refactor(client): allow TS worker to initialize itself and have the client check readiness (#57055)

client/src/templates/Challenges/rechallenge/transformers.js

@@ -20,7 +20,7 @@ import {
 import { WorkerExecutor } from '../utils/worker-executor';
 import {
   compileTypeScriptCode,
-  initTypeScriptService
+  checkTSServiceIsReady
 } from '../utils/typescript-worker-handler';
 
 const { filename: sassCompile } = sassData;
@@ -146,7 +146,7 @@ const babelTransformer = loopProtectOptions => {
       testTypeScript,
       async challengeFile => {
         await loadBabel();
-        await initTypeScriptService();
+        await checkTSServiceIsReady();
         const babelOptions = getBabelOptions(presetsJS, loopProtectOptions);
         return flow(
           partial(transformHeadTailAndContents, compileTypeScriptCode),

client/src/templates/Challenges/utils/typescript-worker-handler.ts

@@ -30,10 +30,10 @@ export function compileTypeScriptCode(code: string): Promise<string> {
   });
 }
 
-export function initTypeScriptService(): Promise<boolean> {
+export function checkTSServiceIsReady(): Promise<boolean> {
   return awaitResponse({
     worker: getTypeScriptWorker(),
-    message: { type: 'init' },
+    message: { type: 'check-is-ready' },
     onMessage: (data, onSuccess) => {
       if (data.type === 'ready') {
         onSuccess(true);

tools/client-plugins/browser-scripts/index.d.ts

@@ -1,4 +1,4 @@
-import { PyodideInterface } from 'pyodide';
+import type { PyodideInterface } from 'pyodide';
 
 export interface FrameDocument extends Document {
   __initTestFrame: (e: InitTestFrameArg) => Promise<void>;

tools/client-plugins/browser-scripts/package.json

@@ -20,8 +20,9 @@
   "main": "index.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "build": "NODE_OPTIONS=\"--max-old-space-size=7168\" webpack -c webpack.config.js"
+    "build": "NODE_OPTIONS=\"--max-old-space-size=7168\" webpack -c webpack.config.cjs"
   },
+  "type": "module",
   "keywords": [],
   "devDependencies": {
     "@babel/plugin-syntax-dynamic-import": "7.8.3",

tools/client-plugins/browser-scripts/python-worker.ts

@@ -1,5 +1,10 @@
 // We have to specify pyodide.js because we need to import that file (not .mjs)
-// and 'import' defaults to .mjs
+// and 'import' defaults to .mjs.
+
+// This is to do with how webpack handles node fallbacks - it uses the node
+// resolution algorithm to find the file, but that requires the full file name.
+// We can't add the extension, because it's in a bundle we're importing. However
+// we can import the .js file and then the strictness does not apply.
 import { loadPyodide, type PyodideInterface } from 'pyodide/pyodide.js';
 import pkg from 'pyodide/package.json';
 import type { PyProxy, PythonError } from 'pyodide/ffi';

tools/client-plugins/browser-scripts/tsconfig.json

@@ -1,13 +1,17 @@
 {
   "compilerOptions": {
     "target": "es2022",
-    "module": "CommonJS",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
     "lib": ["WebWorker", "DOM"],
     "allowJs": true,
     "strict": true,
     "forceConsistentCasingInFileNames": true,
     "esModuleInterop": true,
     "resolveJsonModule": true,
-    "noEmit": true
+    "noEmit": true,
+    "paths": {
+      "pyodide/ffi": ["./node_modules/pyodide/ffi.d.ts"] // Remove after updating pyodide (later versions correctly export ffi)
+    }
   }
 }

tools/client-plugins/browser-scripts/typescript-worker.ts

@@ -13,9 +13,6 @@ declare const ts: typeof import('typescript');
 const ctx: Worker & typeof globalThis = self as unknown as Worker &
   typeof globalThis;
 
