Changelog

Unreleased

• Fix node-specific annotations for string literal export names (#4100)

  When node instantiates a CommonJS module, it scans the AST to look for names to expose via ESM named exports. This is a heuristic that looks for certain patterns such as exports.NAME = ... or module.exports = { ... }. This behavior is used by esbuild to "annotate" CommonJS code that was converted from ESM with the original ESM export names. For example, when converting the file export let foo, bar from ESM to CommonJS, esbuild appends this to the end of the file:

  // Annotate the CommonJS export names for ESM import in node:
  0 && (module.exports = {
    bar,
    foo
  });
  

  However, this feature previously didn't work correctly for export names that are not valid identifiers, which can be constructed using string literal export names. The generated code contained a syntax error. That problem is fixed in this release:

  // Original code
  let foo
  export { foo as "foo!" }
  
  // Old output (with --format=cjs --platform=node)
  ...
  0 && (module.exports = {
    "foo!"
  });
  
  // New output (with --format=cjs --platform=node)
  ...
  0 && (module.exports = {
    "foo!": null
  });
  

• Basic support for index source maps (#3439, #4109)

  The source map specification has an optional mode called index source maps that makes it easier for tools to create an aggregate JavaScript file by concatenating many smaller JavaScript files with source maps, and then generate an aggregate source map by simply providing the original source maps along with some offset information. My understanding is that this is rarely used in practice. I'm only aware of two uses of it in the wild: ClojureScript and Turbopack.

  This release provides basic support for indexed source maps. However, the implementation has not been tested on a real app (just on very simple test input). If you are using index source maps in a real app, please try this out and report back if anything isn't working for you.

  Note that this is also not a complete implementation. For example, index source maps technically allows nesting source maps to an arbitrary depth, while esbuild's implementation in this release only supports a single level of nesting. It's unclear whether supporting more than one level of nesting is important or not given the lack of available test cases.

  This feature was contributed by @clyfish.

0.25.1

• Fix incorrect paths in inline source maps (#4070, #4075, #4105)

  This fixes a regression from version 0.25.0 where esbuild didn't correctly resolve relative paths contained within source maps in inline sourceMappingURL data URLs. The paths were incorrectly being passed through as-is instead of being resolved relative to the source file containing the sourceMappingURL comment, which was due to the data URL not being a file URL. This regression has been fixed, and this case now has test coverage.

• Fix invalid generated source maps (#4080, #4082, #4104, #4107)

  This release fixes a regression from version 0.24.1 that could cause esbuild to generate invalid source maps. Specifically under certain conditions, esbuild could generate a mapping with an out-of-bounds source index. It was introduced by code that attempted to improve esbuild's handling of "null" entries in source maps (i.e. mappings with a generated position but no original position). This regression has been fixed.

  This fix was contributed by @jridgewell.

• Fix a regression with non-file source map paths (#4078)

  The format of paths in source maps that aren't in the file namespace was unintentionally changed in version 0.25.0. Path namespaces is an esbuild-specific concept that is optionally available for plugins to use to distinguish paths from file paths and from paths meant for other plugins. Previously the namespace was prepended to the path joined with a : character, but version 0.25.0 unintentionally failed to prepend the namespace. The previous behavior has been restored.

• Fix a crash with switch optimization (#4088)

  The new code in the previous release to optimize dead code in switch statements accidentally introduced a crash in the edge case where one or more switch case values include a function expression. This is because esbuild now visits the case values first to determine whether any cases are dead code, and then visits the case bodies once the dead code status is known. That triggered some internal asserts that guard against traversing the AST in an unexpected order. This crash has been fixed by changing esbuild to expect the new traversal ordering. Here's an example of affected code:

  switch (x) {
    case '':
      return y.map(z => z.value)
    case y.map(z => z.key).join(','):
      return []
  }
  

• Update Go from 1.23.5 to 1.23.7 (#4076, #4077)

  This should have no effect on existing code as this version change does not change Go's operating system support. It may remove certain reports from vulnerability scanners that detect which version of the Go compiler esbuild uses.

  This PR was contributed by @MikeWillCook.

0.25.0

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 ^0.24.0 or ~0.24.0. See npm's documentation about semver for more information.

• Restrict access to esbuild's development server (GHSA-67mh-4wv8-2f99)

  This change addresses esbuild's first security vulnerability report. Previously esbuild set the Access-Control-Allow-Origin header to * to allow esbuild's development server to be flexible in how it's used for development. However, this allows the websites you visit to make HTTP requests to esbuild's local development server, which gives read-only access to your source code if the website were to fetch your source code's specific URL. You can read more information in the report.

