Avoid importing Node's modules on demand

Remove `requireNodeFS()` in favor of always importing these Node
modules.

These `require()`'s will always be used on Node.js, except when
linking with `-sSINGLE_FILE`. But in that case, `stdin` usage,
or using the `-sMAIN_MODULE` and/or `-sNODERAWFS` options would
still depend on these imports.

Author: kleisauke

src/library_nodefs.js

@@ -6,7 +6,7 @@
 
 mergeInto(LibraryManager.library, {
   $NODEFS__deps: ['$FS', '$PATH', '$ERRNO_CODES', '$mmapAlloc'],
-  $NODEFS__postset: 'if (ENVIRONMENT_IS_NODE) { requireNodeFS(); NODEFS.staticInit(); }',
+  $NODEFS__postset: 'if (ENVIRONMENT_IS_NODE) { NODEFS.staticInit(); }',
   $NODEFS: {
     isWindows: false,
     staticInit: () => {

src/node_shell_read.js

@@ -4,18 +4,9 @@
  * SPDX-License-Identifier: MIT
  */
 
-var fs;
-var nodePath;
-
-var requireNodeFS = () => {
-  // Use nodePath as the indicator for these not being initialized,
-  // since in some environments a global fs may have already been
-  // created.
-  if (!nodePath) {
-    fs = require('fs');
-    nodePath = require('path');
-  }
-};
+// These modules will usually be used on Node.js.
+var fs = require('fs');
+var nodePath = require('path');
 
 read_ = (filename, binary) => {
 #if SUPPORT_BASE64_EMBEDDING
@@ -24,7 +15,6 @@ read_ = (filename, binary) => {
     return binary ? ret : ret.toString();
   }
 #endif
-  requireNodeFS();
   filename = nodePath['normalize'](filename);
   return fs.readFileSync(filename, binary ? undefined : 'utf8');
 };
@@ -47,7 +37,6 @@ readAsync = (filename, onload, onerror) => {
     onload(ret);
   }
 #endif
-  requireNodeFS();
   filename = nodePath['normalize'](filename);
   fs.readFile(filename, function(err, data) {
     if (err) onerror(err);

src/preamble.js

@@ -771,7 +771,6 @@ function instantiateSync(file, info) {
       // to load ok, but we do actually recompile the binary every time).
       var cachedCodeFile = '{{{ WASM_BINARY_FILE }}}.' + v8.cachedDataVersionTag() + '.cached';
       cachedCodeFile = locateFile(cachedCodeFile);
-      requireNodeFS();
       var hasCached = fs.existsSync(cachedCodeFile);
       if (hasCached) {
 #if RUNTIME_LOGGING

src/shell.js

@@ -258,7 +258,6 @@ if (ENVIRONMENT_IS_NODE) {
 #if WASM == 2
   // If target shell does not support Wasm, load the JS version of the code.
   if (typeof WebAssembly == 'undefined') {
-    requireNodeFS();
     eval(fs.readFileSync(locateFile('{{{ TARGET_BASENAME }}}.wasm.js'))+'');
   }
 #endif
@@ -423,7 +422,6 @@ if (ENVIRONMENT_IS_NODE) {
 var defaultPrint = console.log.bind(console);
 var defaultPrintErr = console.warn.bind(console);
 if (ENVIRONMENT_IS_NODE) {
-  requireNodeFS();
   defaultPrint = (str) => fs.writeSync(1, str + '\n');
   defaultPrintErr = (str) => fs.writeSync(2, str + '\n');
 }