Bug 1523897 - Only initialize debugger data for modules the first time they are executed r=smaug

dom/script/LoadedScript.cpp

@@ -123,7 +123,7 @@ NS_IMPL_RELEASE_INHERITED(ModuleScript, LoadedScript)
 
 ModuleScript::ModuleScript(ScriptFetchOptions* aFetchOptions, nsIURI* aBaseURL)
     : LoadedScript(ScriptKind::eModule, aFetchOptions, aBaseURL),
-      mSourceElementAssociated(false) {
+      mDebuggerDataInitialized(false) {
   MOZ_ASSERT(!ModuleRecord());
   MOZ_ASSERT(!HasParseError());
   MOZ_ASSERT(!HasErrorToRethrow());
@@ -182,11 +182,11 @@ void ModuleScript::SetErrorToRethrow(const JS::Value& aError) {
   mErrorToRethrow = aError;
 }
 
-void ModuleScript::SetSourceElementAssociated() {
+void ModuleScript::SetDebuggerDataInitialized() {
   MOZ_ASSERT(ModuleRecord());
-  MOZ_ASSERT(!mSourceElementAssociated);
+  MOZ_ASSERT(!mDebuggerDataInitialized);
 
-  mSourceElementAssociated = true;
+  mDebuggerDataInitialized = true;
 }
 
 }  // namespace dom

dom/script/LoadedScript.h

@@ -64,7 +64,7 @@ class ModuleScript final : public LoadedScript {
   JS::Heap<JSObject*> mModuleRecord;
   JS::Heap<JS::Value> mParseError;
   JS::Heap<JS::Value> mErrorToRethrow;
-  bool mSourceElementAssociated;
+  bool mDebuggerDataInitialized;
 
   ~ModuleScript();
 
@@ -78,7 +78,7 @@ class ModuleScript final : public LoadedScript {
   void SetModuleRecord(JS::Handle<JSObject*> aModuleRecord);
   void SetParseError(const JS::Value& aError);
   void SetErrorToRethrow(const JS::Value& aError);
-  void SetSourceElementAssociated();
+  void SetDebuggerDataInitialized();
 
   JSObject* ModuleRecord() const { return mModuleRecord; }
 
@@ -86,7 +86,7 @@ class ModuleScript final : public LoadedScript {
   JS::Value ErrorToRethrow() const { return mErrorToRethrow; }
   bool HasParseError() const { return !mParseError.isUndefined(); }
   bool HasErrorToRethrow() const { return !mErrorToRethrow.isUndefined(); }
-  bool SourceElementAssociated() const { return mSourceElementAssociated; }
+  bool DebuggerDataInitialized() const { return mDebuggerDataInitialized; }
 
   void UnlinkModuleRecord();
 

dom/script/ScriptLoader.cpp

@@ -1108,21 +1108,22 @@ bool ScriptLoader::InstantiateModuleTree(ModuleLoadRequest* aRequest) {
   return true;
 }
 
-nsresult ScriptLoader::AssociateSourceElementsForModuleTree(
+nsresult ScriptLoader::InitDebuggerDataForModuleTree(
     JSContext* aCx, ModuleLoadRequest* aRequest) {
-  // Preloading can cause JS scripts to be compiled before DOM script element
-  // nodes have been created. This method ensures compiled scripts are
-  // associated with DOM element nodes before execution.
+  // JS scripts can be associated with a DOM element for use by the debugger,
+  // but preloading can cause scripts to be compiled before DOM script element
+  // nodes have been created. This method ensures that this association takes
+  // place before the first time a module script is run.
 
   MOZ_ASSERT(aRequest);
 
   ModuleScript* moduleScript = aRequest->mModuleScript;
-  if (moduleScript->SourceElementAssociated()) {
+  if (moduleScript->DebuggerDataInitialized()) {
     return NS_OK;
   }
 
   for (ModuleLoadRequest* childRequest : aRequest->mImports) {
-    nsresult rv = AssociateSourceElementsForModuleTree(aCx, childRequest);
+    nsresult rv = InitDebuggerDataForModuleTree(aCx, childRequest);
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
@@ -1133,13 +1134,13 @@ nsresult ScriptLoader::AssociateSourceElementsForModuleTree(
   if (element) {
     nsresult rv = nsJSUtils::InitModuleSourceElement(aCx, module, element);
     NS_ENSURE_SUCCESS(rv, rv);
-    moduleScript->SetSourceElementAssociated();
   }
 
   // The script is now ready to be exposed to the debugger.
   JS::Rooted<JSScript*> script(aCx, JS::GetModuleScript(module));
   JS::ExposeScriptToDebugger(aCx, script);
 
+  moduleScript->SetDebuggerDataInitialized();
   return NS_OK;
 }
 
@@ -2576,10 +2577,8 @@ nsresult ScriptLoader::EvaluateScript(ScriptLoadRequest* aRequest) {
       JS::Rooted<JSObject*> module(cx, moduleScript->ModuleRecord());
       MOZ_ASSERT(module);
 
-      if (!moduleScript->SourceElementAssociated()) {
-        rv = AssociateSourceElementsForModuleTree(cx, request);
-        NS_ENSURE_SUCCESS(rv, rv);
-      }
+      rv = InitDebuggerDataForModuleTree(cx, request);
+      NS_ENSURE_SUCCESS(rv, rv);
 
       rv = nsJSUtils::ModuleEvaluate(cx, module);
       MOZ_ASSERT(NS_FAILED(rv) == aes.HasException());

dom/script/ScriptLoader.h

@@ -524,8 +524,8 @@ class ScriptLoader final : public nsISupports {
   RefPtr<mozilla::GenericPromise> StartFetchingModuleAndDependencies(
       ModuleLoadRequest* aParent, nsIURI* aURI);
 
-  nsresult AssociateSourceElementsForModuleTree(JSContext* aCx,
-                                                ModuleLoadRequest* aRequest);
+  nsresult InitDebuggerDataForModuleTree(JSContext* aCx,
+                                         ModuleLoadRequest* aRequest);
 
   void RunScriptWhenSafe(ScriptLoadRequest* aRequest);