feat(worker-bundler): add typescript support for worker-bundler

[zebp]

Adds support for the TypeScript language service to @cloudflare/worker-bundler as well a new virtual file-system abstraction for interfacing with the code for bundled workers. This is primarily to allow efficient storage of Worker code in Durable Objects.

Example

const inputFileSystem = new InMemoryFileSystem({
  "package.json": JSON.stringify({
    dependencies: {
      "@cloudflare/workers-types": "^4.20260405.1"
    }
  }),
  "tsconfig.json": JSON.stringify({
    compilerOptions: {
      lib: ["es2024"],
      target: "ES2024",
      module: "ES2022",
      moduleResolution: "bundler",
      allowSyntheticDefaultImports: true,
      strict: true,
      skipLibCheck: true,
      types: ["@cloudflare/workers-types/index.d.ts"]
    }
  }),
  "src/index.ts": `
    const worker: ExportedHandler = {
    
    async fetch() {
        return new Response("Hello, world!");
      }
    };
    
    export default worker;
  `
});

const installResult = await installDependencies(inputFileSystem);
const { fileSystem, languageService } = await createTypescriptLanguageService({ fileSystem: inputFileSystem });

Separate ./typescript export

The TypeScript bundle is large (~5 MB minified). Importing it unconditionally from the main entry point would penalise every caller that only needs bundling. The language service is therefore exported under its own subpath:

import { createTypescriptLanguageService } from "@cloudflare/worker-bundler/typescript";

---

[changeset-bot]

🦋 Changeset detected

Latest commit: 7d5d661

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@cloudflare/ai-chat	Patch
@cloudflare/worker-bundler	Minor

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commit: 7d5d661

[threepointone]

working on this

[threepointone]

Made a few changes on top of this:

Bug fix: TypescriptFileSystem.write() was calling updateFile unconditionally, which throws for files not in the original root set. Now dispatches to createFile vs updateFile based on whether the source file already exists in the VFS. Added a regression test.

New utility: createFileSystemSnapshot — takes any sync/async iterable of [path, content] pairs and returns an InMemoryFileSystem. This bridges async storage backends (like Workspace from @cloudflare/shell) to the synchronous FileSystem interface needed by esbuild and TypeScript. Added tests.

Docs: Updated README with sections on the FileSystem interface, all three implementations, createFileSystemSnapshot, standalone installDependencies, the TypeScript language service (including Workspace integration), and a known limitation about the runtime lib declaration fetch.

Cleanup: Fixed OverlayFileSystem JSDoc (said "Not exported" but class is export class — clarified it's not re-exported from the package entry point). Fixed TypeScript license label in THIRD_PARTY_LICENSES.md (was "MIT", should be "Apache License 2.0"). Updated changeset to mention DurableObjectRawFileSystem and createFileSystemSnapshot.