Export custom TypeScript worker variables

[remcohaszing]

A custom TypeScript worker factory function gets passed TypeScriptWorker, ts, and libFileMap. It also exports create using ESM. However, this can’t be used, because the custom worker factory is only called if a custom worker path is defined.

Exposing these members, means a worker can be defined using ESM.

A practical use case:

/**
 * @typedef {import('monaco-editor').languages.typescript.CompilerOptions} CompilerOptions
 * @typedef {import('monaco-editor').languages.typescript.IExtraLibs} IExtraLibs
 * @typedef {import('monaco-editor').languages.typescript.InlayHintsOptions} InlayHintsOptions
 * @typedef {import('monaco-editor').languages.typescript.TypeScriptWorker} TypeScriptWorker
 * @typedef {import('monaco-editor').worker.IWorkerContext} IWorkerContext
 * @typedef {import('typescript').LanguageServiceHost} LanguageServiceHost
 *
 * @typedef {object} CreateData
 * @property {CompilerOptions} compilerOptions The TypeScript compiler options configured by the user.
 * @property {string} customWorkerPath The path to a custom worker.
 * @property {IExtraLibs} extraLibs Additional libraries to load.
 * @property {InlayHintsOptions} inlayHintsOptions The TypeScript inlay hints options.
 *
 * @typedef {TypeScriptWorker & LanguageServiceHost} MDXWorker
 * @typedef {new (ctx: IWorkerContext, createData: CreateData) => MDXWorker} TypeScriptWorkerClass
 */

import {createMdxLanguageService} from '@mdx-js/language-service'
// @ts-expect-error This module is untyped.
import {initialize} from 'monaco-editor/esm/vs/editor/editor.worker.js'
// @ts-expect-error This module is untyped.
import {create} from 'monaco-editor/esm/vs/language/typescript/ts.worker.js'

/**
 * @param {TypeScriptWorkerClass} TypeScriptWorker
 * @returns {TypeScriptWorkerClass} A custom TypeScript worker which knows how to handle MDX.
 */
function worker(TypeScriptWorker) {
  return class MDXWorker extends TypeScriptWorker {
    _languageService = createMdxLanguageService(
      // @ts-expect-error This is globally defined in the worker.
      ts,
      this
    )
  }
}

// @ts-expect-error This is missing in the Monaco type definitions.
self.customTSWorkerFactory = worker

// Trick the TypeScript worker into using the `customTSWorkerFactory`
self.importScripts = () => {}

self.onmessage = () => {
  initialize(
    /**
     * @param {IWorkerContext} ctx
     * @param {CreateData} createData
     * @returns {MDXWorker} The MDX TypeScript worker.
     */
    (ctx, createData) => create(ctx, {...createData, customWorkerPath: true})
  )
}

becomes:

/**
 * @typedef {import('monaco-editor').languages.typescript.CompilerOptions} CompilerOptions
 * @typedef {import('monaco-editor').languages.typescript.IExtraLibs} IExtraLibs
 * @typedef {import('monaco-editor').languages.typescript.InlayHintsOptions} InlayHintsOptions
 * @typedef {import('monaco-editor').languages.typescript.TypeScriptWorker} TypeScriptWorker
 * @typedef {import('monaco-editor').worker.IWorkerContext} IWorkerContext
 *
 * @typedef {object} CreateData
 * @property {CompilerOptions} compilerOptions The TypeScript compiler options configured by the user.
 * @property {string} customWorkerPath The path to a custom worker.
 * @property {IExtraLibs} extraLibs Additional libraries to load.
 * @property {InlayHintsOptions} inlayHintsOptions The TypeScript inlay hints options.
 */

import {createMdxLanguageService} from '@mdx-js/language-service'
import {
  initialize,
  ts,
  TypeScriptWorker
  // @ts-expect-error This module is untyped.
} from 'monaco-editor/esm/vs/language/typescript/ts.worker.js'

class MDXWorker extends TypeScriptWorker {
  _languageService = createMdxLanguageService(
    ts,
    // @ts-expect-error This is missing in the Monaco type definitions.
    this
  )
}

self.onmessage = () => {
  initialize(
    /**
     * @param {IWorkerContext} ctx
     * @param {CreateData} createData
     * @returns {MDXWorker} The MDX TypeScript worker.
     */
    (ctx, createData) =>
      // @ts-expect-error This is missing in the Monaco type definitions.
      new MDXWorker(ctx, createData)
  )
}

[hediet]

Thanks for the PR! Sorry for not looking at it early.