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().

Author: Bartek Wrona

src/lib/libatomic.js

@@ -154,9 +154,12 @@ addToLibrary({
 
   emscripten_has_threading_support: () => !!globalThis.SharedArrayBuffer,
 
+#if ENVIRONMENT_MAY_BE_NODE
+  emscripten_num_logical_cores__deps: ['$nodeOs'],
+#endif
   emscripten_num_logical_cores: () =>
 #if ENVIRONMENT_MAY_BE_NODE
-    ENVIRONMENT_IS_NODE ? require('node:os').cpus().length :
+    ENVIRONMENT_IS_NODE ? nodeOs.cpus().length :
 #endif
     navigator['hardwareConcurrency'],
 

src/lib/libcore.js

@@ -372,6 +372,11 @@ addToLibrary({
   },
 #endif
 
+#if ENVIRONMENT_MAY_BE_NODE
+  $nodeOs: "ENVIRONMENT_IS_NODE ? {{{ makeNodeImport('node:os') }}} : undefined",
+  $nodeChildProcess: "ENVIRONMENT_IS_NODE ? {{{ makeNodeImport('node:child_process') }}} : undefined",
+  _emscripten_system__deps: ['$nodeChildProcess'],
+#endif
   _emscripten_system: (command) => {
 #if ENVIRONMENT_MAY_BE_NODE
     if (ENVIRONMENT_IS_NODE) {

src/lib/libnodepath.js

@@ -12,7 +12,7 @@
 // operations. Hence, using `nodePath` should be safe here.
 
 addToLibrary({
-  $nodePath: "require('node:path')",
+  $nodePath: "{{{ makeNodeImport('node:path') }}}",
   $PATH__deps: ['$nodePath'],
   $PATH: `{
     isAbs: nodePath.isAbsolute,

src/lib/libsockfs.js

@@ -5,10 +5,17 @@
  */
 
 addToLibrary({
+  $SOCKFS__deps: ['$FS'],
   $SOCKFS__postset: () => {
+#if ENVIRONMENT_MAY_BE_NODE && EXPORT_ES6
+    // In ESM mode, pre-load 'ws' at init time since require() is not available.
+    // This runs lazily (only when SOCKFS is used, not at module load time).
+    addAtInit(`if (ENVIRONMENT_IS_NODE) {
+      SOCKFS.websocketModule = (await import('ws')).default;
+    }`);
+#endif
     addAtInit('SOCKFS.root = FS.mount(SOCKFS, {}, null);');
   },
-  $SOCKFS__deps: ['$FS'],
   $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)} */(SOCKFS.websocketModule);
+#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 = SOCKFS.websocketModule.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

@@ -569,14 +569,21 @@ var WasiLibrary = {
 
   // random.h
 
-#if ENVIRONMENT_MAY_BE_SHELL
+#if ENVIRONMENT_MAY_BE_NODE && MIN_NODE_VERSION < 190000
+  $nodeCrypto: "ENVIRONMENT_IS_NODE ? {{{ makeNodeImport('node:crypto') }}} : undefined",
+#endif
+
+#if ENVIRONMENT_MAY_BE_SHELL && ENVIRONMENT_MAY_BE_NODE && MIN_NODE_VERSION < 190000
+  $initRandomFill__deps: ['$base64Decode', '$nodeCrypto'],
+#elif ENVIRONMENT_MAY_BE_SHELL
   $initRandomFill__deps: ['$base64Decode'],
+#elif 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) {
-      var nodeCrypto = require('node:crypto');
       return (view) => nodeCrypto.randomFillSync(view);
     }
 #endif // ENVIRONMENT_MAY_BE_NODE

src/lib/libwasm_worker.js

@@ -288,9 +288,12 @@ if (ENVIRONMENT_IS_WASM_WORKER
     _wasmWorkers[id].postMessage({'_wsc': funcPtr, 'x': readEmAsmArgs(sigPtr, varargs) });
   },
 
+#if ENVIRONMENT_MAY_BE_NODE
+  emscripten_navigator_hardware_concurrency__deps: ['$nodeOs'],
+#endif
   emscripten_navigator_hardware_concurrency: () => {
 #if ENVIRONMENT_MAY_BE_NODE
-    if (ENVIRONMENT_IS_NODE) return require('node:os').cpus().length;
+    if (ENVIRONMENT_IS_NODE) return nodeOs.cpus().length;
 #endif
     return navigator['hardwareConcurrency'];
   },