[WIP Prototype] ES6 https://html.spec.whatwg.org/#fetch-a-single-module-script implementation

third_party/WebKit/Source/core/dom/ModuleMap.h

+// Copyright 2016 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.
+
+#ifndef ModuleMap_h
+#define ModuleMap_h
+
+#include "bindings/core/v8/ScriptModule.h"
+#include "core/loader/resource/ScriptResource.h"
+#include "core/fetch/ResourceOwner.h"
+#include "platform/heap/Handle.h"
+#include "platform/weborigin/KURL.h"
+#include "platform/weborigin/KURLHash.h"
+#include "wtf/HashMap.h"
+#include "wtf/HashTableDeletedValueType.h"
+
+namespace blink {
+
+class ResourceFetcher;
+class ModuleLoader;
+
+enum class ModuleLoaderState {
+  Initial,
+  Fetching,
+  Fetched,

[kouhei (in TOK), 2016/12/12 07:38:51]

TODO: Fetched, Failed -> Complete or Finished and don't store error info here.

+  Failed,
+};
+
+class ModuleLoaderClient : public GarbageCollectedMixin {
+ public:
+  DEFINE_INLINE_VIRTUAL_TRACE() {}
+
+ protected:
+  ModuleLoaderClient() {};
+  virtual ~ModuleLoaderClient();
+
+ private:
+  friend class ModuleLoader;
+  virtual void notifyFinished() = nullptr;
+
+  // Called by ModuleLoader to catch up the client to the latest ModuleLoader state.
+  virtual void catchUpToLatestStateIfNeeded(ModuleLoaderState);
+
+  ModuleLoaderState m_state = ModuleLoaderState::Initial;
+};
+
+// A ModuleLoader is responsible for loading a single module.
+//
+// A ModuleLoader constructs and emit FetchRequest to RequestFetcher (via
+// ScriptResource::fetch).
+// Then, it keeps track of the fetch progress by being a ScriptResourceClient.
+//
+// either a module script, null (used to represent failed fetches), or a
+// placeholder value "fetching". Module maps are used to ensure that imported
+// JavaScript modules are only fetched, parsed, and evaluated once per
+// Document or worker.
+class ModuleLoader final : public GarbageCollectedFinalized<ModuleLoader>,
+                           public ResourceOwner<ScriptResource> {
+  WTF_MAKE_NONCOPYABLE(ModuleLoader);
+  USING_GARBAGE_COLLECTED_MIXIN(ModuleLoader);
+
+ public:
+  static ModuleLoader* create(const KURL& url) { return new ModuleLoader(url); }
+
+  ~ModuleLoader();
+
+  void fetch(ResourceFetcher* fetcher);
+  bool isFetching() const { return m_state == State::Fetching; }
+  bool isFinished() const { return m_state == State::Fetched || m_state == State::Failed; }
+
+  // Run callbacks for the given client till current state, and register the
+  // client to receive further callbacks if !isFinished() loading.
+  void addClient(ModuleLoaderClient*);
+
+  ScriptModule& moduleScript() {
+    if (m_scriptModule.isNull())
+      return m_scriptModule;
+
+    DCHECK_EQ(m_state, State::Fetched);
+    return m_scriptModule;
+  }
+
+  DECLARE_TRACE();
+
+ private:
+  ModuleLoader(const KURL& url);
+
+  void advanceState(State newState);
+
+  enum class FlushType : bool {
+    NoStateChange,
+    MayHaveAdvancedState 
+  };
+
+  // Ensure all clients (including those added during notification callbacks) receives notifications up to 
+  void notifyAndFlushPendingClients();
+  void addSinglePendingClient();
+
+  // Implements ScriptResourceClient
+  void notifyFinished(Resource*) override;
+  String debugName() const override { return "ModuleLoader"; }
+
+  KURL m_url;
+  State m_state;
+  ScriptModule m_scriptModule;
+
+  bool m_insideAddPendingClientsLoop = false;
+  HeapHashSet<Member<ModuleLoaderClient>> m_clients;
+  HeapHashSet<Member<ModuleLoaderClient>> m_pendingClients;
+};
+
+class ModuleMap : public GarbageCollected<ModuleMap> {
+  WTF_MAKE_NONCOPYABLE(ModuleMap);
+
+ public:
+  static ModuleMap* create(LocalFrame* frame, ResourceFetcher* fetcher) {
+    return new ModuleMap(frame, fetcher);
+  }
+  DECLARE_TRACE();
+
+  // https://html.spec.whatwg.org/#fetch-a-single-module-script
+  void fetch(
+      const KURL& url,
+      ModuleLoaderClient* client
+      /*, a fetch client settings object, a destination, a cryptographic nonce, a parser state, a credentials mode, a module map settings object, a referrer, and a top-level module fetch flag*/);  // => ScriptModule*
+
+ private:
+  ModuleMap(LocalFrame*, ResourceFetcher*);
+  ModuleMap() = delete;
+
+  using MapImpl = HeapHashMap<KURL, Member<ModuleLoader>>;
+
+  // A module map is a map of absolute URLs to values
+  MapImpl m_map;
+
+  Member<LocalFrame> m_frame;
+  Member<ResourceFetcher> m_fetcher;
+};
+
+}  // namespace blink
+
+#endif