Issue #618 - Align error handling for module scripts with the spec (again)

This updates module implementation to match spec regarding handling of
instantiation errors, after it was changed yet again, this time to not remember
instantiation errors, but instead immediately rethrow applicable ones.

Ref: BZ 1420420

dom/script/ScriptLoader.cpp

@@ -493,7 +493,7 @@ ScriptLoader::ProcessFetchedModuleSource(ModuleLoadRequest* aRequest)
     return rv;
   }
 
-  if (!aRequest->mModuleScript->IsErrored()) {
+  if (!aRequest->mModuleScript->HasParseError()) {
     StartFetchingModuleDependencies(aRequest);
   }
 
@@ -568,7 +568,7 @@ ScriptLoader::CreateModuleScript(ModuleLoadRequest* aRequest)
         return NS_ERROR_FAILURE;
       }
 
-      moduleScript->SetPreInstantiationError(error);
+      moduleScript->SetParseError(error);
       aRequest->ModuleErrored();
       return NS_OK;
     }
@@ -580,8 +580,6 @@ ScriptLoader::CreateModuleScript(ModuleLoadRequest* aRequest)
     nsCOMArray<nsIURI> urls;
     rv = ResolveRequestedModules(aRequest, urls);
     if (NS_FAILED(rv)) {
-      // ResolveRequestedModules sets pre-instanitation error on failure.
-      MOZ_ASSERT(moduleScript->IsErrored());
       aRequest->ModuleErrored();
       return NS_OK;
     }
@@ -627,7 +625,7 @@ HandleResolveFailure(JSContext* aCx, ModuleScript* aScript,
     return NS_ERROR_OUT_OF_MEMORY;
   }
 
-  aScript->SetPreInstantiationError(error);
+  aScript->SetParseError(error);
   return NS_OK;
 }
 
@@ -723,7 +721,6 @@ ResolveRequestedModules(ModuleLoadRequest* aRequest, nsCOMArray<nsIURI> &aUrls)
     }
 
     // Let url be the result of resolving a module specifier given module script and requested.
-    ModuleScript* ms = aRequest->mModuleScript;
     nsCOMPtr<nsIURI> uri = ResolveModuleSpecifier(ms, specifier);
     if (!uri) {
       nsresult rv = HandleResolveFailure(cx, ms, specifier);
@@ -746,7 +743,7 @@ void
 ScriptLoader::StartFetchingModuleDependencies(ModuleLoadRequest* aRequest)
 {
   MOZ_ASSERT(aRequest->mModuleScript);
-  MOZ_ASSERT(!aRequest->mModuleScript->IsErrored());
+  MOZ_ASSERT(!aRequest->mModuleScript->HasParseError());
   MOZ_ASSERT(!aRequest->IsReadyToRun());
 
   aRequest->mProgress = ModuleLoadRequest::Progress::FetchingImports;
@@ -843,7 +840,7 @@ HostResolveImportedModule(JSContext* aCx, unsigned argc, JS::Value* vp)
   ModuleScript* ms = script->Loader()->GetFetchedModule(uri);
   MOZ_ASSERT(ms, "Resolved module not found in module map");
 
-  MOZ_ASSERT(!ms->IsErrored());
+  MOZ_ASSERT(!ms->HasParseError());
 
