Replace require() with await import() in EXPORT_ES6 shell/runtime files

When EXPORT_ES6 is enabled, the generated JS used createRequire() to
polyfill require(), which breaks bundlers (webpack, Rollup, esbuild)
and Electron's renderer process. Since EXPORT_ES6 requires MODULARIZE,
the module body is wrapped in an async function where await is valid.

- shell.js: Remove createRequire block entirely. Use await import()
  for worker_threads, fs, path, url, util. Replace __dirname with
  import.meta.url for path resolution.
- shell_minimal.js: Same pattern for worker_threads and fs. Replace
  __dirname with new URL(..., import.meta.url) for wasm file loading.
- runtime_debug.js: Skip local require() for fs/util when EXPORT_ES6,
  reuse outer-scope variables from shell.js instead.
- runtime_common.js: Guard perf_hooks require() with EXPORT_ES6
  alternative.
- preamble.js: Hoist await import('node:v8') above instantiateSync()
  for NODE_CODE_CACHING since await can't be used inside sync functions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Bartek Wrona

src/preamble.js

@@ -549,13 +549,21 @@ var splitModuleProxyHandler = {
 };
 #endif
 
+#if NODE_CODE_CACHING && ENVIRONMENT_MAY_BE_NODE && EXPORT_ES6
+var nodeV8 = ENVIRONMENT_IS_NODE ? await import('node:v8') : undefined;
+#endif
+
 #if SPLIT_MODULE || !WASM_ASYNC_COMPILATION
 function instantiateSync(file, info) {
   var module;
   var binary = getBinarySync(file);
 #if NODE_CODE_CACHING
   if (ENVIRONMENT_IS_NODE) {
+#if EXPORT_ES6
+    var v8 = nodeV8;
+#else
     var v8 = require('node:v8');
+#endif
     // Include the V8 version in the cache name, so that we don't try to
     // load cached code from another version, which fails silently (it seems
     // to load ok, but we do actually recompile the binary every time).

src/runtime_common.js

@@ -171,7 +171,11 @@ if (ENVIRONMENT_IS_NODE) {
   // depends on it for accurate timing.
   // Use `global` rather than `globalThis` here since older versions of node
   // don't have `globalThis`.
+#if EXPORT_ES6
+  global.performance ??= (await import('perf_hooks')).performance;
+#else
   global.performance ??= require('perf_hooks').performance;
+#endif
 }
 #endif
 

src/runtime_debug.js

@@ -15,8 +15,10 @@ function dbg(...args) {
   // See https://github.com/emscripten-core/emscripten/issues/14804
   if (ENVIRONMENT_IS_NODE) {
     // TODO(sbc): Unify with err/out implementation in shell.sh.
+#if !EXPORT_ES6
     var fs = require('node:fs');
     var utils = require('node:util');
+#endif
     function stringify(a) {
       switch (typeof a) {
         case 'object': return utils.inspect(a);

src/shell.js

@@ -107,18 +107,13 @@ if (ENVIRONMENT_IS_PTHREAD) {
 #endif
 #endif
 
-#if ENVIRONMENT_MAY_BE_NODE && (EXPORT_ES6 || PTHREADS || WASM_WORKERS)
+#if ENVIRONMENT_MAY_BE_NODE && (PTHREADS || WASM_WORKERS)
 if (ENVIRONMENT_IS_NODE) {
 #if EXPORT_ES6
-  // When building an ES module `require` is not normally available.
-  // We need to use `createRequire()` to construct the require()` function.
-  const { createRequire } = await import('node:module');
-  /** @suppress{duplicate} */
-  var require = createRequire(import.meta.url);
-#endif
-
-#if PTHREADS || WASM_WORKERS
+  var worker_threads = await import('node:worker_threads');
+#else
   var worker_threads = require('node:worker_threads');
+#endif
   global.Worker = worker_threads.Worker;
   ENVIRONMENT_IS_WORKER = !worker_threads.isMainThread;
 #if PTHREADS
@@ -129,7 +124,6 @@ if (ENVIRONMENT_IS_NODE) {
 #if WASM_WORKERS
   ENVIRONMENT_IS_WASM_WORKER = ENVIRONMENT_IS_WORKER && worker_threads.workerData == 'em-ww'
 #endif
-#endif // PTHREADS || WASM_WORKERS
 }
 #endif // ENVIRONMENT_MAY_BE_NODE
 