  Starting with this release, CORS will now be disabled, and requests will now be denied if the host does not match the one provided to --serve=. The default host is 0.0.0.0, which refers to all of the IP addresses that represent the local machine (e.g. both 127.0.0.1 and 192.168.0.1). If you want to customize anything about esbuild's development server, you can put a proxy in front of esbuild and modify the incoming and/or outgoing requests.

  In addition, the serve() API call has been changed to return an array of hosts instead of a single host string. This makes it possible to determine all of the hosts that esbuild's development server will accept.

  Thanks to @sapphi-red for reporting this issue.

• Delete output files when a build fails in watch mode (#3643)

  It has been requested for esbuild to delete files when a build fails in watch mode. Previously esbuild left the old files in place, which could cause people to not immediately realize that the most recent build failed. With this release, esbuild will now delete all output files if a rebuild fails. Fixing the build error and triggering another rebuild will restore all output files again.

• Fix correctness issues with the CSS nesting transform (#3620, #3877, #3933, #3997, #4005, #4037, #4038)

  This release fixes the following problems:

  • Naive expansion of CSS nesting can result in an exponential blow-up of generated CSS if each nesting level has multiple selectors. Previously esbuild sometimes collapsed individual nesting levels using :is() to limit expansion. However, this collapsing wasn't correct in some cases, so it has been removed to fix correctness issues.

    /* Original code */
    .parent {
      > .a,
      > .b1 > .b2 {
        color: red;
      }
    }
    
    /* Old output (with --supported:nesting=false) */
    .parent > :is(.a, .b1 > .b2) {
      color: red;
    }
    
    /* New output (with --supported:nesting=false) */
    .parent > .a,
    .parent > .b1 > .b2 {
      color: red;
    }
    

    Thanks to @tim-we for working on a fix.

  • The & CSS nesting selector can be repeated multiple times to increase CSS specificity. Previously esbuild ignored this possibility and incorrectly considered && to have the same specificity as &. With this release, this should now work correctly:

    /* Original code (color should be red) */
    div {
      && { color: red }
      & { color: blue }
    }
    
    /* Old output (with --supported:nesting=false) */
    div {
      color: red;
    }
    div {
      color: blue;
    }
    
    /* New output (with --supported:nesting=false) */
    div:is(div) {
      color: red;
    }
    div {
      color: blue;
    }
    

    Thanks to @CPunisher for working on a fix.

  • Previously transforming nested CSS incorrectly removed leading combinators from within pseudoclass selectors such as :where(). This edge case has been fixed and how has test coverage.

    /* Original code */
    a b:has(> span) {
      a & {
        color: green;
      }
    }
    
    /* Old output (with --supported:nesting=false) */
    a :is(a b:has(span)) {
      color: green;
    }
    
    /* New output (with --supported:nesting=false) */
    a :is(a b:has(> span)) {
      color: green;
    }
    

    This fix was contributed by @NoremacNergfol.

  • The CSS minifier contains logic to remove the & selector when it can be implied, which happens when there is only one and it's the leading token. However, this logic was incorrectly also applied to selector lists inside of pseudo-class selectors such as :where(). With this release, the minifier will now avoid applying this logic in this edge case:

    /* Original code */
    .a {
      & .b { color: red }
      :where(& .b) { color: blue }
    }
    
    /* Old output (with --minify) */
    .a{.b{color:red}:where(.b){color:#00f}}
    
    /* New output (with --minify) */
    .a{.b{color:red}:where(& .b){color:#00f}}
    

• Fix some correctness issues with source maps (#1745, #3183, #3613, #3982)

  Previously esbuild incorrectly treated source map path references as file paths instead of as URLs. With this release, esbuild will now treat source map path references as URLs. This fixes the following problems with source maps:

  • File names in sourceMappingURL that contained a space previously did not encode the space as %20, which resulted in JavaScript tools (including esbuild) failing to read that path back in when consuming the generated output file. This should now be fixed.

  • Absolute URLs in sourceMappingURL that use the file:// scheme previously attempted to read from a folder called file:. These URLs should now be recognized and parsed correctly.

  • Entries in the sources array in the source map are now treated as URLs instead of file paths. The correct behavior for this is much more clear now that source maps has a formal specification. Many thanks to those who worked on the specification.