-let tsEnv: VirtualTypeScriptEnvironment | null = null;
-let compilerHost: CompilerHost | null = null;
-
 interface TSCompileEvent extends MessageEvent {
   data: {
     type: 'compile';
@@ -29,9 +26,9 @@ interface TSCompiledMessage {
   error: string;
 }
 
-interface InitRequestEvent extends MessageEvent {
+interface CheckIsReadyRequestEvent extends MessageEvent {
   data: {
-    type: 'init';
+    type: 'check-is-ready';
   };
 }
 
@@ -42,15 +39,23 @@ interface CancelEvent extends MessageEvent {
   };
 }
 
+const TS_VERSION = '5'; // hardcoding for now, in the future this may be dynamic
+
+let tsEnv: VirtualTypeScriptEnvironment | null = null;
+let compilerHost: CompilerHost | null = null;
 let cachedVersion: string | null = null;
 
-async function setupTypeScript(version: string) {
-  // TODO: make sure no racing happens if multiple inits arrive at once.
-  if (cachedVersion == version) return tsEnv;
+// NOTE: vfs.globals must only be imported once, otherwise it will throw.
+importScripts('https://unpkg.com/@typescript/vfs@1.6.0/dist/vfs.globals.js');
 
+function importTS(version: string) {
+  if (cachedVersion == version) return;
   importScripts('https://unpkg.com/typescript@' + version);
-  importScripts('https://unpkg.com/@typescript/vfs@1.6.0/dist/vfs.globals.js');
+  cachedVersion = version;
+}
 
+async function setupTypeScript() {
+  importTS(TS_VERSION);
   const compilerOptions: CompilerOptions = {
     target: ts.ScriptTarget.ES2015,
     skipLibCheck: true // TODO: look into why this is needed. Are we doing something wrong? Could it be that it's not "synced"  with this TS version?
@@ -87,20 +92,15 @@ async function setupTypeScript(version: string) {
   // We freeze this to prevent learners from getting the worker into a
   // weird state.
   Object.freeze(self);
-
-  cachedVersion = version;
   return env;
 }
 
-// TODO: figure out how to start setting up TS in the background, but allow the
-// client to wait for it to be ready. Currently the waiting works, but the setup
-// is done on demand.
-// void setupTypeScript('5');
-
-ctx.onmessage = (e: TSCompileEvent | InitRequestEvent | CancelEvent) => {
+ctx.onmessage = (
+  e: TSCompileEvent | CheckIsReadyRequestEvent | CancelEvent
+) => {
   const { data, ports } = e;
-  if (data.type === 'init') {
-    void handleInitRequest(ports[0]);
+  if (data.type === 'check-is-ready') {
+    void handleCheckIsReadyRequest(ports[0]);
   } else if (data.type === 'cancel') {
     handleCancelRequest(data);
   } else {
@@ -108,13 +108,15 @@ ctx.onmessage = (e: TSCompileEvent | InitRequestEvent | CancelEvent) => {
   }
 };
 
+const isTSSetup = setupTypeScript();
+
 // This lets the client know that there is nothing to cancel.
 function handleCancelRequest({ value }: { value: number }) {
   postMessage({ type: 'is-alive', text: value });
 }
 
-async function handleInitRequest(port: MessagePort) {
-  await setupTypeScript('5');
+async function handleCheckIsReadyRequest(port: MessagePort) {
+  await isTSSetup;
   port.postMessage({ type: 'ready' });
 }
 

tools/client-plugins/browser-scripts/utils/format.js

@@ -1,7 +1,7 @@
 // TODO: this is a straight up copy of the format function from the client.
 // Figure out a way to share it.
 
-import { inspect } from 'util/util';
+import { inspect } from 'util/util.js';
 
 export function format(x) {
   // we're trying to mimic console.log, so we avoid wrapping strings in quotes:

tools/client-plugins/browser-scripts/webpack.config.cjs

@@ -84,7 +84,7 @@ module.exports = (env = {}) => {
     resolve: {
       fallback: {
         buffer: require.resolve('buffer'),
-        util: false,
+        util: require.resolve('util'),
         stream: false,
         process: require.resolve('process/browser.js')
       },