   *vp = JS::ObjectValue(*ms->ModuleRecord());
   return true;
@@ -871,18 +868,16 @@ void
 ScriptLoader::CheckModuleDependenciesLoaded(ModuleLoadRequest* aRequest)
 {
   RefPtr<ModuleScript> moduleScript = aRequest->mModuleScript;
-  if (moduleScript && !moduleScript->IsErrored()) {
-    for (auto childRequest : aRequest->mImports) {
-      ModuleScript* childScript = childRequest->mModuleScript;
-      if (!childScript) {
-        // Load error
-        aRequest->mModuleScript = nullptr;
-        return;
-      } else if (childScript->IsErrored()) {
-        // Script error
-        moduleScript->SetPreInstantiationError(childScript->Error());
-        return;
-      }
+  if (!moduleScript || moduleScript->HasParseError()) {
+    return;
+  }
+
+  for (auto childRequest : aRequest->mImports) {
+    ModuleScript* childScript = childRequest->mModuleScript;
+    if (!childScript) {
+      aRequest->mModuleScript = nullptr;
+      // Load error on script load request; bail.
+      return;
     }
   }
 }
@@ -892,7 +887,7 @@ ScriptLoader::ProcessLoadedModuleTree(ModuleLoadRequest* aRequest)
 {
   if (aRequest->IsTopLevel()) {
     ModuleScript* moduleScript = aRequest->mModuleScript;
-    if (moduleScript && !moduleScript->IsErrored()) {
+    if (moduleScript && !moduleScript->HasErrorToRethrow()) {
       if (!InstantiateModuleTree(aRequest)) {
         aRequest->mModuleScript = nullptr;
       }
@@ -906,6 +901,28 @@ ScriptLoader::ProcessLoadedModuleTree(ModuleLoadRequest* aRequest)
   }
 }
 
+JS::Value
+ScriptLoader::FindFirstParseError(ModuleLoadRequest* aRequest)
+{
+  MOZ_ASSERT(aRequest);
+
+  ModuleScript* moduleScript = aRequest->mModuleScript;
+  MOZ_ASSERT(moduleScript);
+
+  if (moduleScript->HasParseError()) {
+    return moduleScript->ParseError();
+  }
+
+  for (ModuleLoadRequest* childRequest : aRequest->mImports) {
+    JS::Value error = FindFirstParseError(childRequest);
+    if (!error.isUndefined()) {
+      return error;
+    }
+  }
+
+  return JS::UndefinedValue();
+}
+
 bool
 ScriptLoader::InstantiateModuleTree(ModuleLoadRequest* aRequest)
 {
@@ -916,6 +933,14 @@ ScriptLoader::InstantiateModuleTree(ModuleLoadRequest* aRequest)
 
   ModuleScript* moduleScript = aRequest->mModuleScript;
   MOZ_ASSERT(moduleScript);
+
+  JS::Value parseError = FindFirstParseError(aRequest);
+  if (!parseError.isUndefined()) {
+    // Parse error found in the requested script
+    moduleScript->SetErrorToRethrow(parseError);
+    return true;
+  }
+
   MOZ_ASSERT(moduleScript->ModuleRecord());
 
   nsAutoMicroTask mt;
@@ -937,7 +962,7 @@ ScriptLoader::InstantiateModuleTree(ModuleLoadRequest* aRequest)
       return false;
     }
     MOZ_ASSERT(!exception.isUndefined());
-    // Ignore the exception. It will be recorded in the module record.
+    moduleScript->SetErrorToRethrow(exception);
   }
 
   return true;
@@ -1462,7 +1487,7 @@ ScriptLoader::ProcessScriptElement(nsIScriptElement *aElement)
     } else {
       AddDeferRequest(request);
     }
-    if (!modReq->mModuleScript->IsErrored()) {
+    if (!modReq->mModuleScript->HasParseError()) {
       StartFetchingModuleDependencies(modReq);
     }
     return false;
@@ -1966,9 +1991,9 @@ ScriptLoader::EvaluateScript(ScriptLoadRequest* aRequest)
       MOZ_ASSERT(!request->mOffThreadToken);
 
       ModuleScript* moduleScript = request->mModuleScript;
-      if (moduleScript->IsErrored()) {
-        // Module has an error status
-        JS::Rooted<JS::Value> error(cx, moduleScript->Error());
+      if (moduleScript->HasErrorToRethrow()) {
+        // Module has an error status to be rethrown
+        JS::Rooted<JS::Value> error(cx, moduleScript->ErrorToRethrow());
         JS_SetPendingException(cx, error);
         return NS_OK; // An error is reported by AutoEntryScript.
       }