v0.18.1

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

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

• Support /* @__KEY__ */ comments for mangling property names (#2574)

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

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

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

• Support /* @__NO_SIDE_EFFECTS__ */ comments for functions (#3149)

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

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