Bug 1388728 - Remove eager module instantiation r=bkelly

dom/base/nsJSUtils.cpp

@@ -408,6 +408,7 @@ nsJSUtils::ModuleInstantiate(JSContext* aCx, JS::Handle<JSObject*> aModule)
 
   MOZ_ASSERT(aCx == nsContentUtils::GetCurrentJSContext());
   MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(nsContentUtils::IsInMicroTask());
 
   NS_ENSURE_TRUE(xpc::Scriptability::Get(aModule).Allowed(), NS_OK);
 

dom/script/ModuleLoadRequest.cpp

@@ -95,11 +95,6 @@ ModuleLoadRequest::DependenciesLoaded()
 
   LOG(("ScriptLoadRequest (%p): Module dependencies loaded", this));
 
-  if (!mLoader->InstantiateModuleTree(this)) {
-    LoadFailed();
-    return;
-  }
-
   SetReady();
   mLoader->ProcessLoadedModuleTree(this);
   mLoader = nullptr;

dom/script/ModuleScript.cpp

@@ -30,7 +30,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(ModuleScript)
   NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mModuleRecord)
-  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mException)
 NS_IMPL_CYCLE_COLLECTION_TRACE_END
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(ModuleScript)
@@ -40,13 +39,11 @@ ModuleScript::ModuleScript(ScriptLoader* aLoader, nsIURI* aBaseURL,
                            JS::Handle<JSObject*> aModuleRecord)
  : mLoader(aLoader),
    mBaseURL(aBaseURL),
-   mModuleRecord(aModuleRecord),
-   mInstantiationState(Uninstantiated)
+   mModuleRecord(aModuleRecord)
 {
   MOZ_ASSERT(mLoader);
   MOZ_ASSERT(mBaseURL);
   MOZ_ASSERT(mModuleRecord);
-  MOZ_ASSERT(mException.isUndefined());
 
   // Make module's host defined field point to this module script object.
   // This is cleared in the UnlinkModuleRecord().
@@ -58,13 +55,10 @@ void
 ModuleScript::UnlinkModuleRecord()
 {
   // Remove module's back reference to this object request if present.
-  if (mModuleRecord) {
   MOZ_ASSERT(JS::GetModuleHostDefinedField(mModuleRecord).toPrivate() ==
              this);
   JS::SetModuleHostDefinedField(mModuleRecord, JS::UndefinedValue());
-  }
   mModuleRecord = nullptr;
-  mException.setUndefined();
 }
 
 ModuleScript::~ModuleScript()
@@ -76,21 +70,5 @@ ModuleScript::~ModuleScript()
   DropJSObjects(this);
 }
 
-void
-ModuleScript::SetInstantiationResult(JS::Handle<JS::Value> aMaybeException)
-{
-  MOZ_ASSERT(mInstantiationState == Uninstantiated);
-  MOZ_ASSERT(mModuleRecord);
-  MOZ_ASSERT(mException.isUndefined());
-
-  if (aMaybeException.isUndefined()) {
-    mInstantiationState = Instantiated;
-  } else {
-    mModuleRecord = nullptr;
-    mException = aMaybeException;
-    mInstantiationState = Errored;
-  }
-}
-
 } // dom namespace
 } // mozilla namespace

dom/script/ModuleScript.h

@@ -20,17 +20,9 @@ class ScriptLoader;
 
 class ModuleScript final : public nsISupports
 {
-  enum InstantiationState {
-    Uninstantiated,
-    Instantiated,
-    Errored
-  };
-
   RefPtr<ScriptLoader> mLoader;
   nsCOMPtr<nsIURI> mBaseURL;
   JS::Heap<JSObject*> mModuleRecord;
-  JS::Heap<JS::Value> mException;
-  InstantiationState mInstantiationState;
 
   ~ModuleScript();
 
@@ -44,26 +36,8 @@ public:
 
   ScriptLoader* Loader() const { return mLoader; }
   JSObject* ModuleRecord() const { return mModuleRecord; }
-  JS::Value Exception() const { return mException; }
   nsIURI* BaseURL() const { return mBaseURL; }
 
-  void SetInstantiationResult(JS::Handle<JS::Value> aMaybeException);
-
-  bool IsUninstantiated() const
-  {
-    return mInstantiationState == Uninstantiated;
-  }
-
-  bool IsInstantiated() const
-  {
-    return mInstantiationState == Instantiated;
-  }
-
-  bool InstantiationFailed() const
-  {
-    return mInstantiationState == Errored;
-  }
-
   void UnlinkModuleRecord();
 };
 

dom/script/ScriptLoader.cpp

@@ -400,7 +400,7 @@ ScriptLoader::WaitForModuleFetch(ModuleLoadRequest* aRequest)
 
   RefPtr<ModuleScript> ms;
   MOZ_ALWAYS_TRUE(mFetchedModules.Get(aRequest->mURI, getter_AddRefs(ms)));
-  if (!ms || ms->InstantiationFailed()) {
+  if (!ms) {
     return GenericPromise::CreateAndReject(NS_ERROR_FAILURE, __func__);
   }
 
@@ -664,11 +664,6 @@ ScriptLoader::StartFetchingModuleDependencies(ModuleLoadRequest* aRequest)
   MOZ_ASSERT(aRequest->mModuleScript);
   MOZ_ASSERT(!aRequest->IsReadyToRun());
 
