Fix Closure await import mangling regression

src/parseTools.mjs

@@ -47,9 +47,6 @@ function mangleUnsupportedSyntax(text) {
     // placeholders during preprocess phase, and back after all the other ops.
     // See also: `fix_js_mangling` in link.py.
     // FIXME: Remove after https://github.com/google/closure-compiler/issues/3835 is fixed.
-    if (EXPORT_ES6) {
-      text = text.replaceAll('await import', 'EMSCRIPTEN$AWAIT$IMPORT');
-    }
     text = text.replaceAll('await createWasm()', 'EMSCRIPTEN$AWAIT(createWasm())');
     text = text.replaceAll('await run()', 'EMSCRIPTEN$AWAIT(run())');
     text = text.replaceAll('await instantiatePromise', 'EMSCRIPTEN$AWAIT(instantiatePromise)');
@@ -102,6 +99,15 @@ export function preprocess(filename) {
   let text = readFile(filename);
   // Remove windows line endings, if any
   text = text.replace(/\r\n/g, '\n');
+  if (EXPORT_ES6 && USE_CLOSURE_COMPILER) {
+    // Replace `await import` with a placeholder during preprocessing, and restore
+    // it after other transforms. This must be done in `preprocess` (rather than
+    // `mangleUnsupportedSyntax`) to avoid accidentally rewriting `await import`
+    // inside `nodePthreadDetection()` and `nodeWWDetection()` macro expansions.
+    // See also: `fix_js_mangling` in link.py.
+    // FIXME: Remove after https://github.com/google/closure-compiler/issues/3835 is fixed.
+    text = text.replaceAll('await import', 'EMSCRIPTEN$AWAIT$IMPORT');
+  }
 
   const IGNORE = 0;
   const SHOW = 1;

test/test_other.py

@@ -468,6 +468,19 @@ def test_esm_worker_single_file(self):
     self.assertContained("new Worker(new URL('hello_world.mjs', import.meta.url), {", src)
     self.assertContained('Hello, world!', self.run_js('hello_world.mjs'))
 
+  def test_esm_worker_closure(self):
+    self.run_process([EMCC, '-o', 'hello_world.mjs',
+                      '-sEXIT_RUNTIME', '-sPROXY_TO_PTHREAD', '-pthread', '-O2',
+                      test_file('hello_world.c'), '--closure=1'])
+    src = read_file('hello_world.mjs')
+    self.assertContained('new URL("hello_world.wasm",import.meta.url)', src)
+    self.assertContained('(await import("node:worker_threads")).workerData==="em-pthread"', src)
+    create_file('run.mjs', '''
+    import Module from './hello_world.mjs';
+    await Module();
+    ''')
+    self.assertContained('Hello, world!', self.run_js('run.mjs'))
+
   def test_esm_closure(self):
     self.run_process([EMCC, '-o', 'hello_world.mjs',
                       '--extern-post-js', test_file('modularize_post_js.js'),

tools/link.py

@@ -2111,7 +2111,7 @@ def phase_source_transforms(options):
 
 # Unmangle previously mangled `await import` and `await` references in
 # both main code and libraries.
-# See also: `mangleUnsupportedSyntax` in parseTools.mjs.
+# See also: `mangleUnsupportedSyntax` and `preprocess` in parseTools.mjs.
 def fix_js_mangling(js_file):
   # Mangling only takes place under closure in MODULARIZE mode.
   if not settings.MODULARIZE or not settings.USE_CLOSURE_COMPILER: