[ES6 modules] ScriptModule::compile() exceptions are handled via isolate's MessageListener

third_party/WebKit/Source/bindings/core/v8/ScriptModule.cpp

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "bindings/core/v8/ScriptModule.h"
 
 #include "bindings/core/v8/V8Binding.h"
 #include "core/dom/Modulator.h"
 #include "core/dom/ScriptModuleResolver.h"
 
 namespace blink {
 
 ScriptModule::ScriptModule(v8::Isolate* isolate, v8::Local<v8::Module> module)
     : m_module(SharedPersistent<v8::Module>::create(module, isolate)) {}
 
 ScriptModule::~ScriptModule() {}
 
 ScriptModule ScriptModule::compile(v8::Isolate* isolate,
                                    const String& source,
                                    const String& fileName) {
   v8::TryCatch tryCatch(isolate);
   tryCatch.SetVerbose(true);
   v8::Local<v8::Module> module;
   if (!v8Call(V8ScriptRunner::compileModule(isolate, source, fileName), module,
               tryCatch)) {
-    // TODO(adamk): Signal failure somehow.
-    return ScriptModule(isolate, module);
+    // Compilation error is not used in Blink implementaion logic.
+    // Note: Error message is delivered to user (e.g. console) by message
+    // listeners set on v8::Isolate. See V8Initializer::initalizeMainThread().
+    // TODO(nhiroki): Revisit this when supporting modules on worker threads.
+    DCHECK(tryCatch.HasCaught());
+    return ScriptModule();
   }
+  DCHECK(!tryCatch.HasCaught());
   return ScriptModule(isolate, module);
 }
 
 ScriptValue ScriptModule::instantiate(ScriptState* scriptState) {
   v8::Isolate* isolate = scriptState->isolate();
   v8::TryCatch tryCatch(isolate);
 
   DCHECK(!isNull());
   v8::Local<v8::Context> context = scriptState->context();
   bool success = m_module->newLocal(scriptState->isolate())
@@ skipping 34 matching lines @@
   if (resolved.isNull()) {
     DCHECK(exceptionState.hadException());
     return v8::MaybeLocal<v8::Module>();
   }
 
   DCHECK(!exceptionState.hadException());
   return v8::MaybeLocal<v8::Module>(resolved.m_module->newLocal(isolate));
 }
 
 }  // namespace blink