Replace require() with library symbols in EXPORT_ES6 library files

Library functions run in synchronous context where await is unavailable.
Define top-level library symbols that use await import() at module init
time, then reference them via __deps from synchronous functions.

- Add libnode_imports.js with shared $nodeOs symbol, register in
  modules.mjs when EXPORT_ES6 is enabled.
- libatomic.js, libwasm_worker.js: Use $nodeOs for os.cpus().length
  instead of require('node:os').
- libwasi.js: Define $nodeCrypto for crypto.randomFillSync in
  $initRandomFill. Combine conditional __deps to avoid override.
- libcore.js: Define $nodeChildProcess for _emscripten_system.
- libnodepath.js: Switch $nodePath initializer to await import().
- libsockfs.js: Define $nodeWs ((await import('ws')).default) for
  WebSocket constructor in connect() and Server in listen().

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

Author: Bartek Wrona

src/lib/libatomic.js

@@ -159,9 +159,16 @@ addToLibrary({
 
   emscripten_has_threading_support: () => !!globalThis.SharedArrayBuffer,
 
+#if EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE
+  emscripten_num_logical_cores__deps: ['$nodeOs'],
+#endif
   emscripten_num_logical_cores: () =>
 #if ENVIRONMENT_MAY_BE_NODE
+#if EXPORT_ES6
+    ENVIRONMENT_IS_NODE ? nodeOs.cpus().length :
+#else
     ENVIRONMENT_IS_NODE ? require('node:os').cpus().length :
+#endif
 #endif
     navigator['hardwareConcurrency'],
 });

src/lib/libcore.js

@@ -343,6 +343,10 @@ addToLibrary({
   },
 #endif
 
+#if EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE
+  $nodeChildProcess: "ENVIRONMENT_IS_NODE ? await import('node:child_process') : undefined",
+  _emscripten_system__deps: ['$nodeChildProcess'],
+#endif
   _emscripten_system: (command) => {
 #if ENVIRONMENT_MAY_BE_NODE
     if (ENVIRONMENT_IS_NODE) {
@@ -351,7 +355,11 @@ addToLibrary({
       var cmdstr = UTF8ToString(command);
       if (!cmdstr.length) return 0; // this is what glibc seems to do (shell works test?)
 
+#if EXPORT_ES6
+      var cp = nodeChildProcess;
+#else
       var cp = require('node:child_process');
+#endif
       var ret = cp.spawnSync(cmdstr, [], {shell:true, stdio:'inherit'});
 
       var _W_EXITCODE = (ret, sig) => ((ret) << 8 | (sig));

src/lib/libnode_imports.js

@@ -0,0 +1,16 @@
+/**
+ * @license
+ * Copyright 2025 The Emscripten Authors
+ * SPDX-License-Identifier: MIT
+ */
+
+// Shared Node.js module imports for use by library functions when EXPORT_ES6
+// is enabled. These are initialized at module top level (async context) so
+// they can use `await import()`, and then referenced by synchronous library
+// functions via __deps.
+
+#if EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE
+addToLibrary({
+  $nodeOs: "ENVIRONMENT_IS_NODE ? await import('node:os') : undefined",
+});
+#endif

src/lib/libnodepath.js

@@ -12,7 +12,11 @@
 // operations. Hence, using `nodePath` should be safe here.
 
 addToLibrary({
+#if EXPORT_ES6
+  $nodePath: "await import('node:path')",
+#else
   $nodePath: "require('node:path')",
+#endif
   $PATH__deps: ['$nodePath'],
   $PATH: `{
     isAbs: nodePath.isAbsolute,

