[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/fetch/ResourceOwner.h"
+#include "core/loader/resource/ScriptResource.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 ModuleLoader;
+class ResourceFetcher;
+class ScriptController;
+class ModuleLoaderRegistry;
+
+// A ModuleLoader is responsible for loading a single ScriptModule.
+//
+// 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

[dominicc (has gone to gerrit), 2016/12/19 10:07:51]

still some disfluency here

+// 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);
+
+  enum class State {
+    Initial,
+    // FetchRequest is being processed, and ModuleLoader hasn't
+    // notifyFinished().
+    Fetching,
+    // Finished successfully or w/ error.
+    Finished,
+  };
+
+ public:
+  class Client : public GarbageCollectedMixin {
+   private:
+    friend class ModuleLoader;
+    virtual void notifyFinished(ScriptModule) = 0;
+  };
+  // Call via ModuleLoaderRegistry::fetch.
+  static ModuleLoader* fetch(const KURL&,
+                             ScriptController*,
+                             ResourceFetcher*,
+                             ModuleLoaderRegistry*,
+                             Client*);
+
+  ~ModuleLoader() = default;
+
+  bool isFetching() const { return m_state == State::Fetching; }

[dominicc (has gone to gerrit), 2016/12/19 10:07:51]

Why not just have a state() accessor?

[kouhei (in TOK), 2016/12/19 11:19:59]

I'm not sure if we want to expose all internal states. I plan to introduce at
least one more states to async evaluate fetched module script, which wouldn't
need to be known outside ModuleLoader.

+  bool hasFinished() const { return m_state == State::Finished; }
+
+  DECLARE_TRACE();
+
+ private:
+  explicit ModuleLoader(const KURL&,
+                        ScriptController*,
+                        ModuleLoaderRegistry*,
+                        Client*);
+
+  void fetchInternal(ResourceFetcher*);
+
+  void advanceState(State newState);
+
+  // Implements ScriptResourceClient
+  void notifyFinished(Resource*) override;
+  String debugName() const override { return "ModuleLoader"; }
+
+  // TODO(kouhei): May be this method should live in ModuleResource? or should
+  // it be here to consolidate the spec impl code in ModuleMap.cpp?
+  static bool wasModuleLoadSuccessful(Resource*);
+
+  KURL m_url;
+  Member<ScriptController> m_scriptController;
+  State m_state = State::Initial;
+  bool m_wasLoadSuccessful = true;

[dominicc (has gone to gerrit), 2016/12/19 10:07:51]

Maybe it's more robust to represent this in m_state, like with Finished_Success
and Finished_Failure. Seems less likely you'd consult m_wasLoadSuccessful before
finish by accident.

[kouhei (in TOK), 2016/12/19 11:19:59]

This flag is no longer used. Let me remove this flag.

[kouhei (in TOK), 2016/12/20 10:47:35]

Done.

+  ScriptModule m_scriptModule;
+  Member<ModuleLoaderRegistry> m_registry;
+  Member<Client> m_client;
+};
+
+// ModuleLoaderRegistry keeps active ModuleLoaders alive.
+class ModuleLoaderRegistry : public GarbageCollected<ModuleLoaderRegistry> {
+ public:
+  static ModuleLoaderRegistry* create() { return new ModuleLoaderRegistry; }
+  DECLARE_TRACE();
+
+  ModuleLoader* fetch(const KURL&,
+                      ScriptController*,
+                      ResourceFetcher*,
+                      ModuleLoader::Client*);
+
+ private:
+  ModuleLoaderRegistry() = default;
+
+  friend class ModuleLoader;
+  void releaseFinishedLoader(ModuleLoader*);
+
+  HeapHashSet<Member<ModuleLoader>> m_activeLoaders;
+};
+
+class ModuleMap : public GarbageCollected<ModuleMap> {
+  WTF_MAKE_NONCOPYABLE(ModuleMap);
+  class Entry;
+  class LoaderHost;
+
+ public:
+  class Client : public GarbageCollectedMixin {
+   private:
+    friend class ModuleMap::Entry;

[dominicc (has gone to gerrit), 2016/12/19 10:07:51]

Inline module scripts aren't entered into the map! Do they get entries with
funky keys, so nobody else can look them up? Or is there something which adapts
the ModuleLoader's client interface to Entry's client interface? If so, does
this need to be a friend of that too?

[kouhei (in TOK), 2016/12/19 11:20:00]

Ack. Let this be Modulator::Client after ModuleMap split.

+    virtual void notifyFinished(ScriptModule) = 0;
+  };
+
+  static ModuleMap* create(ScriptController* controller,
+                           ResourceFetcher* fetcher) {
+    return new ModuleMap(controller, fetcher);
+  }
+  DECLARE_TRACE();
+
+  // https://html.spec.whatwg.org/#fetch-a-single-module-script
+  void fetchSingle(
+      const KURL&,
+      Client*

[dominicc (has gone to gerrit), 2016/12/19 10:07:51]

Yay. I guess we shouldn't just use a callback because we want to trace that
thing for GC?

[kouhei (in TOK), 2016/12/19 11:20:00]

Callback supports Oilpan, but via Persistent, which means that we need to care
cycles.
Given that clients are likely complex enough to be implemented as classes, I
think this is fine.

+      /*, 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*/);
+
+ private:
+  ModuleMap(ScriptController*, ResourceFetcher*);
+  ModuleMap() = delete;
+
+  using MapImpl = HeapHashMap<KURL, Member<Entry>>;
+
+  // A module map is a map of absolute URLs to map entry.
+  MapImpl m_map;
+
+  // Below should be moved to the modulator.
+  Member<ScriptController> m_scriptController;
+  Member<ResourceFetcher> m_fetcher;
+  Member<ModuleLoaderRegistry> m_loaderRegistry;
+};
+
+}  // namespace blink
+
+#endif