Ignore tsconfig.json when resolving paths within node_modules (#2481)
  
  Previously fields in tsconfig.json related to path resolution (e.g. paths) were respected for all files in the subtree containing that tsconfig.json file, even within a nested node_modules subdirectory. This meant that a project's paths settings could potentially affect any bundled packages. With this release, esbuild will no longer use tsconfig.json settings during path resolution inside nested node_modules subdirectories.
- Prefer .js over .ts within node_modules (#3019)
  
  The default list of implicit extensions that esbuild will try appending to import paths contains .ts before .js. This makes it possible to bundle TypeScript projects that reference other files in the project using extension-less imports (e.g. ./some-file to load ./some-file.ts instead of ./some-file.js). However, this behavior is undesirable within node_modules directories. Some package authors publish both their original TypeScript code and their compiled JavaScript code side-by-side. In these cases, esbuild should arguably be using the compiled JavaScript files instead of the original TypeScript files because the TypeScript compilation settings for files within the package should be determined by the package author, not the user of esbuild. So with this release, esbuild will now prefer implicit .js extensions over .ts when searching for import paths within node_modules.
These changes are intended to improve esbuild's compatibility with tsc and reduce the number of unfortunate behaviors regarding tsconfig.json and esbuild.
Add a workaround for bugs in Safari 16.2 and earlier (#3072)

Safari's JavaScript parser had a bug (which has now been fixed) where at least something about unary/binary operators nested inside default arguments nested inside either a function or class expression was incorrectly considered a syntax error if that expression was the target of a property assignment. Here are some examples that trigger this Safari bug:
```
❱ x(function (y = -1) {}.z = 2)
SyntaxError: Left hand side of operator '=' must be a reference.

❱ x(class { f(y = -1) {} }.z = 2)
SyntaxError: Left hand side of operator '=' must be a reference.
```
It's not clear what the exact conditions are that trigger this bug. However, a workaround for this bug appears to be to post-process your JavaScript to wrap any in function and class declarations that are the direct target of a property access expression in parentheses. That's the workaround that UglifyJS applies for this issue: mishoo/UglifyJS#2056. So that's what esbuild now does starting with this release:
```
// Original code
x(function (y = -1) {}.z = 2, class { f(y = -1) {} }.z = 2)

// Old output (with --minify --target=safari16.2)
x(function(c=-1){}.z=2,class{f(c=-1){}}.z=2);

// New output (with --minify --target=safari16.2)
x((function(c=-1){}).z=2,(class{f(c=-1){}}).z=2);
```
This fix is not enabled by default. It's only enabled when --target= contains Safari 16.2 or earlier, such as with --target=safari16.2. You can also explicitly enable or disable this specific transform (called function-or-class-property-access) with --supported:function-or-class-property-access=false.

Fix esbuild's TypeScript type declarations to forbid unknown properties (#3089)

Version 0.17.0 of esbuild introduced a specific form of function overloads in the TypeScript type definitions for esbuild's API calls that looks like this:

interface TransformOptions {
  legalComments?: 'none' | 'inline' | 'eof' | 'external'
}

interface TransformResult<ProvidedOptions extends TransformOptions = TransformOptions> {
  legalComments: string | (ProvidedOptions['legalComments'] extends 'external' ? never : undefined)
}

declare function transformSync<ProvidedOptions extends TransformOptions>(input: string, options?: ProvidedOptions): TransformResult<ProvidedOptions>
declare function transformSync(input: string, options?: TransformOptions): TransformResult

This more accurately reflects how esbuild's JavaScript API behaves. The result object returned by transformSync only has the legalComments property if you pass legalComments: 'external':

// These have type "string | undefined"
transformSync('').legalComments
transformSync('', { legalComments: 'eof' }).legalComments

// This has type "string"
transformSync('', { legalComments: 'external' }).legalComments

However, this form of function overloads unfortunately allows typos (e.g. egalComments) to pass the type checker without generating an error as TypeScript allows all objects with unknown properties to extend TransformOptions. These typos result in esbuild's API throwing an error at run-time.

To prevent typos during type checking, esbuild's TypeScript type definitions will now use a different form that looks like this:

type SameShape<Out, In extends Out> = In & { [Key in Exclude<keyof In, keyof Out>]: never }

interface TransformOptions {
  legalComments?: 'none' | 'inline' | 'eof' | 'external'
}

interface TransformResult<ProvidedOptions extends TransformOptions = TransformOptions> {
  legalComments: string | (ProvidedOptions['legalComments'] extends 'external' ? never : undefined)
}

declare function transformSync<T extends TransformOptions>(input: string, options?: SameShape<TransformOptions, T>): TransformResult<T>

This change should hopefully not affect correct code. It should hopefully introduce type errors only for incorrect code.

Fix CSS nesting transform for pseudo-elements (#3119)

This release fixes esbuild's CSS nesting transform for pseudo-elements (e.g. ::before and ::after). The CSS nesting specification says that the nesting selector does not work with pseudo-elements. This can be seen in the example below: esbuild does not carry the parent pseudo-element ::before through the nesting selector &. However, that doesn't apply to pseudo-elements that are within the same selector. Previously esbuild had a bug where it considered pseudo-elements in both locations as invalid. This release changes esbuild to only consider those from the parent selector invalid, which should align with the specification:
```
/* Original code */
a, b::before {
  &.c, &::after {
    content: 'd';
  }
}

/* Old output (with --target=chrome90) */
a:is(.c, ::after) {
  content: "d";
}

/* New output (with --target=chrome90) */
a.c,
a::after {
  content: "d";
}
```

Forbid & before a type selector in nested CSS

The people behind the work-in-progress CSS nesting specification have very recently decided to forbid nested CSS that looks like &div. You will have to use either div& or &:is(div) instead. This release of esbuild has been updated to take this new change into consideration. Doing this now generates a warning. The suggested fix is slightly different depending on where in the overall selector it happened:

▲ [WARNING] Cannot use type selector "input" directly after nesting selector "&" [css-syntax-error]

    example.css:2:3:
      2 │   &input {
        │    ~~~~~
        ╵    :is(input)

  CSS nesting syntax does not allow the "&" selector to come before a type selector. You can wrap
  this selector in ":is()" as a workaround. This restriction exists to avoid problems with SASS
  nesting, where the same syntax means something very different that has no equivalent in real CSS
  (appending a suffix to the parent selector).

▲ [WARNING] Cannot use type selector "input" directly after nesting selector "&" [css-syntax-error]

    example.css:6:8:
      6 │   .form &input {
        │         ~~~~~~
        ╵         input&

  CSS nesting syntax does not allow the "&" selector to come before a type selector. You can move
  the "&" to the end of this selector as a workaround. This restriction exists to avoid problems
  with SASS nesting, where the same syntax means something very different that has no equivalent in
  real CSS (appending a suffix to the parent selector).

0.17.19

Fix CSS transform bugs with nested selectors that start with a combinator (#3096)

This release fixes several bugs regarding transforming nested CSS into non-nested CSS for older browsers. The bugs were due to lack of test coverage for nested selectors with more than one compound selector where they all start with the same combinator. Here's what some problematic cases look like before and after these fixes:

/* Original code */
.foo {
  > &a,
  > &b {
    color: red;
  }
}
.bar {
  > &a,
  + &b {
    color: green;
  }
}

/* Old output (with --target=chrome90) */
.foo :is(> .fooa, > .foob) {
  color: red;
}
.bar :is(> .bara, + .barb) {
  color: green;
}

/* New output (with --target=chrome90) */
.foo > :is(a.foo, b.foo) {
  color: red;
}
.bar > a.bar,
.bar + b.bar {
  color: green;
}

Fix bug with TypeScript parsing of instantiation expressions followed by = (#3111)

This release fixes esbuild's TypeScript-to-JavaScript conversion code in the case where a potential instantiation expression is followed immediately by a = token (such that the trailing > becomes a >= token). Previously esbuild considered that to still be an instantiation expression, but the official TypeScript compiler considered it to be a >= operator instead. This release changes esbuild's interpretation to match TypeScript. This edge case currently appears to be problematic for other TypeScript-to-JavaScript converters as well:

Original code TypeScript esbuild 0.17.18 esbuild 0.17.19 Sucrase Babel

x<y>=a<b<c>>() x<y>=a(); x=a(); x<y>=a(); x=a() Invalid left-hand side in assignment expression
Avoid removing unrecognized directives from the directive prologue when minifying (#3115)

The directive prologue in JavaScript is a sequence of top-level string expressions that come before your code. The only directives that JavaScript engines currently recognize are use strict and sometimes use asm. However, the people behind React have made up their own directive for their own custom dialect of JavaScript. Previously esbuild only preserved the use strict directive when minifying, although you could still write React JavaScript with esbuild using something like --banner:js="'your directive here';". With this release, you can now put arbitrary directives in the entry point and esbuild will preserve them in its minified output:
```
// Original code
'use wtf'; console.log(123)

// Old output (with --minify)
console.log(123);

// New output (with --minify)
"use wtf";console.log(123);
```
Note that this means esbuild will no longer remove certain stray top-level strings when minifying. This behavior is an intentional change because these stray top-level strings are actually part of the directive prologue, and could potentially have semantics assigned to them (as was the case with React).

