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chore(deps): update dependency esbuild to ^0.19.0

Renovate Bot requested to merge renovate/esbuild-0.x into main

This MR contains the following updates:

Package Type Update Change
esbuild devDependencies minor ^0.18.0 -> ^0.19.0

Release Notes

evanw/esbuild (esbuild)

v0.19.0

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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.

v0.18.20

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  • 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).

v0.18.19

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  • 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.

v0.18.18

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  • 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;
}

v0.18.17

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  • 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 {}

v0.18.16

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  • 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.

v0.18.15

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  • 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.

v0.18.14

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  • 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;
}

v0.18.13

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  • 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:

v0.18.12

Compare Source

  • 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.

v0.18.11

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  • 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 = {}));

v0.18.10

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  • 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.

v0.18.9

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  • 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.

v0.18.8

Compare Source

  • 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.

v0.18.7

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  • 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 MR 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).

v0.18.6

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  • 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);
}

v0.18.5

Compare Source

  • 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.

v0.18.4

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  • 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:

    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};

v0.18.3

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  • 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.

v0.18.2

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  • 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).

v0.18.1

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  • 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.

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