evanw/esbuild v0.21.3

on GitHub

Implement the decorator metadata proposal (#3760)

This release implements the decorator metadata proposal, which is a sub-proposal of the decorators proposal. Microsoft shipped the decorators proposal in TypeScript 5.0 and the decorator metadata proposal in TypeScript 5.2, so it's important that esbuild also supports both of these features. Here's a quick example:

// Shim the "Symbol.metadata" symbol
Symbol.metadata ??= Symbol('Symbol.metadata')

const track = (_, context) => {
  (context.metadata.names ||= []).push(context.name)
}

class Foo {
  @track foo = 1
  @track bar = 2
}

// Prints ["foo", "bar"]
console.log(Foo[Symbol.metadata].names)

⚠️ WARNING ⚠️

This proposal has been marked as "stage 3" which means "recommended for implementation". However, it's still a work in progress and isn't a part of JavaScript yet, so keep in mind that any code that uses JavaScript decorator metadata may need to be updated as the feature continues to evolve. If/when that happens, I will update esbuild's implementation to match the specification. I will not be supporting old versions of the specification.

Fix bundled decorators in derived classes (#3768)

In certain cases, bundling code that uses decorators in a derived class with a class body that references its own class name could previously generate code that crashes at run-time due to an incorrect variable name. This problem has been fixed. Here is an example of code that was compiled incorrectly before this fix:

class Foo extends Object {
  @(x => x) foo() {
    return Foo
  }
}
console.log(new Foo().foo())

Fix tsconfig.json files inside symlinked directories (#3767)

This release fixes an issue with a scenario involving a tsconfig.json file that extends another file from within a symlinked directory that uses the paths feature. In that case, the implicit baseURL value should be based on the real path (i.e. after expanding all symbolic links) instead of the original path. This was already done for other files that esbuild resolves but was not yet done for tsconfig.json because it's special-cased (the regular path resolver can't be used because the information inside tsconfig.json is involved in path resolution). Note that this fix no longer applies if the --preserve-symlinks setting is enabled.