Improved minification of binary shift operators

With this release, esbuild's minifier will now evaluate the << and >>> operators if the resulting code would be shorter:

// Original code
console.log(10 << 10, 10 << 20, -123 >>> 5, -123 >>> 10);

// Old output (with --minify)
console.log(10<<10,10<<20,-123>>>5,-123>>>10);

// New output (with --minify)
console.log(10240,10<<20,-123>>>5,4194303);

0.17.18

Fix non-default JSON import error with export {} from (#3070)

This release fixes a bug where esbuild incorrectly identified statements of the form export { default as x } from "y" assert { type: "json" } as a non-default import. The bug did not affect code of the form import { default as x } from ... (only code that used the export keyword).
Fix a crash with an invalid subpath import (#3067)

Previously esbuild could crash when attempting to generate a friendly error message for an invalid subpath import (i.e. an import starting with #). This happened because esbuild originally only supported the exports field and the code for that error message was not updated when esbuild later added support for the imports field. This crash has been fixed.

0.17.17

Fix CSS nesting transform for top-level & (#3052)

Previously esbuild could crash with a stack overflow when lowering CSS nesting rules with a top-level &, such as in the code below. This happened because esbuild's CSS nesting transform didn't handle top-level &, causing esbuild to inline the top-level selector into itself. This release handles top-level & by replacing it with the :scope pseudo-class:
```
/* Original code */
&,
a {
  .b {
    color: red;
  }
}

/* New output (with --target=chrome90) */
:is(:scope, a) .b {
  color: red;
}
```
Support exports in package.json for extends in tsconfig.json (#3058)

TypeScript 5.0 added the ability to use extends in tsconfig.json to reference a path in a package whose package.json file contains an exports map that points to the correct location. This doesn't automatically work in esbuild because tsconfig.json affects esbuild's path resolution, so esbuild's normal path resolution logic doesn't apply.

This release adds support for doing this by adding some additional code that attempts to resolve the extends path using the exports field. The behavior should be similar enough to esbuild's main path resolution logic to work as expected.

Note that esbuild always treats this extends import as a require() import since that's what TypeScript appears to do. Specifically the require condition will be active and the import condition will be inactive.
Fix watch mode with NODE_PATH (#3062)

Node has a rarely-used feature where you can extend the set of directories that node searches for packages using the NODE_PATH environment variable. While esbuild supports this too, previously a bug prevented esbuild's watch mode from picking up changes to imported files that were contained directly in a NODE_PATH directory. You're supposed to use NODE_PATH for packages, but some people abuse this feature by putting files in that directory instead (e.g. node_modules/some-file.js instead of node_modules/some-pkg/some-file.js). The watch mode bug happens when you do this because esbuild first tries to read some-file.js as a directory and then as a file. Watch mode was incorrectly waiting for some-file.js to become a valid directory. This release fixes this edge case bug by changing watch mode to watch some-file.js as a file when this happens.

0.17.16

Fix CSS nesting transform for triple-nested rules that start with a combinator (#3046)

This release fixes a bug with esbuild where triple-nested CSS rules that start with a combinator were not transformed correctly for older browsers. Here's an example of such a case before and after this bug fix:

/* Original input */
.a {
  color: red;
  > .b {
    color: green;
    > .c {
      color: blue;
    }
  }
}

/* Old output (with --target=chrome90) */
.a {
  color: red;
}
.a > .b {
  color: green;
}
.a .b > .c {
  color: blue;
}

/* New output (with --target=chrome90) */
.a {
  color: red;
}
.a > .b {
  color: green;
}
.a > .b > .c {
  color: blue;
}

Support --inject with a file loaded using the copy loader (#3041)

This release now allows you to use --inject with a file that is loaded using the copy loader. The copy loader copies the imported file to the output directory verbatim and rewrites the path in the import statement to point to the copied output file. When used with --inject, this means the injected file will be copied to the output directory as-is and a bare import statement for that file will be inserted in any non-copy output files that esbuild generates.

Note that since esbuild doesn't parse the contents of copied files, esbuild will not expose any of the export names as usable imports when you do this (in the way that esbuild's --inject feature is typically used). However, any side-effects that the injected file has will still occur.

0.17.15

Allow keywords as type parameter names in mapped types (#3033)

TypeScript allows type keywords to be used as parameter names in mapped types. Previously esbuild incorrectly treated this as an error. Code that does this is now supported:
```
type Foo = 'a' | 'b' | 'c'
type A = { [keyof in Foo]: number }
type B = { [infer in Foo]: number }
type C = { [readonly in Foo]: number }
```
Add annotations for re-exported modules in node (#2486, #3029)

Node lets you import named imports from a CommonJS module using ESM import syntax. However, the allowed names aren't derived from the properties of the CommonJS module. Instead they are derived from an arbitrary syntax-only analysis of the CommonJS module's JavaScript AST.

To accommodate node doing this, esbuild's ESM-to-CommonJS conversion adds a special non-executable "annotation" for node that describes the exports that node should expose in this scenario. It takes the form 0 && (module.exports = { ... }) and comes at the end of the file (0 && expr means expr is never evaluated).

Previously esbuild didn't do this for modules re-exported using the export * from syntax. Annotations for these re-exports will now be added starting with this release:
```
// Original input
export { foo } from './foo'
export * from './bar'

// Old output (with --format=cjs --platform=node)
...
0 && (module.exports = {
  foo
});

// New output (with --format=cjs --platform=node)
...
0 && (module.exports = {
  foo,
  ...require("./bar")
});
```
Note that you need to specify both --format=cjs and --platform=node to get these node-specific annotations.
Avoid printing an unnecessary space in between a number and a . (#3026)

JavaScript typically requires a space in between a number token and a . token to avoid the . being interpreted as a decimal point instead of a member expression. However, this space is not required if the number token itself contains a decimal point, an exponent, or uses a base other than 10. This release of esbuild now avoids printing the unnecessary space in these cases:
```
// Original input
foo(1000 .x, 0 .x, 0.1 .x, 0.0001 .x, 0xFFFF_0000_FFFF_0000 .x)

// Old output (with --minify)
foo(1e3 .x,0 .x,.1 .x,1e-4 .x,0xffff0000ffff0000 .x);

// New output (with --minify)
foo(1e3.x,0 .x,.1.x,1e-4.x,0xffff0000ffff0000.x);
```
Fix server-sent events with live reload when writing to the file system root (#3027)

This release fixes a bug where esbuild previously failed to emit server-sent events for live reload when outdir was the file system root, such as /. This happened because / is the only path on Unix that cannot have a trailing slash trimmed from it, which was fixed by improved path handling.

0.17.14

Allow the TypeScript 5.0 const modifier in object type declarations (#3021)

The new TypeScript 5.0 const modifier was added to esbuild in version 0.17.5, and works with classes, functions, and arrow expressions. However, support for it wasn't added to object type declarations (e.g. interfaces) due to an oversight. This release adds support for these cases, so the following TypeScript 5.0 code can now be built with esbuild:
```
interface Foo { <const T>(): T }
type Bar = { new <const T>(): T }
```
Implement preliminary lowering for CSS nesting (#1945)

Chrome has implemented the new CSS nesting specification in version 112, which is currently in beta but will become stable very soon. So CSS nesting is now a part of the web platform!