• Fix incorrect package for @esbuild/netbsd-arm64 (#4018)

  Due to a copy+paste typo, the binary published to @esbuild/netbsd-arm64 was not actually for arm64, and didn't run in that environment. This release should fix running esbuild in that environment (NetBSD on 64-bit ARM). Sorry about the mistake.

• Fix a minification bug with bitwise operators and bigints (#4065)

  This change removes an incorrect assumption in esbuild that all bitwise operators result in a numeric integer. That assumption was correct up until the introduction of bigints in ES2020, but is no longer correct because almost all bitwise operators now operate on both numbers and bigints. Here's an example of the incorrect minification:

  // Original code
  if ((a & b) !== 0) found = true
  
  // Old output (with --minify)
  a&b&&(found=!0);
  
  // New output (with --minify)
  (a&b)!==0&&(found=!0);
  

• Fix esbuild incorrectly rejecting valid TypeScript edge case (#4027)

  The following TypeScript code is valid:

  export function open(async?: boolean): void {
    console.log(async as boolean)
  }
  

  Before this version, esbuild would fail to parse this with a syntax error as it expected the token sequence async as ... to be the start of an async arrow function expression async as => .... This edge case should be parsed correctly by esbuild starting with this release.

• Transform BigInt values into constructor calls when unsupported (#4049)

  Previously esbuild would refuse to compile the BigInt literals (such as 123n) if they are unsupported in the configured target environment (such as with --target=es6). The rationale was that they cannot be polyfilled effectively because they change the behavior of JavaScript's arithmetic operators and JavaScript doesn't have operator overloading.

  However, this prevents using esbuild with certain libraries that would otherwise work if BigInt literals were ignored, such as with old versions of the buffer library before the library fixed support for running in environments without BigInt support. So with this release, esbuild will now turn BigInt literals into BigInt constructor calls (so 123n becomes BigInt(123)) and generate a warning in this case. You can turn off the warning with --log-override:bigint=silent or restore the warning to an error with --log-override:bigint=error if needed.

• Change how console API dropping works (#4020)

  Previously the --drop:console feature replaced all method calls off of the console global with undefined regardless of how long the property access chain was (so it applied to console.log() and console.log.call(console) and console.log.not.a.method()). However, it was pointed out that this breaks uses of console.log.bind(console). That's also incompatible with Terser's implementation of the feature, which is where this feature originally came from (it does support bind). So with this release, using this feature with esbuild will now only replace one level of method call (unless extended by call or apply) and will replace the method being called with an empty function in complex cases:

  // Original code
  const x = console.log('x')
  const y = console.log.call(console, 'y')
  const z = console.log.bind(console)('z')
  
  // Old output (with --drop-console)
  const x = void 0;
  const y = void 0;
  const z = (void 0)("z");
  
  // New output (with --drop-console)
  const x = void 0;
  const y = void 0;
  const z = (() => {
  }).bind(console)("z");
  

  This should more closely match Terser's existing behavior.

• Allow BigInt literals as define values

  With this release, you can now use BigInt literals as define values, such as with --define:FOO=123n. Previously trying to do this resulted in a syntax error.

• Fix a bug with resolve extensions in node_modules (#4053)

  The --resolve-extensions= option lets you specify the order in which to try resolving implicit file extensions. For complicated reasons, esbuild reorders TypeScript file extensions after JavaScript ones inside of node_modules so that JavaScript source code is always preferred to TypeScript source code inside of dependencies. However, this reordering had a bug that could accidentally change the relative order of TypeScript file extensions if one of them was a prefix of the other. That bug has been fixed in this release. You can see the issue for details.

• Better minification of statically-determined switch cases (#4028)

  With this release, esbuild will now try to trim unused code within switch statements when the test expression and case expressions are primitive literals. This can arise when the test expression is an identifier that is substituted for a primitive literal at compile time. For example:

  // Original code
  switch (MODE) {
    case 'dev':
      installDevToolsConsole()
      break
    case 'prod':
      return
    default:
      throw new Error
  }
  
  // Old output (with --minify '--define:MODE="prod"')
  switch("prod"){case"dev":installDevToolsConsole();break;case"prod":return;default:throw new Error}
  
  // New output (with --minify '--define:MODE="prod"')
  return;
  

• Emit /* @__KEY__ */ for string literals derived from property names (#4034)

  Property name mangling is an advanced feature that shortens certain property names for better minification (I say "advanced feature" because it's very easy to break your code with it). Sometimes you need to store a property name in a string, such as obj.get('foo') instead of obj.foo. JavaScript minifiers such as esbuild and Terser have a convention where a /* @__KEY__ */ comment before the string makes it behave like a property name. So obj.get(/* @__KEY__ */ 'foo') allows the contents of the string 'foo' to be shortened.

