Give plugins access to build options

[eulores]

I am writing a plugin to compile Imba code. The plugin needs to be able to resolve files with .imba extension.

Therefore, .imba needs to be added to resolveExtensions when triggering the build process.
Right now the whole array gets overwritten:
resolveExtensions: [".tsx", ".ts", ".jsx", ".mjs", ".cjs", ".js", ".json", ".imba"]

I propose to let plugins return a string or an array of additional extensions to add to resolveExtensions.

export interface LoaderResult {
  errors?: PartialMessage[];
  warnings?: PartialMessage[];

  contents?: string | Uint8Array;
  loader?: Loader;
  resolveExtensions?: string | Uint8Array;
}

[eulores]

I fear I made a bad proposal.
Probably better to add another function (addExtension) to the Plugin interface.

[evanw]

I think other bundler plugin APIs give plugins the ability to modify the user-specified options object. I think that should be sufficient for this and other use cases. Something like addExtension doesn't seem sufficient because it wouldn't necessarily let you specify the exact resolution order.

[eulores]

Having the ability to modify the options object from within the plugin would indeed be perfect!
Right now I did not find that possibility. Am I missing something?
Thanks!

[evanw]

Support for this is in the latest release. Documentation is here: https://esbuild.github.io/plugins/#build-options.