"Annotate" exported object to fix named / namespace imports of our API in Node ESM (#57133)

Author: jakebailey

Herebyfile.mjs

@@ -2,6 +2,7 @@
 import {
     CancelToken,
 } from "@esfx/canceltoken";
+import assert from "assert";
 import chalk from "chalk";
 import chokidar from "chokidar";
 import esbuild from "esbuild";
@@ -46,7 +47,7 @@ import {
 void 0;
 
 const copyrightFilename = "./scripts/CopyrightNotice.txt";
-const copyright = memoize(async () => {
+const getCopyrightHeader = memoize(async () => {
     const contents = await fs.promises.readFile(copyrightFilename, "utf-8");
     return contents.replace(/\r\n/g, "\n");
 });
@@ -76,7 +77,7 @@ export const generateLibs = task({
     run: async () => {
         await fs.promises.mkdir("./built/local", { recursive: true });
         for (const lib of libs()) {
-            let output = await copyright();
+            let output = await getCopyrightHeader();
 
             for (const source of lib.sources) {
                 const contents = await fs.promises.readFile(source, "utf-8");
@@ -187,10 +188,13 @@ async function runDtsBundler(entrypoint, output) {
  */
 function createBundler(entrypoint, outfile, taskOptions = {}) {
     const getOptions = memoize(async () => {
+        const copyright = await getCopyrightHeader();
+        const banner = taskOptions.exportIsTsObject ? "var ts = {}; ((module) => {" : "";
+
         /** @type {esbuild.BuildOptions} */
         const options = {
             entryPoints: [entrypoint],
-            banner: { js: await copyright() },
+            banner: { js: copyright + banner },
             bundle: true,
             outfile,
             platform: "node",
@@ -205,12 +209,10 @@ function createBundler(entrypoint, outfile, taskOptions = {}) {
         };
 
         if (taskOptions.exportIsTsObject) {
-            // We use an IIFE so we can inject the footer, and so that "ts" is global if not loaded as a module.
-            options.format = "iife";
-            // Name the variable ts, matching our old big bundle and so we can use the code below.
-            options.globalName = "ts";
-            // If we are in a CJS context, export the ts namespace.
-            options.footer = { js: `\nif (typeof module !== "undefined" && module.exports) { module.exports = ts; }` };
+            // Monaco bundles us as ESM by wrapping our code with something that defines module.exports
+            // but then does not use it, instead using the `ts` variable. Ensure that if we think we're CJS
+            // that we still set `ts` to the module.exports object.
+            options.footer = { js: `})(typeof module !== "undefined" && module.exports ? module : { exports: ts });\nif (typeof module !== "undefined" && module.exports) { ts = module.exports; }` };
 
             // esbuild converts calls to "require" to "__require"; this function
             // calls the real require if it exists, or throws if it does not (rather than
@@ -227,13 +229,25 @@ function createBundler(entrypoint, outfile, taskOptions = {}) {
             const fakeName = "Q".repeat(require.length);
             const fakeNameRegExp = new RegExp(fakeName, "g");
             options.define = { [require]: fakeName };
+
+            // For historical reasons, TypeScript does not set __esModule. Hack esbuild's __toCommonJS to be a noop.
+            // We reference `__copyProps` to ensure the final bundle doesn't have any unreferenced code.
+            const toCommonJsRegExp = /var __toCommonJS .*/;
+            const toCommonJsRegExpReplacement = "var __toCommonJS = (mod) => (__copyProps, mod); // Modified helper to skip setting __esModule.";
+
             options.plugins = [
                 {
-                    name: "fix-require",
+                    name: "post-process",
                     setup: build => {
                         build.onEnd(async () => {
                             let contents = await fs.promises.readFile(outfile, "utf-8");
                             contents = contents.replace(fakeNameRegExp, require);
+                            let matches = 0;
+                            contents = contents.replace(toCommonJsRegExp, () => {
+                                matches++;
+                                return toCommonJsRegExpReplacement;
+                            });
+                            assert(matches === 1, "Expected exactly one match for __toCommonJS");
                             await fs.promises.writeFile(outfile, contents);
                         });
                     },
@@ -450,7 +464,7 @@ export = ts;
  * @param {string} contents
  */
 async function fileContentsWithCopyright(contents) {
-    return await copyright() + contents.trim().replace(/\r\n/g, "\n") + "\n";
+    return await getCopyrightHeader() + contents.trim().replace(/\r\n/g, "\n") + "\n";
 }
 
 const lssl = task({

scripts/checkModuleFormat.mjs

@@ -5,31 +5,37 @@ import {
     __importDefault,
     __importStar,
 } from "tslib";
+import {
+    pathToFileURL,
+} from "url";
 
 // This script tests that TypeScript's CJS API is structured
 // as expected. It calls "require" as though it were in CWD,
 // so it can be tested on a separate install of TypeScript.
 
 const require = createRequire(process.cwd() + "/index.js");
+const typescript = process.argv[2];
+const resolvedTypeScript = pathToFileURL(require.resolve(typescript)).toString();
 
-console.log(`Testing ${process.argv[2]}...`);
-const ts = require(process.argv[2]);
+console.log(`Testing ${typescript}...`);
 
 // See: https://github.com/microsoft/TypeScript/pull/51474#issuecomment-1310871623
-/** @type {[fn: (() => any), shouldSucceed: boolean][]} */
+/** @type {[fn: (() => Promise<any>), shouldSucceed: boolean][]} */
 const fns = [
-    [() => ts.version, true],
-    [() => ts.default.version, false],
-    [() => __importDefault(ts).version, false],
-    [() => __importDefault(ts).default.version, true],
-    [() => __importStar(ts).version, true],
-    [() => __importStar(ts).default.version, true],
+    [() => require(typescript).version, true],
+    [() => require(typescript).default.version, false],
+    [() => __importDefault(require(typescript)).version, false],
+    [() => __importDefault(require(typescript)).default.version, true],
+    [() => __importStar(require(typescript)).version, true],
+    [() => __importStar(require(typescript)).default.version, true],
+    [async () => (await import(resolvedTypeScript)).version, true],
+    [async () => (await import(resolvedTypeScript)).default.version, true],
 ];
 
 for (const [fn, shouldSucceed] of fns) {
     let success = false;
     try {
-        success = !!fn();
+        success = !!(await fn());
     }
     catch {
         // Ignore
@@ -43,4 +49,10 @@ for (const [fn, shouldSucceed] of fns) {
         process.exitCode = 1;
     }
 }
-console.log("ok");
+
+if (process.exitCode) {
+    console.log("fail");
+}
+else {
+    console.log("ok");
+}

src/compiler/core.ts

@@ -2743,12 +2743,8 @@ export function skipWhile<T, U extends T>(array: readonly T[] | undefined, predi
 export function isNodeLikeSystem(): boolean {
     // This is defined here rather than in sys.ts to prevent a cycle from its
     // use in performanceCore.ts.
-    //
-    // We don't use the presence of `require` to check if we are in Node;
-    // when bundled using esbuild, this function will be rewritten to `__require`
-    // and definitely exist.
     return typeof process !== "undefined"
         && !!process.nextTick
         && !(process as any).browser
-        && typeof module === "object";
+        && typeof require !== "undefined";
 }

src/typescript/typescript.ts

@@ -2,7 +2,6 @@ import {
     Debug,
     LogLevel,
 } from "./_namespaces/ts";
-import * as ts from "./_namespaces/ts";
 
 // enable deprecation logging
 declare const console: any;
@@ -23,4 +22,4 @@ if (typeof console !== "undefined") {
     };
 }
 
-export = ts;
+export * from "./_namespaces/ts";