This release of esbuild can now transform nested CSS syntax into non-nested CSS syntax for older browsers. The transformation relies on the :is() pseudo-class in many cases, so the transformation is only guaranteed to work when targeting browsers that support :is() (e.g. Chrome 88+). You'll need to set esbuild's target to the browsers you intend to support to tell esbuild to do this transformation. You will get a warning if you use CSS nesting syntax with a target which includes older browsers that don't support :is().

The lowering transformation looks like this:
```
/* Original input */
a.btn {
  color: #333;
  &:hover { color: #444 }
  &:active { color: #555 }
}

/* New output (with --target=chrome88) */
a.btn {
  color: #333;
}
a.btn:hover {
  color: #444;
}
a.btn:active {
  color: #555;
}
```
More complex cases may generate the :is() pseudo-class:
```
/* Original input */
div, p {
  .warning, .error {
    padding: 20px;
  }
}

/* New output (with --target=chrome88) */
:is(div, p) :is(.warning, .error) {
  padding: 20px;
}
```
In addition, esbuild now has a special warning message for nested style rules that start with an identifier. This isn't allowed in CSS because the syntax would be ambiguous with the existing declaration syntax. The new warning message looks like this:
```
▲ [WARNING] A nested style rule cannot start with "p" because it looks like the start of a declaration [css-syntax-error]

    <stdin>:1:7:
      1 │ main { p { margin: auto } }
        │        ^
        ╵        :is(p)

  To start a nested style rule with an identifier, you need to wrap the identifier in ":is(...)" to
  prevent the rule from being parsed as a declaration.
```
Keep in mind that the transformation in this release is a preliminary implementation. CSS has many features that interact in complex ways, and there may be some edge cases that don't work correctly yet.

Minification now removes unnecessary & CSS nesting selectors

This release introduces the following CSS minification optimizations:

/* Original input */
a {
  font-weight: bold;
  & {
    color: blue;
  }
  & :hover {
    text-decoration: underline;
  }
}

/* Old output (with --minify) */
a{font-weight:700;&{color:#00f}& :hover{text-decoration:underline}}

/* New output (with --minify) */
a{font-weight:700;:hover{text-decoration:underline}color:#00f}

Minification now removes duplicates from CSS selector lists

This release introduces the following CSS minification optimization:

/* Original input */
div, div { color: red }

/* Old output (with --minify) */
div,div{color:red}

/* New output (with --minify) */
div{color:red}

0.17.13

Work around an issue with NODE_PATH and Go's WebAssembly internals (#3001)

Go's WebAssembly implementation returns EINVAL instead of ENOTDIR when using the readdir syscall on a file. This messes up esbuild's implementation of node's module resolution algorithm since encountering ENOTDIR causes esbuild to continue its search (since it's a normal condition) while other encountering other errors causes esbuild to fail with an I/O error (since it's an unexpected condition). You can encounter this issue in practice if you use node's legacy NODE_PATH feature to tell esbuild to resolve node modules in a custom directory that was not installed by npm. This release works around this problem by converting EINVAL into ENOTDIR for the readdir syscall.
Fix a minification bug with CSS @layer rules that have parsing errors (#3016)

CSS at-rules require either a {} block or a semicolon at the end. Omitting both of these causes esbuild to treat the rule as an unknown at-rule. Previous releases of esbuild had a bug that incorrectly removed unknown at-rules without any children during minification if the at-rule token matched an at-rule that esbuild can handle. Specifically cssnano can generate @layer rules with parsing errors, and empty @layer rules cannot be removed because they have side effects (@layer didn't exist when esbuild's CSS support was added, so esbuild wasn't written to handle this). This release changes esbuild to no longer discard @layer rules with parsing errors when minifying (the rule @layer c has a parsing error):
```
/* Original input */
@layer a {
  @layer b {
    @layer c
  }
}

/* Old output (with --minify) */
@layer a.b;

/* New output (with --minify) */
@layer a.b.c;
```
Unterminated strings in CSS are no longer an error

The CSS specification provides rules for handling parsing errors. One of those rules is that user agents must close strings upon reaching the end of a line (i.e., before an unescaped line feed, carriage return or form feed character), but then drop the construct (declaration or rule) in which the string was found. For example:
```
p {
  color: green;
  font-family: 'Courier New Times
  color: red;
  color: green;
}
```
...would be treated the same as:
```
p { color: green; color: green; }
```
...because the second declaration (from font-family to the semicolon after color: red) is invalid and is dropped.

Previously using this CSS with esbuild failed to build due to a syntax error, even though the code can be interpreted by a browser. With this release, the code now produces a warning instead of an error, and esbuild prints the invalid CSS such that it stays invalid in the output:
```
/* esbuild's new non-minified output: */
p {
  color: green;
  font-family: 'Courier New Times
  color: red;
  color: green;
}
```
```
/* esbuild's new minified output: */
p{font-family:'Courier New Times
color: red;color:green}
```

0.17.12

Fix a crash when parsing inline TypeScript decorators (#2991)

Previously esbuild's TypeScript parser crashed when parsing TypeScript decorators if the definition of the decorator was inlined into the decorator itself:
```
@(function sealed(constructor: Function) {
  Object.seal(constructor);
  Object.seal(constructor.prototype);
})
class Foo {}
```
This crash was not noticed earlier because this edge case did not have test coverage. The crash is fixed in this release.

0.17.11

Fix the alias feature to always prefer the longest match (#2963)

It's possible to configure conflicting aliases such as --alias:a=b and --alias:a/c=d, which is ambiguous for the import path a/c/x (since it could map to either b/c/x or d/x). Previously esbuild would pick the first matching alias, which would non-deterministically pick between one of the possible matches. This release fixes esbuild to always deterministically pick the longest possible match.

Minify calls to some global primitive constructors (#2962)

With this release, esbuild's minifier now replaces calls to Boolean/Number/String/BigInt with equivalent shorter code when relevant:

// Original code
console.log(
  Boolean(a ? (b | c) !== 0 : (c & d) !== 0),
  Number(e ? '1' : '2'),
  String(e ? '1' : '2'),
  BigInt(e ? 1n : 2n),
)

// Old output (with --minify)
console.log(Boolean(a?(b|c)!==0:(c&d)!==0),Number(e?"1":"2"),String(e?"1":"2"),BigInt(e?1n:2n));

// New output (with --minify)
console.log(!!(a?b|c:c&d),+(e?"1":"2"),e?"1":"2",e?1n:2n);

Adjust some feature compatibility tables for node (#2940)

This release makes the following adjustments to esbuild's internal feature compatibility tables for node, which tell esbuild which versions of node are known to support all aspects of that feature:
- class-private-brand-checks: node v16.9+ => node v16.4+ (a decrease)
- hashbang: node v12.0+ => node v12.5+ (an increase)
- optional-chain: node v16.9+ => node v16.1+ (a decrease)
- template-literal: node v4+ => node v10+ (an increase)
Each of these adjustments was identified by comparing against data from the node-compat-table package and was manually verified using old node executables downloaded from https://nodejs.org/download/release/.

0.17.10

Update esbuild's handling of CSS nesting to match the latest specification changes (#1945)

The syntax for the upcoming CSS nesting feature has recently changed. The @nest prefix that was previously required in some cases is now gone, and nested rules no longer have to start with & (as long as they don't start with an identifier or function token).

This release updates esbuild's pass-through handling of CSS nesting syntax to match the latest specification changes. So you can now use esbuild to bundle CSS containing nested rules and try them out in a browser that supports CSS nesting (which includes nightly builds of both Chrome and Safari).

However, I'm not implementing lowering of nested CSS to non-nested CSS for older browsers yet. While the syntax has been decided, the semantics are still in flux. In particular, there is still some debate about changing the fundamental way that CSS nesting works. For example, you might think that the following CSS is equivalent to a .outer .inner button { ... } rule:
```
.inner button {
  .outer & {
    color: red;
  }
}
```
But instead it's actually equivalent to a .outer :is(.inner button) { ... } rule which unintuitively also matches the following DOM structure:
```
<div class="inner">
  <div class="outer">
    <button></button>
  </div>
</div>
```
The :is() behavior is preferred by browser implementers because it's more memory-efficient, but the straightforward translation into a .outer .inner button { ... } rule is preferred by developers used to the existing CSS preprocessing ecosystem (e.g. SASS). It seems premature to commit esbuild to specific semantics for this syntax at this time given the ongoing debate.

Fix cross-file CSS rule deduplication involving url() tokens (#2936)

Previously cross-file CSS rule deduplication didn't handle url() tokens correctly. These tokens contain references to import paths which may be internal (i.e. in the bundle) or external (i.e. not in the bundle). When comparing two url() tokens for equality, the underlying import paths should be compared instead of their references. This release of esbuild fixes url() token comparisons. One side effect is that @font-face rules should now be deduplicated correctly across files:

/* Original code */
@import "data:text/css, \
  @import 'http://example.com/style.css'; \
  @font-face { src: url(http://example.com/font.ttf) }";
@import "data:text/css, \
  @font-face { src: url(http://example.com/font.ttf) }";

/* Old output (with --bundle --minify) */
@import"http://example.com/style.css";@font-face{src:url(http://example.com/font.ttf)}@font-face{src:url(http://example.com/font.ttf)}

/* New output (with --bundle --minify) */
@import"http://example.com/style.css";@font-face{src:url(http://example.com/font.ttf)}

0.17.9

Parse rest bindings in TypeScript types (#2937)

Previously esbuild was unable to parse the following valid TypeScript code:
```
let tuple: (...[e1, e2, ...es]: any) => any
```
This release includes support for parsing code like this.

Fix TypeScript code translation for certain computed declare class fields (#2914)

In TypeScript, the key of a computed declare class field should only be preserved if there are no decorators for that field. Previously esbuild always preserved the key, but esbuild will now remove the key to match the output of the TypeScript compiler:

// Original code
declare function dec(a: any, b: any): any
declare const removeMe: unique symbol
declare const keepMe: unique symbol
class X {
    declare [removeMe]: any
    @dec declare [keepMe]: any
}

// Old output
var _a;
class X {
}
removeMe, _a = keepMe;
__decorateClass([
  dec
], X.prototype, _a, 2);

// New output
var _a;
class X {
}
_a = keepMe;
__decorateClass([
  dec
], X.prototype, _a, 2);

Fix a crash with path resolution error generation (#2913)

In certain situations, a module containing an invalid import path could previously cause esbuild to crash when it attempts to generate a more helpful error message. This crash has been fixed.

0.17.8

Fix a minification bug with non-ASCII identifiers (#2910)

This release fixes a bug with esbuild where non-ASCII identifiers followed by a keyword were incorrectly not separated by a space. This bug affected both the in and instanceof keywords. Here's an example of the fix:
```
// Original code
π in a

// Old output (with --minify --charset=utf8)
πin a;

// New output (with --minify --charset=utf8)
π in a;
```
Fix a regression with esbuild's WebAssembly API in version 0.17.6 (#2911)

Version 0.17.6 of esbuild updated the Go toolchain to version 1.20.0. This had the unfortunate side effect of increasing the amount of stack space that esbuild uses (presumably due to some changes to Go's WebAssembly implementation) which could cause esbuild's WebAssembly-based API to crash with a stack overflow in cases where it previously didn't crash. One such case is the package grapheme-splitter which contains code that looks like this:
```
if (
  (0x0300 <= code && code <= 0x036F) ||
  (0x0483 <= code && code <= 0x0487) ||
  (0x0488 <= code && code <= 0x0489) ||
  (0x0591 <= code && code <= 0x05BD) ||
  // ... many hundreds of lines later ...
) {
  return;
}
```
This edge case involves a chain of binary operators that results in an AST over 400 nodes deep. Normally this wouldn't be a problem because Go has growable call stacks, so the call stack would just grow to be as large as needed. However, WebAssembly byte code deliberately doesn't expose the ability to manipulate the stack pointer, so Go's WebAssembly translation is forced to use the fixed-size WebAssembly call stack. So esbuild's WebAssembly implementation is vulnerable to stack overflow in cases like these.

It's not unreasonable for this to cause a stack overflow, and for esbuild's answer to this problem to be "don't write code like this." That's how many other AST-manipulation tools handle this problem. However, it's possible to implement AST traversal using iteration instead of recursion to work around limited call stack space. This version of esbuild implements this code transformation for esbuild's JavaScript parser and printer, so esbuild's WebAssembly implementation is now able to process the grapheme-splitter package (at least when compiled with Go 1.20.0 and run with node's WebAssembly implementation).

0.17.7

Change esbuild's parsing of TypeScript instantiation expressions to match TypeScript 4.8+ (#2907)

This release updates esbuild's implementation of instantiation expression erasure to match microsoft/TypeScript#49353. The new rules are as follows (copied from TypeScript's PR description):
When a potential type argument list is followed by
- a line break,
- an ( token,
- a template literal string, or
- any token except < or > that isn't the start of an expression,
we consider that construct to be a type argument list. Otherwise we consider the construct to be a < relational expression followed by a > relational expression.
Ignore sideEffects: false for imported CSS files (#1370, #1458, #2905)

This release ignores the sideEffects annotation in package.json for CSS files that are imported into JS files using esbuild's css loader. This means that these CSS files are no longer be tree-shaken.

Importing CSS into JS causes esbuild to automatically create a CSS entry point next to the JS entry point containing the bundled CSS. Previously packages that specified some form of "sideEffects": false could potentially cause esbuild to consider one or more of the JS files on the import path to the CSS file to be side-effect free, which would result in esbuild removing that CSS file from the bundle. This was problematic because the removal of that CSS is outwardly observable, since all CSS is global, so it was incorrect for previous versions of esbuild to tree-shake CSS files imported into JS files.

Add constant folding for certain additional equality cases (#2394, #2895)

This release adds constant folding for expressions similar to the following:

// Original input
console.log(
  null === 'foo',
  null === undefined,
  null == undefined,
  false === 0,
  false == 0,
  1 === true,
  1 == true,
)

// Old output
console.log(
  null === "foo",
  null === void 0,
  null == void 0,
  false === 0,
  false == 0,
  1 === true,
  1 == true
);

// New output
console.log(
  false,
  false,
  true,
  false,
  true,
  false,
  true
);

0.17.6

Fix a CSS parser crash on invalid CSS (#2892)

Previously the following invalid CSS caused esbuild's parser to crash:
```
@media screen
```
The crash was caused by trying to construct a helpful error message assuming that there was an opening { token, which is not the case here. This release fixes the crash.
Inline TypeScript enums that are referenced before their declaration

Previously esbuild inlined enums within a TypeScript file from top to bottom, which meant that references to TypeScript enum members were only inlined within the same file if they came after the enum declaration. With this release, esbuild will now inline enums even when they are referenced before they are declared:
```
// Original input
export const foo = () => Foo.FOO
const enum Foo { FOO = 0 }

// Old output (with --tree-shaking=true)
export const foo = () => Foo.FOO;
var Foo = /* @__PURE__ */ ((Foo2) => {
  Foo2[Foo2["FOO"] = 0] = "FOO";
  return Foo2;
})(Foo || {});

// New output (with --tree-shaking=true)
export const foo = () => 0 /* FOO */;
```
This makes esbuild's TypeScript output smaller and faster when processing code that does this. I noticed this issue when I ran the TypeScript compiler's source code through esbuild's bundler. Now that the TypeScript compiler is going to be bundled with esbuild in the upcoming TypeScript 5.0 release, improvements like this will also improve the TypeScript compiler itself!
Fix esbuild installation on Arch Linux (#2785, #2812, #2865)

Someone made an unofficial esbuild package for Linux that adds the ESBUILD_BINARY_PATH=/usr/bin/esbuild environment variable to the user's default environment. This breaks all npm installations of esbuild for users with this unofficial Linux package installed, which has affected many people. Most (all?) people who encounter this problem haven't even installed this unofficial package themselves; instead it was installed for them as a dependency of another Linux package. The problematic change to add the ESBUILD_BINARY_PATH environment variable was reverted in the latest version of this unofficial package. However, old versions of this unofficial package are still there and will be around forever. With this release, ESBUILD_BINARY_PATH is now ignored by esbuild's install script when it's set to the value /usr/bin/esbuild. This should unbreak using npm to install esbuild in these problematic Linux environments.

Note: The ESBUILD_BINARY_PATH variable is an undocumented way to override the location of esbuild's binary when esbuild's npm package is installed, which is necessary to substitute your own locally-built esbuild binary when debugging esbuild's npm package. It's only meant for very custom situations and should absolutely not be forced on others by default, especially without their knowledge. I may remove the code in esbuild's installer that reads ESBUILD_BINARY_PATH in the future to prevent these kinds of issues. It will unfortunately make debugging esbuild harder. If ESBUILD_BINARY_PATH is ever removed, it will be done in a "breaking change" release.

