Sourced from esbuild-wasm's releases.

v0.15.18

• Performance improvements for both JS and CSS

  This release brings noticeable performance improvements for JS parsing and for CSS parsing and printing. Here's an example benchmark for using esbuild to pretty-print a single large minified CSS file and JS file:

  Test case	Previous release	This release
  4.8mb CSS file	19ms	11ms (1.7x faster)
  5.8mb JS file	36ms	32ms (1.1x faster)

  The performance improvements were very straightforward:

  • Identifiers were being scanned using a generic character advancement function instead of using custom inline code. Advancing past each character involved UTF-8 decoding as well as updating multiple member variables. This was sped up using loop that skips UTF-8 decoding entirely and that only updates member variables once at the end. This is faster because identifiers are plain ASCII in the vast majority of cases, so Unicode decoding is almost always unnecessary.

  • CSS identifiers and CSS strings were still being printed one character at a time. Apparently I forgot to move this part of esbuild's CSS infrastructure beyond the proof-of-concept stage. These were both very obvious in the profiler, so I think maybe I have just never profiled esbuild's CSS printing before?

  • There was unnecessary work being done that was related to source maps when source map output was disabled. I likely haven't observed this before because esbuild's benchmarks always have source maps enabled. This work is now disabled when it's not going to be used.

  I definitely should have caught these performance issues earlier. Better late than never I suppose.

v0.15.17

• Search for missing source map code on the file system (#2711)

  Source maps are JSON files that map from compiled code back to the original code. They provide the original source code using two arrays: sources (required) and sourcesContent (optional). When bundling is enabled, esbuild is able to bundle code with source maps that was compiled by other tools (e.g. with Webpack) and emit source maps that map all the way back to the original code (e.g. before Webpack compiled it).

  Previously if the input source maps omitted the optional sourcesContent array, esbuild would use null for the source content in the source map that it generates (since the source content isn't available). However, sometimes the original source code is actually still present on the file system. With this release, esbuild will now try to find the original source code using the path in the sources array and will use that instead of null if it was found.

• Fix parsing bug with TypeScript infer and extends (#2712)

  This release fixes a bug where esbuild incorrectly failed to parse valid TypeScript code that nests extends inside infer inside extends, such as in the example below:

  type A<T> = {};
  type B = {} extends infer T extends {} ? A<T> : never;

  TypeScript code that does this should now be parsed correctly.

• Use WebAssembly.instantiateStreaming if available (#1036, #1900)

  Currently the WebAssembly version of esbuild uses fetch to download esbuild.wasm and then WebAssembly.instantiate to compile it. There is a newer API called WebAssembly.instantiateStreaming that both downloads and compiles at the same time, which can be a performance improvement if both downloading and compiling are slow. With this release, esbuild now attempts to use WebAssembly.instantiateStreaming and falls back to the original approach if that fails.

  The implementation for this builds on a PR by @​lbwa.

• Preserve Webpack comments inside constructor calls (#2439)

  This improves the use of esbuild as a faster TypeScript-to-JavaScript frontend for Webpack, which has special magic comments inside new Worker() expressions that affect Webpack's behavior.

v0.15.16

• Add a package alias feature (#2191)

... (truncated)

Sourced from esbuild-wasm's changelog.

Changelog: 2020

This changelog documents all esbuild versions published in the year 2020 (versions 0.3.0 through 0.8.28).

0.8.28

• Add a --summary flag that prints helpful information after a build (#631)

  Normally esbuild's CLI doesn't print anything after doing a build if nothing went wrong. This allows esbuild to be used as part of a more complex chain of tools without the output cluttering the terminal. However, sometimes it is nice to have a quick overview in your terminal of what the build just did. You can now add the --summary flag when using the CLI and esbuild will print a summary of what the build generated. It looks something like this:

  $ ./esbuild --summary --bundle src/Three.js --outfile=build/three.js --sourcemap
  build/three.js      1.0mb ⚠️
  build/three.js.map  1.8mb
  ⚡ Done in 43ms
  

• Keep unused imports in TypeScript code in one specific case (#604)

  The official TypeScript compiler always removes imported symbols that aren't used as values when converting TypeScript to JavaScript. This is because these symbols could be types and not removing them could result in a run-time module instantiation failure because of missing exports. This even happens when the tsconfig.json setting "importsNotUsedAsValues" is set to "preserve". Doing this just keeps the import statement itself but confusingly still removes the imports that aren't used as values.

  Previously esbuild always exactly matched the behavior of the official TypeScript compiler regarding import removal. However, that is problematic when trying to use esbuild to compile a partial module such as when converting TypeScript to JavaScript inside a file written in the Svelte programming language. Here is an example:

  <script lang="ts">
    import Counter from './Counter.svelte';
    export let name: string = 'world';
  </script>
  <main>
    <h1>Hello {name}!</h1>
    <Counter />
  </main>

  The current Svelte compiler plugin for TypeScript only provides esbuild with the contents of the <script> tag so to esbuild, the import Counter appears to be unused and is removed.

  In this release, esbuild deliberately deviates from the behavior of the official TypeScript compiler if all of these conditions are met:

  • The "importsNotUsedAsValues" field in tsconfig.json must be present and must not be set to "remove". This is necessary because this is the only case where esbuild can assume that all imports are values instead of types. Any imports that are types will cause a type error when the code is run through the TypeScript type checker. To import types when the importsNotUsedAsValues setting is active, you must use the TypeScript-specific import type syntax instead.

  • You must not be using esbuild as a bundler. When bundling, esbuild needs to assume that it's not seeing a partial file because the bundling process requires renaming symbols to avoid cross-file name collisions.

  • You must not have identifier minification enabled. It's useless to preserve unused imports in this case because referencing them by name won't work anyway. And keeping the unused imports would be counter-productive to minification since they would be extra unnecessary data in the output file.

  This should hopefully allow esbuild to be used as a TypeScript-to-JavaScript converter for programming languages such as Svelte, at least in many cases. The build pipeline in esbuild wasn't designed for compiling partial modules and this still won't be a fully robust solution (e.g. some variables may be renamed to avoid name collisions in rare cases). But it's possible that these cases are very unlikely to come up in practice. Basically this change to keep unused imports in this case should be useful at best and harmless at worst.

• 2953831 publish 0.15.18 to npm
• a3ba2b2 perf release notes
• f0d8fdd oops: skip source maps for improved performance
• e49e093 css: optimize printing quoted unescaped strings
• a193324 css: improve identifier printing performance
• 83b5580 css: pretty-print test failures
• 2b8883c css: improve lexer identifier parsing performance
• f6f8b27 js: improve lexer identifier parsing performance
• decf208 restrict gc disable to not serve or watch mode
• 2030df1 don't disable the gc with multiple entry points
• Additional commits viewable in compare view

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