Bug 1540913 - Part 3: Exit early if worker module evaluation is aborted; r=jonco

This change addresses the second issue around worker shutdown with infinitely running dynamic
imports: As the event loop is prevented from running when the worker is dying, we do not want to
delegate to the event loop in this case. This case always has a failing promise. Since this is a
failure case related to the worker dying, we stop running code, rather
than waiting for a tick (that never comes) from the event loop.

Differential Revision: https://phabricator.services.mozilla.com/D171684

dom/workers/loader/WorkerModuleLoader.cpp

@@ -9,6 +9,7 @@
 #include "mozilla/dom/WorkerLoadContext.h"
 #include "mozilla/dom/WorkerPrivate.h"
 #include "mozilla/dom/workerinternals/ScriptLoader.h"
+#include "mozilla/dom/WorkerScope.h"
 #include "WorkerModuleLoader.h"
 
 #include "nsISupportsImpl.h"
@@ -123,4 +124,10 @@ void WorkerModuleLoader::OnModuleLoadComplete(ModuleLoadRequest* aRequest) {
   }
 }
 
+bool WorkerModuleLoader::IsModuleEvaluationAborted(
+    ModuleLoadRequest* aRequest) {
+  WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+  return workerPrivate->GlobalScope()->IsDying();
+}
+
 }  // namespace mozilla::dom::workerinternals::loader

dom/workers/loader/WorkerModuleLoader.h

@@ -67,6 +67,8 @@ class WorkerModuleLoader : public JS::loader::ModuleLoaderBase {
       JS::MutableHandle<JSObject*> aModuleScript) override;
 
   void OnModuleLoadComplete(ModuleLoadRequest* aRequest) override;
+
+  bool IsModuleEvaluationAborted(ModuleLoadRequest* aRequest) override;
 };
 
 }  // namespace mozilla::dom::workerinternals::loader

js/loader/ModuleLoaderBase.cpp

@@ -1227,16 +1227,11 @@ nsresult ModuleLoaderBase::EvaluateModuleInContext(
   // unless the user cancels execution.
   MOZ_ASSERT_IF(ok, !JS_IsExceptionPending(aCx));
 
-  // For long running scripts, the request may be cancelled abruptly. This
-  // may also happen if the loader is collected before we get here.
-  if (request->IsCanceled() || !mLoader) {
-    return NS_ERROR_ABORT;
-  }
-
-  if (!ok) {
+  if (!ok || IsModuleEvaluationAborted(request)) {
     LOG(("ScriptLoadRequest (%p):   evaluation failed", aRequest));
     // For a dynamic import, the promise is rejected. Otherwise an error is
     // reported by AutoEntryScript.
+    rv = NS_ERROR_ABORT;
   }
 
   // ModuleEvaluate returns a promise unless the user cancels the execution in
@@ -1248,7 +1243,11 @@ nsresult ModuleLoaderBase::EvaluateModuleInContext(
   }
 
   if (request->IsDynamicImport()) {
+    if (NS_FAILED(rv)) {
+      FinishDynamicImportAndReject(request, rv);
+    } else {
       FinishDynamicImport(aCx, request, NS_OK, evaluationPromise);
+    }
   } else {
     // If this is not a dynamic import, and if the promise is rejected,
     // the value is unwrapped from the promise value.

js/loader/ModuleLoaderBase.h

@@ -246,6 +246,10 @@ class ModuleLoaderBase : public nsISupports {
   // Called when a module script has been loaded, including imports.
   virtual void OnModuleLoadComplete(ModuleLoadRequest* aRequest) = 0;
 
+  virtual bool IsModuleEvaluationAborted(ModuleLoadRequest* aRequest) {
+    return false;
+  }
+
   // Get the error message when resolving failed. The default is to call
   // nsContentUtils::FormatLoalizedString. But currently
   // nsContentUtils::FormatLoalizedString cannot be called on a worklet thread,