-  if (aRequest->mModuleScript->InstantiationFailed()) {
-    aRequest->LoadFailed();
-    return;
-  }
-
   aRequest->mProgress = ModuleLoadRequest::Progress::FetchingImports;
 
   nsCOMArray<nsIURI> urls;
@@ -763,12 +758,6 @@ HostResolveImportedModule(JSContext* aCx, unsigned argc, JS::Value* vp)
     return HandleModuleNotFound(aCx, script, string);
   }
 
-  if (ms->InstantiationFailed()) {
-    JS::Rooted<JS::Value> exception(aCx, ms->Exception());
-    JS_SetPendingException(aCx, exception);
-    return false;
-  }
-
   *vp = JS::ObjectValue(*ms->ModuleRecord());
   return true;
 }
@@ -804,71 +793,6 @@ ScriptLoader::ProcessLoadedModuleTree(ModuleLoadRequest* aRequest)
   }
 }
 
-bool
-ScriptLoader::InstantiateModuleTree(ModuleLoadRequest* aRequest)
-{
-  // Perform eager instantiation of the loaded module tree.
-
-  MOZ_ASSERT(aRequest);
-
-  LOG(("ScriptLoadRequest (%p): Instantiate module tree", aRequest));
-
-  ModuleScript* ms = aRequest->mModuleScript;
-  MOZ_ASSERT(ms);
-  if (!ms->ModuleRecord()) {
-    return false;
-  }
-
-  AutoJSAPI jsapi;
-  if (NS_WARN_IF(!jsapi.Init(ms->ModuleRecord()))) {
-    return false;
-  }
-
-  nsresult rv = EnsureModuleResolveHook(jsapi.cx());
-  NS_ENSURE_SUCCESS(rv, false);
-
-  JS::Rooted<JSObject*> module(jsapi.cx(), ms->ModuleRecord());
-  bool ok = NS_SUCCEEDED(nsJSUtils::ModuleInstantiate(jsapi.cx(), module));
-
-  JS::RootedValue exception(jsapi.cx());
-  if (!ok) {
-    LOG(("ScriptLoadRequest (%p): Instantiate failed", aRequest));
-    MOZ_ASSERT(jsapi.HasException());
-    if (!jsapi.StealException(&exception)) {
-      return false;
-    }
-    MOZ_ASSERT(!exception.isUndefined());
-  }
-
-  // Mark this module and any uninstantiated dependencies found via depth-first
-  // search as instantiated and record any error.
-
-  mozilla::Vector<ModuleLoadRequest*, 1> requests;
-  if (!requests.append(aRequest)) {
-    return false;
-  }
-
-  while (!requests.empty()) {
-    ModuleLoadRequest* request = requests.popCopy();
-    ModuleScript* ms = request->mModuleScript;
-    if (!ms->IsUninstantiated()) {
-      continue;
-    }
-
-    ms->SetInstantiationResult(exception);
-
-    for (auto import : request->mImports) {
-      if (import->mModuleScript->IsUninstantiated() &&
-          !requests.append(import))
-      {
-        return false;
-      }
-    }
-  }
-
-  return true;
-}
-
 nsresult
 ScriptLoader::RestartLoad(ScriptLoadRequest* aRequest)
 {
@@ -2069,6 +1993,9 @@ ScriptLoader::EvaluateScript(ScriptLoadRequest* aRequest)
     AutoCurrentScriptUpdater scriptUpdater(this, aRequest->mElement);
 
     if (aRequest->IsModuleRequest()) {
+      rv = EnsureModuleResolveHook(aes.cx());
+      NS_ENSURE_SUCCESS(rv, rv);
+
       // When a module is already loaded, it is not feched a second time and the
       // mDataType of the request might remain set to DataType::Unknown.
       MOZ_ASSERT(!aRequest->IsBytecode());
@@ -2076,15 +2003,11 @@ ScriptLoader::EvaluateScript(ScriptLoadRequest* aRequest)
       ModuleLoadRequest* request = aRequest->AsModuleRequest();
       MOZ_ASSERT(request->mModuleScript);
       MOZ_ASSERT(!request->mOffThreadToken);
-      ModuleScript* ms = request->mModuleScript;
-      MOZ_ASSERT(!ms->IsUninstantiated());
-      if (ms->InstantiationFailed()) {
-        JS::Rooted<JS::Value> exception(aes.cx(), ms->Exception());
-        JS_SetPendingException(aes.cx(), exception);
-        rv = NS_ERROR_FAILURE;
-      } else {
-        JS::Rooted<JSObject*> module(aes.cx(), ms->ModuleRecord());
+      JS::Rooted<JSObject*> module(aes.cx(),
+                                   request->mModuleScript->ModuleRecord());
       MOZ_ASSERT(module);
+      rv = nsJSUtils::ModuleInstantiate(aes.cx(), module);
+      if (NS_SUCCEEDED(rv)) {
         rv = nsJSUtils::ModuleEvaluate(aes.cx(), module);
       }
       aRequest->mCacheInfo = nullptr;

dom/script/ScriptLoader.h

@@ -476,7 +476,6 @@ private:
   nsresult CreateModuleScript(ModuleLoadRequest* aRequest);
   nsresult ProcessFetchedModuleSource(ModuleLoadRequest* aRequest);
   void ProcessLoadedModuleTree(ModuleLoadRequest* aRequest);
-  bool InstantiateModuleTree(ModuleLoadRequest* aRequest);
   void StartFetchingModuleDependencies(ModuleLoadRequest* aRequest);
 
   RefPtr<mozilla::GenericPromise>