src/lib/libsockfs.js

@@ -5,10 +5,17 @@
  */
 
 addToLibrary({
+#if EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE
+  $nodeWs: "ENVIRONMENT_IS_NODE ? (await import('ws')).default : undefined",
+#endif
   $SOCKFS__postset: () => {
     addAtInit('SOCKFS.root = FS.mount(SOCKFS, {}, null);');
   },
+#if EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE
+  $SOCKFS__deps: ['$FS', '$nodeWs'],
+#else
   $SOCKFS__deps: ['$FS'],
+#endif
   $SOCKFS: {
 #if expectToReceiveOnModule('websocket')
     websocketArgs: {},
@@ -216,7 +223,11 @@ addToLibrary({
             var WebSocketConstructor;
 #if ENVIRONMENT_MAY_BE_NODE
             if (ENVIRONMENT_IS_NODE) {
+#if EXPORT_ES6
+              WebSocketConstructor = /** @type{(typeof WebSocket)} */(nodeWs);
+#else
               WebSocketConstructor = /** @type{(typeof WebSocket)} */(require('ws'));
+#endif
             } else
 #endif // ENVIRONMENT_MAY_BE_NODE
             {
@@ -522,7 +533,11 @@ addToLibrary({
         if (sock.server) {
            throw new FS.ErrnoError({{{ cDefs.EINVAL }}});  // already listening
         }
+#if EXPORT_ES6
+        var WebSocketServer = nodeWs.Server;
+#else
         var WebSocketServer = require('ws').Server;
+#endif
         var host = sock.saddr;
 #if SOCKET_DEBUG
         dbg(`websocket: listen: ${host}:${sock.sport}`);

src/lib/libwasi.js

@@ -569,15 +569,27 @@ var WasiLibrary = {
 
   // random.h
 
-#if ENVIRONMENT_MAY_BE_SHELL
+#if EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE && MIN_NODE_VERSION < 190000
+  $nodeCrypto: "ENVIRONMENT_IS_NODE ? await import('node:crypto') : undefined",
+#endif
+
+#if ENVIRONMENT_MAY_BE_SHELL && EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE && MIN_NODE_VERSION < 190000
+  $initRandomFill__deps: ['$base64Decode', '$nodeCrypto'],
+#elif ENVIRONMENT_MAY_BE_SHELL
   $initRandomFill__deps: ['$base64Decode'],
+#elif EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE && MIN_NODE_VERSION < 190000
+  $initRandomFill__deps: ['$nodeCrypto'],
 #endif
   $initRandomFill: () => {
 #if ENVIRONMENT_MAY_BE_NODE && MIN_NODE_VERSION < 190000
     // This block is not needed on v19+ since crypto.getRandomValues is builtin
     if (ENVIRONMENT_IS_NODE) {
+#if EXPORT_ES6
+      return (view) => nodeCrypto.randomFillSync(view);
+#else
       var nodeCrypto = require('node:crypto');
       return (view) => nodeCrypto.randomFillSync(view);
+#endif
     }
 #endif // ENVIRONMENT_MAY_BE_NODE
 

src/lib/libwasm_worker.js

@@ -289,9 +289,16 @@ if (ENVIRONMENT_IS_WASM_WORKER
     _wasmWorkers[id].postMessage({'_wsc': funcPtr, 'x': readEmAsmArgs(sigPtr, varargs) });
   },
 
+#if EXPORT_ES6 && ENVIRONMENT_MAY_BE_NODE
+  emscripten_navigator_hardware_concurrency__deps: ['$nodeOs'],
+#endif
   emscripten_navigator_hardware_concurrency: () => {
 #if ENVIRONMENT_MAY_BE_NODE
+#if EXPORT_ES6
+    if (ENVIRONMENT_IS_NODE) return nodeOs.cpus().length;
+#else
     if (ENVIRONMENT_IS_NODE) return require('node:os').cpus().length;
+#endif
 #endif
     return navigator['hardwareConcurrency'];
   },

src/modules.mjs

@@ -166,6 +166,10 @@ function calculateLibraries() {
     libraries.push('libatomic.js');
   }
 
+  if (EXPORT_ES6) {
+    libraries.push('libnode_imports.js');
+  }
+
   if (MAX_WEBGL_VERSION >= 2) {
     // libwebgl2.js must be included only after libwebgl.js, so if we are
     // about to include libwebgl2.js, first squeeze in libwebgl.js.