Fix broken JS glue for AUDIO_WORKLETS with EXPORT_ES6

Building to WASM with AUDIO_WORKLETS and EXPORT_ES6 results in:

  test.js:989 Uncaught (in promise) TypeError: Cannot set property wasmTable of #<Object> which has only a getter
      at receiveInstance (test.js:989:25)
      at receiveInstantiationResult (test.js:1011:5)

The read-only getter at issue is created only when ASSERTIONS != 0;
however, ASSERTIONS defaults to 1. We therefore append wasmTable to
EXPORTED_RUNTIME_METHODS if necessary.

We also prevent an ES6 Audio Worklet from loading the .wasm binary
via `new URL()`, as `URL` is unavailable in AudioWorkletGlobalScope.

Author: kangtastic

src/preamble.js

@@ -608,14 +608,14 @@ function instrumentWasmTableWithAbort() {
 #endif
 
 var wasmBinaryFile;
-#if EXPORT_ES6 && USE_ES6_IMPORT_META && !SINGLE_FILE
+#if EXPORT_ES6 && USE_ES6_IMPORT_META && !SINGLE_FILE && !AUDIO_WORKLET // `URL` is undefined in Audio Worklet scope, so we cannot use `new URL()`.
 if (Module['locateFile']) {
 #endif
   wasmBinaryFile = '{{{ WASM_BINARY_FILE }}}';
   if (!isDataURI(wasmBinaryFile)) {
     wasmBinaryFile = locateFile(wasmBinaryFile);
   }
-#if EXPORT_ES6 && USE_ES6_IMPORT_META && !SINGLE_FILE // in single-file mode, repeating WASM_BINARY_FILE would emit the contents again
+#if EXPORT_ES6 && USE_ES6_IMPORT_META && !SINGLE_FILE && !AUDIO_WORKLET // In single-file mode, repeating WASM_BINARY_FILE would emit the contents again. For an Audio Worklet, we cannot use `new URL()`.
 } else {
 #if ENVIRONMENT_MAY_BE_SHELL
   if (ENVIRONMENT_IS_SHELL)
@@ -1001,7 +1001,7 @@ function createWasm() {
     assert(wasmTable, 'table not found in wasm exports');
 #endif
 
-#if AUDIO_WORKLET
+#if AUDIO_WORKLET && !(EXPORT_ES6 && ASSERTIONS)  // If EXPORT_ES6, we may have already done this.
     // If we are in the audio worklet environment, we can only access the Module object
     // and not the global scope of the main JS script. Therefore we need to export
     // all functions that the audio worklet scope needs onto the Module object.

test/test_browser.py

@@ -5759,6 +5759,8 @@ def test_full_js_library_strict(self):
     'pthreads_and_closure': (['-pthread', '--closure', '1', '-Oz'],),
     'minimal_runtime': (['-sMINIMAL_RUNTIME'],),
     'minimal_runtime_pthreads_and_closure': (['-sMINIMAL_RUNTIME', '-pthread', '--closure', '1', '-Oz'],),
+    'pthreads_es6': (['-pthread', '-sPTHREAD_POOL_SIZE=2', '-sEXPORT_ES6'],),
+    'es6': (['-sEXPORT_ES6'],),
   })
   def test_audio_worklet(self, args):
     if '-sMEMORY64' in args and is_firefox():

tools/link.py

@@ -1350,6 +1350,11 @@ def phase_linker_setup(options, state, newargs):
       # MINIMAL_RUNTIME exports these manually, since this export mechanism is placed
       # in global scope that is not suitable for MINIMAL_RUNTIME loader.
       settings.EXPORTED_RUNTIME_METHODS += ['stackSave', 'stackAlloc', 'stackRestore']
+      if settings.EXPORT_ES6 and settings.ASSERTIONS:
+        # With ASSERTIONS, EXPORT_ES6 assigns a read-only getter that prevents assigning
+        # Module['wasmTable'], which will then prevent the Audio Worklet from loading.
+        settings.EXPORTED_RUNTIME_METHODS += ['wasmTable']
+
 
   if settings.FORCE_FILESYSTEM and not settings.MINIMAL_RUNTIME:
     # when the filesystem is forced, we export by default methods that filesystem usage