v0.18.1

• 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).

v0.18.0

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 fe...

v0.17.19

• 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);

v0.17.18

• 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.

v0.17.17

• 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.

v0.17.16

• 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.

v0.17.15

• 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.

v0.17.14

• 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}

v0.17.13

• 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}

v0.17.12

• 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.