@@ -200,11 +194,17 @@ if (ENVIRONMENT_IS_NODE) {
 
   // These modules will usually be used on Node.js. Load them eagerly to avoid
   // the complexity of lazy-loading.
+#if EXPORT_ES6
+  var fs = await import('node:fs');
+#else
   var fs = require('node:fs');
+#endif
 
 #if EXPORT_ES6
   if (_scriptName.startsWith('file:')) {
-    scriptDirectory = require('node:path').dirname(require('node:url').fileURLToPath(_scriptName)) + '/';
+    var nodePath = await import('node:path');
+    var nodeUrl = await import('node:url');
+    scriptDirectory = nodePath.dirname(nodeUrl.fileURLToPath(_scriptName)) + '/';
   }
 #else
   scriptDirectory = __dirname + '/';
@@ -352,7 +352,11 @@ if (!ENVIRONMENT_IS_AUDIO_WORKLET)
 var defaultPrint = console.log.bind(console);
 var defaultPrintErr = console.error.bind(console);
 if (ENVIRONMENT_IS_NODE) {
+#if EXPORT_ES6
+  var utils = await import('node:util');
+#else
   var utils = require('node:util');
+#endif
   var stringify = (a) => typeof a == 'object' ? utils.inspect(a) : a;
   defaultPrint = (...args) => fs.writeSync(1, args.map(stringify).join(' ') + '\n');
   defaultPrintErr = (...args) => fs.writeSync(2, args.map(stringify).join(' ') + '\n');

src/shell_minimal.js

@@ -55,7 +55,11 @@ var ENVIRONMENT_IS_WEB = !ENVIRONMENT_IS_NODE;
 
 #if ENVIRONMENT_MAY_BE_NODE && (PTHREADS || WASM_WORKERS)
 if (ENVIRONMENT_IS_NODE) {
+#if EXPORT_ES6
+  var worker_threads = await import('node:worker_threads');
+#else
   var worker_threads = require('node:worker_threads');
+#endif
   global.Worker = worker_threads.Worker;
 }
 #endif
@@ -99,7 +103,11 @@ if (ENVIRONMENT_IS_NODE && ENVIRONMENT_IS_SHELL) {
 var defaultPrint = console.log.bind(console);
 var defaultPrintErr = console.error.bind(console);
 if (ENVIRONMENT_IS_NODE) {
+#if EXPORT_ES6
+  var fs = await import('node:fs');
+#else
   var fs = require('node:fs');
+#endif
   defaultPrint = (...args) => fs.writeSync(1, args.join(' ') + '\n');
   defaultPrintErr = (...args) => fs.writeSync(2, args.join(' ') + '\n');
 }
@@ -181,6 +189,17 @@ if (!ENVIRONMENT_IS_PTHREAD) {
 // Wasm or Wasm2JS loading:
 
 if (ENVIRONMENT_IS_NODE) {
+#if EXPORT_ES6
+  var fs = await import('node:fs');
+#if WASM == 2
+  if (globalThis.WebAssembly) Module['wasm'] = fs.readFileSync(new URL('{{{ TARGET_BASENAME }}}.wasm', import.meta.url));
+  else eval(fs.readFileSync(new URL('{{{ TARGET_BASENAME }}}.wasm.js', import.meta.url))+'');
+#else
+#if !WASM2JS
+  Module['wasm'] = fs.readFileSync(new URL('{{{ TARGET_BASENAME }}}.wasm', import.meta.url));
+#endif
+#endif
+#else
   var fs = require('node:fs');
 #if WASM == 2
   if (globalThis.WebAssembly) Module['wasm'] = fs.readFileSync(__dirname + '/{{{ TARGET_BASENAME }}}.wasm');
@@ -190,6 +209,7 @@ if (ENVIRONMENT_IS_NODE) {
   Module['wasm'] = fs.readFileSync(__dirname + '/{{{ TARGET_BASENAME }}}.wasm');
 #endif
 #endif
+#endif
 }
 #endif