0.17.5

Parse const type parameters from TypeScript 5.0

The TypeScript 5.0 beta announcement adds const type parameters to the language. You can now add the const modifier on a type parameter of a function, method, or class like this:
```
type HasNames = { names: readonly string[] };
const getNamesExactly = <const T extends HasNames>(arg: T): T["names"] => arg.names;
const names = getNamesExactly({ names: ["Alice", "Bob", "Eve"] });
```
The type of names in the above example is readonly ["Alice", "Bob", "Eve"]. Marking the type parameter as const behaves as if you had written as const at every use instead. The above code is equivalent to the following TypeScript, which was the only option before TypeScript 5.0:
```
type HasNames = { names: readonly string[] };
const getNamesExactly = <T extends HasNames>(arg: T): T["names"] => arg.names;
const names = getNamesExactly({ names: ["Alice", "Bob", "Eve"] } as const);
```
You can read the announcement for more information.
Make parsing generic async arrow functions more strict in .tsx files

Previously esbuild's TypeScript parser incorrectly accepted the following code as valid:
```
let fn = async <T> () => {};
```
The official TypeScript parser rejects this code because it thinks it's the identifier async followed by a JSX element starting with <T>. So with this release, esbuild will now reject this syntax in .tsx files too. You'll now have to add a comma after the type parameter to get generic arrow functions like this to parse in .tsx files:
```
let fn = async <T,> () => {};
```
Allow the in and out type parameter modifiers on class expressions

TypeScript 4.7 added the in and out modifiers on the type parameters of classes, interfaces, and type aliases. However, while TypeScript supported them on both class expressions and class statements, previously esbuild only supported them on class statements due to an oversight. This release now allows these modifiers on class expressions too:
```
declare let Foo: any;
Foo = class <in T> { };
Foo = class <out T> { };
```
Update enum constant folding for TypeScript 5.0

TypeScript 5.0 contains an updated definition of what it considers a constant expression:
An expression is considered a constant expression if it is
- a number or string literal,
- a unary +, -, or ~ applied to a numeric constant expression,
- a binary +, -, *, /, %, **, <<, >>, >>>, |, &, ^ applied to two numeric constant expressions,
- a binary + applied to two constant expressions whereof at least one is a string,
- a template expression where each substitution expression is a constant expression,
- a parenthesized constant expression,
- a dotted name (e.g. x.y.z) that references a const variable with a constant expression initializer and no type annotation,
- a dotted name that references an enum member with an enum literal type, or
- a dotted name indexed by a string literal (e.g. x.y["z"]) that references an enum member with an enum literal type.
This impacts esbuild's implementation of TypeScript's const enum feature. With this release, esbuild will now attempt to follow these new rules. For example, you can now initialize an enum member with a template literal expression that contains a numeric constant:
```
// Original input
const enum Example {
  COUNT = 100,
  ERROR = `Expected ${COUNT} items`,
}
console.log(
  Example.COUNT,
  Example.ERROR,
)

// Old output (with --tree-shaking=true)
var Example = /* @__PURE__ */ ((Example2) => {
  Example2[Example2["COUNT"] = 100] = "COUNT";
  Example2[Example2["ERROR"] = `Expected ${100 /* COUNT */} items`] = "ERROR";
  return Example2;
})(Example || {});
console.log(
  100 /* COUNT */,
  Example.ERROR
);

// New output (with --tree-shaking=true)
console.log(
  100 /* COUNT */,
  "Expected 100 items" /* ERROR */
);
```
These rules are not followed exactly due to esbuild's limitations. The rule about dotted references to const variables is not followed both because esbuild's enum processing is done in an isolated module setting and because doing so would potentially require esbuild to use a type system, which it doesn't have. For example:
```
// The TypeScript compiler inlines this but esbuild doesn't:
declare const x = 'foo'
const enum Foo { X = x }
console.log(Foo.X)
```
Also, the rule that requires converting numbers to a string currently only followed for 32-bit signed integers and non-finite numbers. This is done to avoid accidentally introducing a bug if esbuild's number-to-string operation doesn't exactly match the behavior of a real JavaScript VM. Currently esbuild's number-to-string constant folding is conservative for safety.
Forbid definite assignment assertion operators on class methods

In TypeScript, class methods can use the ? optional property operator but not the ! definite assignment assertion operator (while class fields can use both):
```
class Foo {
  // These are valid TypeScript
  a?
  b!
  x?() {}

  // This is invalid TypeScript
  y!() {}
}
```
Previously esbuild incorrectly allowed the definite assignment assertion operator with class methods. This will no longer be allowed starting with this release.

0.17.4

Implement HTTP HEAD requests in serve mode (#2851)

Previously esbuild's serve mode only responded to HTTP GET requests. With this release, esbuild's serve mode will also respond to HTTP HEAD requests, which are just like HTTP GET requests except that the body of the response is omitted.
Permit top-level await in dead code branches (#2853)

Adding top-level await to a file has a few consequences with esbuild:
1. It causes esbuild to assume that the input module format is ESM, since top-level await is only syntactically valid in ESM. That prevents you from using module and exports for exports and also enables strict mode, which disables certain syntax and changes how function hoisting works (among other things).
2. This will cause esbuild to fail the build if either top-level await isn't supported by your language target (e.g. it's not supported in ES2021) or if top-level await isn't supported by the chosen output format (e.g. it's not supported with CommonJS).
3. Doing this will prevent you from using require() on this file or on any file that imports this file (even indirectly), since the require() function doesn't return a promise and so can't represent top-level await.
This release relaxes these rules slightly: rules 2 and 3 will now no longer apply when esbuild has identified the code branch as dead code, such as when it's behind an if (false) check. This should make it possible to use esbuild to convert code into different output formats that only uses top-level await conditionally. This release does not relax rule 1. Top-level await will still cause esbuild to unconditionally consider the input module format to be ESM, even when the top-level await is in a dead code branch. This is necessary because whether the input format is ESM or not affects the whole file, not just the dead code branch.
Fix entry points where the entire file name is the extension (#2861)

Previously if you passed esbuild an entry point where the file extension is the entire file name, esbuild would use the parent directory name to derive the name of the output file. For example, if you passed esbuild a file ./src/.ts then the output name would be src.js. This bug happened because esbuild first strips the file extension to get ./src/ and then joins the path with the working directory to get the absolute path (e.g. join("/working/dir", "./src/") gives /working/dir/src). However, the join operation also canonicalizes the path which strips the trailing /. Later esbuild uses the "base name" operation to extract the name of the output file. Since there is no trailing /, esbuild returns "src" as the base name instead of "", which causes esbuild to incorrectly include the directory name in the output file name. This release fixes this bug by deferring the stripping of the file extension until after all path manipulations have been completed. So now the file ./src/.ts will generate an output file named .js.
Support replacing property access expressions with inject

At a high level, this change means the inject feature can now replace all of the same kinds of names as the define feature. So inject is basically now a more powerful version of define, instead of previously only being able to do some of the things that define could do.

Soem background is necessary to understand this change if you aren't already familiar with the inject feature. The inject feature lets you replace references to global variable with a shim. It works like this:
1. Put the shim in its own file
2. Export the shim as the name of the global variable you intend to replace
3. Pass the file to esbuild using the inject feature
For example, if you inject the following file using --inject:./injected.js:
```
// injected.js
let processShim = { cwd: () => '/' }
export { processShim as process }
```
Then esbuild will replace all references to process with the processShim variable, which will cause process.cwd() to return '/'. This feature is sort of abusing the ESM export alias syntax to specify the mapping of global variables to shims. But esbuild works this way because using this syntax for that purpose is convenient and terse.

However, if you wanted to replace a property access expression, the process was more complicated and not as nice. You would have to:
1. Put the shim in its own file
2. Export the shim as some random name
3. Pass the file to esbuild using the inject feature
4. Use esbuild's define feature to map the property access expression to the random name you made in step 2
For example, if you inject the following file using --inject:./injected2.js --define:process.cwd=someRandomName:
```
// injected2.js
let cwdShim = () => '/'
export { cwdShim as someRandomName }
```
Then esbuild will replace all references to process.cwd with the cwdShim variable, which will also cause process.cwd() to return '/' (but which this time will not mess with other references to process, which might be desirable).

With this release, using the inject feature to replace a property access expression is now as simple as using it to replace an identifier. You can now use JavaScript's "arbitrary module namespace identifier names" feature to specify the property access expression directly using a string literal. For example, if you inject the following file using --inject:./injected3.js:
```
// injected3.js
let cwdShim = () => '/'
export { cwdShim as 'process.cwd' }
```
Then esbuild will now replace all references to process.cwd with the cwdShim variable, which will also cause process.cwd() to return '/' (but which will also not mess with other references to process).

In addition to inserting a shim for a global variable that doesn't exist, another use case is replacing references to static methods on global objects with cached versions to both minify them better and to make access to them potentially faster. For example:
```
// Injected file
let cachedMin = Math.min
let cachedMax = Math.max
export {
  cachedMin as 'Math.min',
  cachedMax as 'Math.max',
}

// Original input
function clampRGB(r, g, b) {
  return {
    r: Math.max(0, Math.min(1, r)),
    g: Math.max(0, Math.min(1, g)),
    b: Math.max(0, Math.min(1, b)),
  }
}

// Old output (with --minify)
function clampRGB(a,t,m){return{r:Math.max(0,Math.min(1,a)),g:Math.max(0,Math.min(1,t)),b:Math.max(0,Math.min(1,m))}}

// New output (with --minify)
var a=Math.min,t=Math.max;function clampRGB(h,M,m){return{r:t(0,a(1,h)),g:t(0,a(1,M)),b:t(0,a(1,m))}}
```

0.17.3

Fix incorrect CSS minification for certain rules (#2838)

Certain rules such as @media could previously be minified incorrectly. Due to a typo in the duplicate rule checker, two known @-rules that share the same hash code were incorrectly considered to be equal. This problem was made worse by the rule hashing code considering two unknown declarations (such as CSS variables) to have the same hash code, which also isn't optimal from a performance perspective. Both of these issues have been fixed:
```
/* Original input */
@media (prefers-color-scheme: dark) { body { --VAR-1: #000; } }
@media (prefers-color-scheme: dark) { body { --VAR-2: #000; } }

/* Old output (with --minify) */
@media (prefers-color-scheme: dark){body{--VAR-2: #000}}

/* New output (with --minify) */
@media (prefers-color-scheme: dark){body{--VAR-1: #000}}@media (prefers-color-scheme: dark){body{--VAR-2: #000}}
```

0.17.2

Add onDispose to the plugin API (#2140, #2205)

If your plugin wants to perform some cleanup after it's no longer going to be used, you can now use the onDispose API to register a callback for cleanup-related tasks. For example, if a plugin starts a long-running child process then it may want to terminate that process when the plugin is discarded. Previously there was no way to do this. Here's an example:
```
let examplePlugin = {
  name: 'example',
  setup(build) {
    build.onDispose(() => {
      console.log('This plugin is no longer used')
    })
  },
}
```
These onDispose callbacks will be called after every build() call regardless of whether the build failed or not as well as after the first dispose() call on a given build context.

0.17.1

Make it possible to cancel a build (#2725)

The context object introduced in version 0.17.0 has a new cancel() method. You can use it to cancel a long-running build so that you can start a new one without needing to wait for the previous one to finish. When this happens, the previous build should always have at least one error and have no output files (i.e. it will be a failed build).

Using it might look something like this:
- JS:
```
let ctx = await esbuild.context({
  // ...
})

let rebuildWithTimeLimit = timeLimit => {
  let timeout = setTimeout(() => ctx.cancel(), timeLimit)
  return ctx.rebuild().finally(() => clearTimeout(timeout))
}

let build = await rebuildWithTimeLimit(500)
```
- Go:
```
ctx, err := api.Context(api.BuildOptions{
  // ...
})
if err != nil {
  return
}

rebuildWithTimeLimit := func(timeLimit time.Duration) api.BuildResult {
  t := time.NewTimer(timeLimit)
  go func() {
    <-t.C
    ctx.Cancel()
  }()
  result := ctx.Rebuild()
  t.Stop()
  return result
}

build := rebuildWithTimeLimit(500 * time.Millisecond)
```
This API is a quick implementation and isn't maximally efficient, so the build may continue to do some work for a little bit before stopping. For example, I have added stop points between each top-level phase of the bundler and in the main module graph traversal loop, but I haven't added fine-grained stop points within the internals of the linker. How quickly esbuild stops can be improved in future releases. This means you'll want to wait for cancel() and/or the previous rebuild() to finish (i.e. await the returned promise in JavaScript) before starting a new build, otherwise rebuild() will give you the just-canceled build that still hasn't ended yet. Note that onEnd callbacks will still be run regardless of whether or not the build was canceled.
Fix server-sent events without servedir (#2827)

The server-sent events for live reload were incorrectly using servedir to calculate the path to modified output files. This means events couldn't be sent when servedir wasn't specified. This release uses the internal output directory (which is always present) instead of servedir (which might be omitted), so live reload should now work when servedir is not specified.
Custom entry point output paths now work with the copy loader (#2828)

Entry points can optionally provide custom output paths to change the path of the generated output file. For example, esbuild foo=abc.js bar=xyz.js --outdir=out generates the files out/foo.js and out/bar.js. However, this previously didn't work when using the copy loader due to an oversight. This bug has been fixed. For example, you can now do esbuild foo=abc.html bar=xyz.html --outdir=out --loader:.html=copy to generate the files out/foo.html and out/bar.html.

The JS API can now take an array of objects (#2828)

Previously it was not possible to specify two entry points with the same custom output path using the JS API, although it was possible to do this with the Go API and the CLI. This will not cause a collision if both entry points use different extensions (e.g. if one uses .js and the other uses .css). You can now pass the JS API an array of objects to work around this API limitation:

// The previous API didn't let you specify duplicate output paths
let result = await esbuild.build({
  entryPoints: {
    // This object literal contains a duplicate key, so one is ignored
    'dist': 'foo.js',
    'dist': 'bar.css',
  },
})

// You can now specify duplicate output paths as an array of objects
let result = await esbuild.build({
  entryPoints: [
    { in: 'foo.js', out: 'dist' },
    { in: 'bar.css', out: 'dist' },
  ],
})

0.17.0

This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild in your package.json file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.16.0 or ~0.16.0. See npm's documentation about semver for more information.

At a high level, the breaking changes in this release fix some long-standing issues with the design of esbuild's incremental, watch, and serve APIs. This release also introduces some exciting new features such as live reloading. In detail:

Move everything related to incremental builds to a new context API (#1037, #1606, #2280, #2418)

This change removes the incremental and watch options as well as the serve() method, and introduces a new context() method. The context method takes the same arguments as the build() method but only validates its arguments and does not do an initial build. Instead, builds can be triggered using the rebuild(), watch(), and serve() methods on the returned context object. The new context API looks like this:
```
// Create a context for incremental builds
const context = await esbuild.context({
  entryPoints: ['app.ts'],
  bundle: true,
})

// Manually do an incremental build
const result = await context.rebuild()

// Enable watch mode
await context.watch()

// Enable serve mode
await context.serve()

// Dispose of the context
context.dispose()
```
The switch to the context API solves a major issue with the previous API which is that if the initial build fails, a promise is thrown in JavaScript which prevents you from accessing the returned result object. That prevented you from setting up long-running operations such as watch mode when the initial build contained errors. It also makes tearing down incremental builds simpler as there is now a single way to do it instead of three separate ways.

In addition, this release also makes some subtle changes to how incremental builds work. Previously every call to rebuild() started a new build. If you weren't careful, then builds could actually overlap. This doesn't cause any problems with esbuild itself, but could potentially cause problems with plugins (esbuild doesn't even give you a way to identify which overlapping build a given plugin callback is running on). Overlapping builds also arguably aren't useful, or at least aren't useful enough to justify the confusion and complexity that they bring. With this release, there is now only ever a single active build per context. Calling rebuild() before the previous rebuild has finished now "merges" with the existing rebuild instead of starting a new build.
Allow using watch and serve together (#805, #1650, #2576)

Previously it was not possible to use watch mode and serve mode together. The rationale was that watch mode is one way of automatically rebuilding your project and serve mode is another (since serve mode automatically rebuilds on every request). However, people want to combine these two features to make "live reloading" where the browser automatically reloads the page when files are changed on the file system.

