[AUDIO_WORKLET] Wait for Wasm instance to start using audio worklet.

This fixes intermittent test failures where the AudioWorklet was used
before the Wasm module was loaded.

Author: brendandahl

src/audio_worklet.js

@@ -153,6 +153,8 @@ class BootstrapMessages extends AudioWorkletProcessor {
     messagePort = this.port;
     /** @suppress {checkTypes} */
     messagePort.onmessage = async (msg) => {
+      // Wait for the Wasm module to be instantiated.
+      await readyPromise;
       let d = msg.data;
       if (d['_wpn']) {
         // '_wpn' is short for 'Worklet Processor Node', using an identifier
@@ -170,6 +172,8 @@ class BootstrapMessages extends AudioWorkletProcessor {
         // conflict with user messages
         messagePort.postMessage({'_wsc': d.callback, args: [d.contextHandle, 1/*EM_TRUE*/, d.userData] });
       } else if (d['_wsc']) {
+        // Wait for the Wasm module to be instantiated.
+        await readyPromise;
         getWasmTableEntry(d['_wsc'])(...d.args);
       };
     }

src/lib/libcore.js

@@ -117,7 +117,7 @@ addToLibrary({
     // if exit() was called explicitly, warn the user if the runtime isn't actually being shut down
     if (keepRuntimeAlive() && !implicit) {
       var msg = `program exited (with status: ${status}), but keepRuntimeAlive() is set (counter=${runtimeKeepaliveCounter}) due to an async operation, so halting execution but not exiting the runtime or preventing further async execution (you can use emscripten_force_exit, if you want to force a true shutdown)`;
-#if MODULARIZE
+#if USE_READY_PROMISE
       readyPromiseReject?.(msg);
 #endif // MODULARIZE
       err(msg);

src/postamble.js

@@ -139,7 +139,7 @@ function run() {
 
 #if PTHREADS || WASM_WORKERS
   if ({{{ ENVIRONMENT_IS_WORKER_THREAD() }}}) {
-#if MODULARIZE
+#if USE_READY_PROMISE
     readyPromiseResolve?.(Module);
 #endif
     initRuntime();
@@ -179,7 +179,7 @@ function run() {
     preMain();
 #endif
 
-#if MODULARIZE
+#if USE_READY_PROMISE
     readyPromiseResolve?.(Module);
 #endif
 #if expectToReceiveOnModule('onRuntimeInitialized')

src/postamble_modularize.js

@@ -11,10 +11,7 @@ if (runtimeInitialized)  {
   moduleRtn = Module;
 } else {
   // Set up the promise that indicates the Module is initialized
-  moduleRtn = new Promise((resolve, reject) => {
-    readyPromiseResolve = resolve;
-    readyPromiseReject = reject;
-  });
+  moduleRtn = readyPromise = createReadyPromise();
 }
 #else
 moduleRtn = {};

src/preamble.js

@@ -363,7 +363,7 @@ function abort(what) {
   /** @suppress {checkTypes} */
   var e = new WebAssembly.RuntimeError(what);
 
-#if MODULARIZE
+#if USE_READY_PROMISE
   readyPromiseReject?.(e);
 #endif
   // Throw the error whether or not MODULARIZE is set because abort is used

src/runtime_common.js

@@ -20,8 +20,21 @@
 #include "runtime_asan.js"
 #endif
 
-#if MODULARIZE && USE_READY_PROMISE
-var readyPromiseResolve, readyPromiseReject;
+#if USE_READY_PROMISE
+var readyPromise, readyPromiseResolve, readyPromiseReject;
+function createReadyPromise() {
+#if ASSERTIONS
+  assert(!readyPromise, 'Ready promise already initialized.');
+#endif
+  return new Promise((resolve, reject) => {
+    readyPromiseResolve = resolve;
+    readyPromiseReject = reject;
+  });
+}
+#if !MODULARIZE
+// Modularize mode handles initializing the ready promise.
+readyPromise = createReadyPromise();
+#endif
 #endif
 
 #if PTHREADS || WASM_WORKERS

src/settings_internal.js

@@ -191,9 +191,10 @@ var WASM_EXCEPTIONS = false;
 // EXPORTED_FUNCTIONS then this gets set to 0.
 var EXPECT_MAIN = true;
 
-// Return a "ready" Promise from the MODULARIZE factory function.
-// We disable this under some circumstance if we know its not needed.
-var USE_READY_PROMISE = true;
+// Create a "ready" Promise that is resolved when the Wasm instance is ready.
+// In MODULARIZE mode this Promise is returned from the factory function.
+// We omit the Promise under some circumstance if we know it's not needed.
+var USE_READY_PROMISE = false;
 
 // If true, building against Emscripten's wasm heap memory profiler.
 var MEMORYPROFILER = false;

src/shell_minimal.js

@@ -116,9 +116,9 @@ var err = (...args) => console.error(...args);
 // compilation is ready. In that callback, call the function run() to start
 // the program.
 function ready() {
-#if MODULARIZE && USE_READY_PROMISE
+#if USE_READY_PROMISE
   readyPromiseResolve?.(Module);
-#endif // MODULARIZE
+#endif
 #if INVOKE_RUN && HAS_MAIN
   {{{ runIfMainThread("run();") }}}
 #elif ASSERTIONS

tools/link.py

@@ -1221,15 +1221,20 @@ def limit_incoming_module_api():
   if settings.STACK_OVERFLOW_CHECK >= 2:
     settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$setStackLimits']
 
-  if settings.MODULARIZE:
-    if settings.PROXY_TO_WORKER:
+  if settings.MODULARIZE and settings.PROXY_TO_WORKER:
       exit_with_error('-sMODULARIZE is not compatible with --proxy-to-worker (if you want to run in a worker with -sMODULARIZE, you likely want to do the worker side setup manually)')
-    # in MINIMAL_RUNTIME we may not need to emit the Promise code, as the
-    # HTML output creates a singleton instance, and it does so without the
-    # Promise. However, in Pthreads mode the Promise is used for worker
-    # creation.
-    if settings.MINIMAL_RUNTIME and options.oformat == OFormat.HTML and not settings.PTHREADS:
-      settings.USE_READY_PROMISE = 0
+
+  if settings.AUDIO_WORKLET:
+    # The audio worklet needs to wait for the Wasm module to be instantiated
+    # before it begins processing.
+    settings.USE_READY_PROMISE = 1
+  elif settings.MODULARIZE and (not settings.MINIMAL_RUNTIME or options.oformat != OFormat.HTML or settings.PTHREADS):
+    # Modularize usually requires the ready promise code, but in certain cases
+    # can be omitted. In MINIMAL_RUNTIME we may not need to emit the Promise
+    # code, as the HTML output creates a singleton instance, and it does so
+    # without the Promise. However, in Pthreads mode the Promise is used for
+    # worker creation.
+    settings.USE_READY_PROMISE = 1
 
   check_browser_versions()