Use library aliases for FS_<symbol> functions. (#24116)

Removes the custom code for exporting the FS_<symbol> with
EXPORTED_RUNTIME_FUNCTIONS. Using library symbols makes these exports
behave like all the other library exports.

Author: brendandahl

src/lib/libfs.js

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: MIT
  */
 
-addToLibrary({
+var LibraryFS = {
   $FS__deps: ['$randomFill', '$PATH', '$PATH_FS', '$TTY', '$MEMFS',
     '$FS_createPreloadedFile',
     '$FS_modeStringToFlags',
@@ -38,9 +38,7 @@ addToLibrary({
     addAtExit('FS.quit();');
     return `
 FS.createPreloadedFile = FS_createPreloadedFile;
-FS.staticInit();
-// Set module methods based on EXPORTED_RUNTIME_METHODS
-{{{ EXPORTED_RUNTIME_METHODS.filter((func) => func.startsWith('FS_')).map((func) => "Module['" + func + "'] = FS." + func.slice(3) + ";\n").reduce((str, func) => str + func, '') }}}`;
+FS.staticInit();`;
   },
   $FS: {
     root: null,
@@ -1917,22 +1915,23 @@ FS.staticInit();
 #endif
   },
 
-  $FS_createDataFile__deps: ['$FS'],
-  $FS_createDataFile: (parent, name, fileData, canRead, canWrite, canOwn) => {
-    FS.createDataFile(parent, name, fileData, canRead, canWrite, canOwn);
-  },
-
-  $FS_unlink__deps: ['$FS'],
-  $FS_unlink: (path) => FS.unlink(path),
-
   $FS_mkdirTree__docs: `
   /**
    * @param {number=} mode Optionally, the mode to create in. Uses mkdir's
    *                       default if not set.
    */`,
-  $FS_mkdirTree__deps: ['$FS'],
-  $FS_mkdirTree: (path, mode) => FS.mkdirTree(path, mode),
-
-  $FS_createLazyFile__deps: ['$FS'],
-  $FS_createLazyFile: 'FS.createLazyFile',
-});
+   $FS_mkdirTree__deps: ['$FS'],
+   $FS_mkdirTree: (path, mode) => FS.mkdirTree(path, mode),
+};
+
+// Add library aliases for all the FS.<symbol> as FS_<symbol>.
+for (let key in LibraryFS.$FS) {
+  const alias = `$FS_${key}`;
+  // Skip defining the alias if it already exists or if it's not an API function.
+  if (LibraryFS[alias] || key[0] !== key[0].toLowerCase()) {
+    continue;
+  }
+  LibraryFS[alias] = `(...args) => FS.${key}(...args)`;
+  LibraryFS[`${alias}__deps`] = ['$FS'];
+}
+addToLibrary(LibraryFS);

test/other/codesize/test_codesize_hello_O0.gzsize

@@ -1 +1 @@
-7785
+8292

test/other/codesize/test_codesize_hello_O0.jssize

@@ -1 +1 @@
-20761
+22165

test/other/codesize/test_codesize_minimal_O0.gzsize

@@ -1 +1 @@
-6099
+6595

test/other/codesize/test_codesize_minimal_O0.jssize

@@ -1 +1 @@
-16143
+17534

test/other/embind_tsgen_ignore_1.d.ts

@@ -1,11 +1,11 @@
 // TypeScript bindings for emscripten-generated code.  Automatically generated at compile time.
 declare namespace RuntimeExports {
-    let FS_createPath: any;
-    function FS_createDataFile(parent: any, name: any, fileData: any, canRead: any, canWrite: any, canOwn: any): void;
+    function FS_createPath(...args: any[]): any;
+    function FS_createDataFile(...args: any[]): any;
     function FS_createPreloadedFile(parent: any, name: any, url: any, canRead: any, canWrite: any, onload: any, onerror: any, dontCreateFile: any, canOwn: any, preFinish: any): void;
-    function FS_unlink(path: any): any;
-    let FS_createLazyFile: any;
-    let FS_createDevice: any;
+    function FS_unlink(...args: any[]): any;
+    function FS_createLazyFile(...args: any[]): any;
+    function FS_createDevice(...args: any[]): any;
     let addRunDependency: any;
     let removeRunDependency: any;
 }

test/other/test_unoptimized_code_size.js.size

@@ -1 +1 @@
-51593
+53547

test/other/test_unoptimized_code_size_strict.js.size

@@ -1 +1 @@
-49661
+51597

test/test_other.py

@@ -4145,8 +4145,7 @@ def test_exported_runtime_methods(self):
 
     # Check that the Module.FS_writeFile is not exported
     out = self.run_js('index.js', assert_returncode=NON_ZERO)
-    self.assertContained('undefined', out),
-    self.assertContained("Aborted('wasmExports' was not exported. add it to EXPORTED_RUNTIME_METHODS", out)
+    self.assertContained("Aborted('FS_writeFile' was not exported. add it to EXPORTED_RUNTIME_METHODS", out)
 
   def test_exported_runtime_methods_from_js_library(self):
     create_file('pre.js', '''