  However, esbuild sometimes itself generates string literals containing property names when transforming code, such as when lowering class fields to ES6 or when transforming TypeScript decorators. Previously esbuild didn't generate its own /* @__KEY__ */ comments in this case, which means that minifying your code by running esbuild again on its own output wouldn't work correctly (this does not affect people that both minify and transform their code in a single step).

  With this release, esbuild will now generate /* @__KEY__ */ comments for property names in generated string literals. To avoid lots of unnecessary output for people that don't use this advanced feature, the generated comments will only be present when the feature is active. If you want to generate the comments but not actually mangle any property names, you can use a flag that has no effect such as --reserve-props=., which tells esbuild to not mangle any property names (but still activates this feature).

• The text loader now strips the UTF-8 BOM if present (#3935)

  Some software (such as Notepad on Windows) can create text files that start with the three bytes 0xEF 0xBB 0xBF, which is referred to as the "byte order mark". This prefix is intended to be removed before using the text. Previously esbuild's text loader included this byte sequence in the string, which turns into a prefix of \uFEFF in a JavaScript string when decoded from UTF-8. With this release, esbuild's text loader will now remove these bytes when they occur at the start of the file.

• Omit legal comment output files when empty (#3670)

  Previously configuring esbuild with --legal-comment=external or --legal-comment=linked would always generate a .LEGAL.txt output file even if it was empty. Starting with this release, esbuild will now only do this if the file will be non-empty. This should result in a more organized output directory in some cases.

• Update Go from 1.23.1 to 1.23.5 (#4056, #4057)

  This should have no effect on existing code as this version change does not change Go's operating system support. It may remove certain reports from vulnerability scanners that detect which version of the Go compiler esbuild uses.

  This PR was contributed by @MikeWillCook.

• Allow passing a port of 0 to the development server (#3692)

  Unix sockets interpret a port of 0 to mean "pick a random unused port in the ephemeral port range". However, esbuild's default behavior when the port is not specified is to pick the first unused port starting from 8000 and upward. This is more convenient because port 8000 is typically free, so you can for example restart the development server and reload your app in the browser without needing to change the port in the URL. Since esbuild is written in Go (which does not have optional fields like JavaScript), not specifying the port in Go means it defaults to 0, so previously passing a port of 0 to esbuild caused port 8000 to be picked.

  Starting with this release, passing a port of 0 to esbuild when using the CLI or the JS API will now pass port 0 to the OS, which will pick a random ephemeral port. To make this possible, the Port option in the Go API has been changed from uint16 to int (to allow for additional sentinel values) and passing a port of -1 in Go now picks a random port. Both the CLI and JS APIs now remap an explicitly-provided port of 0 into -1 for the internal Go API.

  Another option would have been to change Port in Go from uint16 to *uint16 (Go's closest equivalent of number | undefined). However, that would make the common case of providing an explicit port in Go very awkward as Go doesn't support taking the address of integer constants. This tradeoff isn't worth it as picking a random ephemeral port is a rare use case. So the CLI and JS APIs should now match standard Unix behavior when the port is 0, but you need to use -1 instead with Go API.

• Minification now avoids inlining constants with direct eval (#4055)

  Direct eval can be used to introduce a new variable like this:

  const variable = false
  ;(function () {
    eval("var variable = true")
    console.log(variable)
  })()
  

  Previously esbuild inlined variable here (which became false), which changed the behavior of the code. This inlining is now avoided, but please keep in mind that direct eval breaks many assumptions that JavaScript tools hold about normal code (especially when bundling) and I do not recommend using it. There are usually better alternatives that have a more localized impact on your code. You can read more about this here: https://esbuild.github.io/link/direct-eval/

2024

All esbuild versions published in the year 2024 (versions 0.19.12 through 0.24.2) can be found in CHANGELOG-2024.md.

2023

All esbuild versions published in the year 2023 (versions 0.16.13 through 0.19.11) can be found in CHANGELOG-2023.md.

2022

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

2021

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

2020

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