[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 "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 ModuleScript : public GarbageCollected<ModuleScript> {

[adamk, 2016/12/06 21:19:00]

Is this the same thing as the previously-discussed "ScriptModule" (which would
be a wrapper around a v8::Module)? Or does this hold a ScriptModule?

[kouhei (in TOK), 2016/12/08 03:20:38]

Yes. Let's rename this to ScriptModule.

+ public:
+  static ModuleScript* create() { return new ModuleScript(); }
+  DEFINE_INLINE_TRACE() {}
+
+ private:
+  ModuleScript() {}
+};
+
+class ModuleMap : public GarbageCollected<ModuleMap> {
+  WTF_MAKE_NONCOPYABLE(ModuleMap);
+
+ public:
+  static ModuleMap* create(ResourceFetcher* fetcher) { return new ModuleMap(fetcher); }
+  DECLARE_TRACE();
+
+  // https://html.spec.whatwg.org/#fetch-a-single-module-script
+  void fetch(
+      const KURL& url
+      /*, 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*/);  // => ModuleScript*
+
+ private:
+  ModuleMap(ResourceFetcher*);
+  ModuleMap() = delete;
+
+  // 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 Entry {
+   public:
+    DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
+
+    enum class State {
+      Fetching,
+      Fetched,
+      Failed,
+      Deleted,
+    };
+
+    Entry() : m_state(State::Fetching) {}
+    Entry(WTF::HashTableDeletedValueType) : m_state(State::Deleted) {}
+
+    bool isFetching() const { return m_state == State::Fetching; }
+
+    ModuleScript* moduleScript() {
+      if (!m_moduleScript)
+        return nullptr;
+
+      DCHECK_EQ(m_state, State::Fetched);
+      return m_moduleScript;
+    }
+
+    DEFINE_INLINE_TRACE() { visitor->trace(m_moduleScript); }
+
+   private:
+    State m_state;
+    Member<ModuleScript> m_moduleScript;
+  };
+
+  using MapImpl = HeapHashMap<KURL, Entry>;
+
+  // A module map is a map of absolute URLs to values
+  MapImpl m_map;
+
+  Member<ResourceFetcher> m_fetcher;
+};
+
+}  // namespace blink
+
+#endif