This release now allows you to use these two features together. You can only call the watch() and serve() APIs once each per context, but if you call them together on the same context then esbuild will automatically rebuild both when files on the file system are changed and when the server serves a request.
Support "live reloading" through server-sent events (#802)

Server-sent events are a simple way to pass one-directional messages asynchronously from the server to the client. Serve mode now provides a /esbuild endpoint with an change event that triggers every time esbuild's output changes. So you can now implement simple "live reloading" (i.e. reloading the page when a file is edited and saved) like this:
```
new EventSource('/esbuild').addEventListener('change', () => location.reload())
```
The event payload is a JSON object with the following shape:
```
interface ChangeEvent {
  added: string[]
  removed: string[]
  updated: string[]
}
```
This JSON should also enable more complex live reloading scenarios. For example, the following code hot-swaps changed CSS <link> tags in place without reloading the page (but still reloads when there are other types of changes):
```
new EventSource('/esbuild').addEventListener('change', e => {
  const { added, removed, updated } = JSON.parse(e.data)
  if (!added.length && !removed.length && updated.length === 1) {
    for (const link of document.getElementsByTagName("link")) {
      const url = new URL(link.href)
      if (url.host === location.host && url.pathname === updated[0]) {
        const next = link.cloneNode()
        next.href = updated[0] + '?' + Math.random().toString(36).slice(2)
        next.onload = () => link.remove()
        link.parentNode.insertBefore(next, link.nextSibling)
        return
      }
    }
  }
  location.reload()
})
```
Implementing live reloading like this has a few known caveats:
- These events only trigger when esbuild's output changes. They do not trigger when files unrelated to the build being watched are changed. If your HTML file references other files that esbuild doesn't know about and those files are changed, you can either manually reload the page or you can implement your own live reloading infrastructure instead of using esbuild's built-in behavior.
- The EventSource API is supposed to automatically reconnect for you. However, there's a bug in Firefox that breaks this if the server is ever temporarily unreachable: https://bugzilla.mozilla.org/show_bug.cgi?id=1809332. Workarounds are to use any other browser, to manually reload the page if this happens, or to write more complicated code that manually closes and re-creates the EventSource object if there is a connection error. I'm hopeful that this bug will be fixed.
- Browser vendors have decided to not implement HTTP/2 without TLS. This means that each /esbuild event source will take up one of your precious 6 simultaneous per-domain HTTP/1.1 connections. So if you open more than six HTTP tabs that use this live-reloading technique, you will be unable to use live reloading in some of those tabs (and other things will likely also break). The workaround is to enable HTTPS, which is now possible to do in esbuild itself (see below).
Add built-in support for HTTPS (#2169)

You can now tell esbuild's built-in development server to use HTTPS instead of HTTP. This is sometimes necessary because browser vendors have started making modern web features unavailable to HTTP websites. Previously you had to put a proxy in front of esbuild to enable HTTPS since esbuild's development server only supported HTTP. But with this release, you can now enable HTTPS with esbuild without an additional proxy.

To enable HTTPS with esbuild:
1. Generate a self-signed certificate. There are many ways to do this. Here's one way, assuming you have openssl installed:
```
openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 9999 -nodes -subj /CN=127.0.0.1
```
2. Add --keyfile=key.pem and --certfile=cert.pem to your esbuild development server command
3. Click past the scary warning in your browser when you load your page
If you have more complex needs than this, you can still put a proxy in front of esbuild and use that for HTTPS instead. Note that if you see the message "Client sent an HTTP request to an HTTPS server" when you load your page, then you are using the incorrect protocol. Replace http:// with https:// in your browser's URL bar.

Keep in mind that esbuild's HTTPS support has nothing to do with security. The only reason esbuild now supports HTTPS is because browsers have made it impossible to do local development with certain modern web features without jumping through these extra hoops. Please do not use esbuild's development server for anything that needs to be secure. It's only intended for local development and no considerations have been made for production environments whatsoever.
Better support copying index.html into the output directory (#621, #1771)

Right now esbuild only supports JavaScript and CSS as first-class content types. Previously this meant that if you were building a website with a HTML file, a JavaScript file, and a CSS file, you could use esbuild to build the JavaScript file and the CSS file into the output directory but not to copy the HTML file into the output directory. You needed a separate cp command for that.

Or so I thought. It turns out that the copy loader added in version 0.14.44 of esbuild is sufficient to have esbuild copy the HTML file into the output directory as well. You can add something like index.html --loader:.html=copy and esbuild will copy index.html into the output directory for you. The benefits of this are a) you don't need a separate cp command and b) the index.html file will automatically be re-copied when esbuild is in watch mode and the contents of index.html are edited. This also goes for other non-HTML file types that you might want to copy.

This pretty much already worked. The one thing that didn't work was that esbuild's built-in development server previously only supported implicitly loading index.html (e.g. loading /about/index.html when you visit /about/) when index.html existed on the file system. Previously esbuild didn't support implicitly loading index.html if it was a build result. That bug has been fixed with this release so it should now be practical to use the copy loader to do this.
Fix onEnd not being called in serve mode (#1384)

Previous releases had a bug where plugin onEnd callbacks weren't called when using the top-level serve() API. This API no longer exists and the internals have been reimplemented such that onEnd callbacks should now always be called at the end of every build.
Incremental builds now write out build results differently (#2104)

Previously build results were always written out after every build. However, this could cause the output directory to fill up with files from old builds if code splitting was enabled, since the file names for code splitting chunks contain content hashes and old files were not deleted.

With this release, incremental builds in esbuild will now delete old output files from previous builds that are no longer relevant. Subsequent incremental builds will also no longer overwrite output files whose contents haven't changed since the previous incremental build.
The onRebuild watch mode callback was removed (#980, #2499)

Previously watch mode accepted an onRebuild callback which was called whenever watch mode rebuilt something. This was not great in practice because if you are running code after a build, you likely want that code to run after every build, not just after the second and subsequent builds. This release removes option to provide an onRebuild callback. You can create a plugin with an onEnd callback instead. The onEnd plugin API already exists, and is a way to run some code after every build.
You can now return errors from onEnd (#2625)

It's now possible to add additional build errors and/or warnings to the current build from within your onEnd callback by returning them in an array. This is identical to how the onStart callback already works. The evaluation of onEnd callbacks have been moved around a bit internally to make this possible.

Note that the build will only fail (i.e. reject the promise) if the additional errors are returned from onEnd. Adding additional errors to the result object that's passed to onEnd won't affect esbuild's behavior at all.
Print URLs and ports from the Go and JS APIs (#2393)

Previously esbuild's CLI printed out something like this when serve mode is active:
```
 > Local:   http://127.0.0.1:8000/
 > Network: http://192.168.0.1:8000/
```
The CLI still does this, but now the JS and Go serve mode APIs will do this too. This only happens when the log level is set to verbose, debug, or info but not when it's set to warning, error, or silent.

Upgrade guide for existing code:

Rebuild (a.k.a. incremental build):

Before:

const result = await esbuild.build({ ...buildOptions, incremental: true });
builds.push(result);
for (let i = 0; i < 4; i++) builds.push(await result.rebuild());
await result.rebuild.dispose(); // To free resources

After:

const ctx = await esbuild.context(buildOptions);
for (let i = 0; i < 5; i++) builds.push(await ctx.rebuild());
await ctx.dispose(); // To free resources

Previously the first build was done differently than subsequent builds. Now both the first build and subsequent builds are done using the same API.

Serve:

Before:

const serveResult = await esbuild.serve(serveOptions, buildOptions);
...
serveResult.stop(); await serveResult.wait; // To free resources

After:

const ctx = await esbuild.context(buildOptions);
const serveResult = await ctx.serve(serveOptions);
...
await ctx.dispose(); // To free resources

Watch:

Before:

const result = await esbuild.build({ ...buildOptions, watch: true });
...
result.stop(); // To free resources

After:

const ctx = await esbuild.context(buildOptions);
await ctx.watch();
...
await ctx.dispose(); // To free resources

Watch with onRebuild:

Before:

const onRebuild = (error, result) => {
  if (error) console.log('subsequent build:', error);
  else console.log('subsequent build:', result);
};
try {
  const result = await esbuild.build({ ...buildOptions, watch: { onRebuild } });
  console.log('first build:', result);
  ...
  result.stop(); // To free resources
} catch (error) {
  console.log('first build:', error);
}

After:

const plugins = [{
  name: 'my-plugin',
  setup(build) {
    let count = 0;
    build.onEnd(result => {
      if (count++ === 0) console.log('first build:', result);
      else console.log('subsequent build:', result);
    });
  },
}];
const ctx = await esbuild.context({ ...buildOptions, plugins });
await ctx.watch();
...
await ctx.dispose(); // To free resources

The onRebuild function has now been removed. The replacement is to make a plugin with an onEnd callback.

