evanw/esbuild v0.16.9

on GitHub

Update to Unicode 15.0.0

The character tables that determine which characters form valid JavaScript identifiers have been updated from Unicode version 14.0.0 to the newly-released Unicode version 15.0.0. I'm not putting an example in the release notes because all of the new characters will likely just show up as little squares since fonts haven't been updated yet. But you can read https://www.unicode.org/versions/Unicode15.0.0/#Summary for more information about the changes.

Disallow duplicate lexically-declared names in nested blocks and in strict mode

In strict mode or in a nested block, it's supposed to be a syntax error to declare two symbols with the same name unless all duplicate entries are either function declarations or all var declarations. However, esbuild was overly permissive and allowed this when duplicate entries were either function declarations or var declarations (even if they were mixed). This check has now been made more restrictive to match the JavaScript specification:

// JavaScript allows this
var a
function a() {}
{
  var b
  var b
  function c() {}
  function c() {}
}

// JavaScript doesn't allow this
{
  var d
  function d() {}
}

Add a type declaration for the new empty loader (#2755)

I forgot to add this in the previous release. It has now been added.

This fix was contributed by @fz6m.

Add support for the v flag in regular expression literals

People are currently working on adding a v flag to JavaScript regular expresions. You can read more about this flag here: https://v8.dev/features/regexp-v-flag. This release adds support for parsing this flag, so esbuild will now no longer consider regular expression literals with this flag to be a syntax error. If the target is set to something other than esnext, esbuild will transform regular expression literals containing this flag into a new RegExp() constructor call so the resulting code doesn't have a syntax error. This enables you to provide a polyfill for RegExp that implements the v flag to get your code to work at run-time. While esbuild doesn't typically adopt proposals until they're already shipping in a real JavaScript run-time, I'm adding it now because a) esbuild's implementation doesn't need to change as the proposal evolves, b) this isn't really new syntax since regular expression literals already have flags, and c) esbuild's implementation is a trivial pass-through anyway.

Avoid keeping the name of classes with static name properties

The --keep-names property attempts to preserve the original value of the name property for functions and classes even when identifiers are renamed by the minifier or to avoid a name collision. This is currently done by generating code to assign a string to the name property on the function or class object. However, this should not be done for classes with a static name property since in that case the explicitly-defined name property overwrites the automatically-generated class name. With this release, esbuild will now no longer attempt to preserve the name property for classes with a static name property.