Previously onRebuild did not fire for the first build (only for subsequent builds). This was usually problematic, so using onEnd instead of onRebuild is likely less error-prone. But if you need to emulate the old behavior of onRebuild that ignores the first build, then you'll need to manually count and ignore the first build in your plugin (as demonstrated above).

Notice how all of these API calls are now done off the new context object. You should now be able to use all three kinds of incremental builds (rebuild, serve, and watch) together on the same context object. Also notice how calling dispose on the context is now the common way to discard the context and free resources in all of these situations.

0.16.17

Fix additional comment-related regressions (#2814)

This release fixes more edge cases where the new comment preservation behavior that was added in 0.16.14 could introduce syntax errors. Specifically:
```
x = () => (/* comment */ {})
for ((/* comment */ let).x of y) ;
function *f() { yield (/* comment */class {}) }
```
These cases caused esbuild to generate code with a syntax error in version 0.16.14 or above. These bugs have now been fixed.

0.16.16

Fix a regression caused by comment preservation (#2805)

The new comment preservation behavior that was added in 0.16.14 introduced a regression where comments in certain locations could cause esbuild to omit certain necessary parentheses in the output. The outermost parentheses were incorrectly removed for the following syntax forms, which then introduced syntax errors:
```
(/* comment */ { x: 0 }).x;
(/* comment */ function () { })();
(/* comment */ class { }).prototype;
```
This regression has been fixed.

0.16.15

Add format to input files in the JSON metafile data

When --metafile is enabled, input files may now have an additional format field that indicates the export format used by this file. When present, the value will either be cjs for CommonJS-style exports or esm for ESM-style exports. This can be useful in bundle analysis.

For example, esbuild's new Bundle Size Analyzer now uses this information to visualize whether ESM or CommonJS was used for each directory and file of source code (click on the CJS/ESM bar at the top).

This information is helpful when trying to reduce the size of your bundle. Using the ESM variant of a dependency instead of the CommonJS variant always results in a faster and smaller bundle because it omits CommonJS wrappers, and also may result in better tree-shaking as it allows esbuild to perform tree-shaking at the statement level instead of the module level.
Fix a bundling edge case with dynamic import (#2793)

This release fixes a bug where esbuild's bundler could produce incorrect output. The problematic edge case involves the entry point importing itself using a dynamic import() expression in an imported file, like this:
```
// src/a.js
export const A = 42;

// src/b.js
export const B = async () => (await import(".")).A

// src/index.js
export * from "./a"
export * from "./b"
```
Remove new type syntax from type declarations in the esbuild package (#2798)

Previously you needed to use TypeScript 4.3 or newer when using the esbuild package from TypeScript code due to the use of a getter in an interface in node_modules/esbuild/lib/main.d.ts. This release removes this newer syntax to allow people with versions of TypeScript as far back as TypeScript 3.5 to use this latest version of the esbuild package. Here is change that was made to esbuild's type declarations:
```
 export interface OutputFile {
   /** "text" as bytes */
   contents: Uint8Array;
   /** "contents" as text (changes automatically with "contents") */
-  get text(): string;
+  readonly text: string;
 }
```

0.16.14

Preserve some comments in expressions (#2721)

Various tools give semantic meaning to comments embedded inside of expressions. For example, Webpack and Vite have special "magic comments" that can be used to affect code splitting behavior:
```
import(/* webpackChunkName: "foo" */ '../foo');
import(/* @vite-ignore */ dynamicVar);
new Worker(/* webpackChunkName: "bar" */ new URL("../bar.ts", import.meta.url));
new Worker(new URL('./path', import.meta.url), /* @vite-ignore */ dynamicOptions);
```
Since esbuild can be used as a preprocessor for these tools (e.g. to strip TypeScript types), it can be problematic if esbuild doesn't do additional work to try to retain these comments. Previously esbuild special-cased Webpack comments in these specific locations in the AST. But Vite would now like to use similar comments, and likely other tools as well.

So with this release, esbuild now will attempt to preserve some comments inside of expressions in more situations than before. This behavior is mainly intended to preserve these special "magic comments" that are meant for other tools to consume, although esbuild will no longer only preserve Webpack-specific comments so it should now be tool-agnostic. There is no guarantee that all such comments will be preserved (especially when --minify-syntax is enabled). So this change does not mean that esbuild is now usable as a code formatter. In particular comment preservation is more likely to happen with leading comments than with trailing comments. You should put comments that you want to be preserved before the relevant expression instead of after it. Also note that this change does not retain any more statement-level comments than before (i.e. comments not embedded inside of expressions). Comment preservation is not enabled when --minify-whitespace is enabled (which is automatically enabled when you use --minify).

0.16.13

Publish a new bundle visualization tool

While esbuild provides bundle metadata via the --metafile flag, previously esbuild left analysis of it completely up to third-party tools (well, outside of the rudimentary --analyze flag). However, the esbuild website now has a built-in bundle visualization tool:
- https://esbuild.github.io/analyze/
You can pass --metafile to esbuild to output bundle metadata, then upload that JSON file to this tool to visualize your bundle. This is helpful for answering questions such as:
- Which packages are included in my bundle?
- How did a specific file get included?
- How small did a specific file compress to?
- Was a specific file tree-shaken or not?
I'm publishing this tool because I think esbuild should provide some answer to "how do I visualize my bundle" without requiring people to reach for third-party tools. At the moment the tool offers two types of visualizations: a radial "sunburst chart" and a linear "flame chart". They serve slightly different but overlapping use cases (e.g. the sunburst chart is more keyboard-accessible while the flame chart is easier with the mouse). This tool may continue to evolve over time.
Fix --metafile and --mangle-cache with --watch (#1357)

The CLI calls the Go API and then also writes out the metafile and/or mangle cache JSON files if those features are enabled. This extra step is necessary because these files are returned by the Go API as in-memory strings. However, this extra step accidentally didn't happen for all builds after the initial build when watch mode was enabled. This behavior used to work but it was broken in version 0.14.18 by the introduction of the mangle cache feature. This release fixes the combination of these features, so the metafile and mangle cache features should now work with watch mode. This behavior was only broken for the CLI, not for the JS or Go APIs.
Add an original field to the metafile

The metadata file JSON now has an additional field: each import in an input file now contains the pre-resolved path in the original field in addition to the post-resolved path in the path field. This means it's now possible to run certain additional analysis over your bundle. For example, you should be able to use this to detect when the same package subpath is represented multiple times in the bundle, either because multiple versions of a package were bundled or because a package is experiencing the dual-package hazard.

2022

All esbuild versions published in the year 2022 (versions 0.14.11 through 0.16.12) can be found in CHANGELOG-2022.md.

2021

All esbuild versions published in the year 2021 (versions 0.8.29 through 0.14.10) can be found in CHANGELOG-2021.md.

2020

All esbuild versions published in the year 2020 (versions 0.3.0 through 0.8.28) can be found in CHANGELOG-2020.md.

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Changelog

Unreleased

0.20.2

0.20.1

0.20.0

0.19.12

0.19.11

0.19.10

0.19.9

0.19.8

0.19.7

0.19.6

0.19.5

0.19.4

0.19.3

0.19.2

0.19.1

0.19.0

0.18.20

0.18.19

0.18.18

0.18.17

0.18.16

0.18.15

0.18.14

0.18.13

0.18.12

0.18.11

0.18.10

0.18.9

0.18.8

0.18.7

0.18.6

0.18.5

0.18.4

0.18.3

0.18.2

0.18.1

0.18.0

0.17.19

0.17.18

0.17.17

0.17.16

0.17.15

0.17.14

0.17.13

0.17.12

0.17.11

0.17.10

0.17.9

0.17.8

0.17.7

0.17.6

0.17.5

0.17.4

0.17.3

0.17.2

0.17.1

0.17.0

Upgrade guide for existing code:

0.16.17

0.16.16

0.16.15

0.16.14

0.16.13

2022

2021

2020