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

third_party/WebKit/Source/core/loader/modulescript/ModuleTreeLinker.h

+// 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.
+
+#ifndef ModuleTreeLinker_h
+#define ModuleTreeLinker_h
+
+#include "core/dom/AncestorList.h"
+#include "core/dom/Modulator.h"
+
+namespace blink {
+
+class ModuleScriptFetchRequest;
+enum class ModuleGraphLevel;
+class ModuleTreeLinkerRegistry;
+
+// A ModuleTreeLinker is responsible for running and keeping intermediate states
+// for "internal module script graph fetching procedure" for a module graph tree
+// node.
+// https://html.spec.whatwg.org/multipage/webappapis.html#internal-module-script-graph-fetching-procedure
+class ModuleTreeLinker final
+    : public GarbageCollectedFinalized<ModuleTreeLinker>,
+      public SingleModuleClient {
+  USING_GARBAGE_COLLECTED_MIXIN(ModuleTreeLinker);
+
+ public:
+  static ModuleTreeLinker* fetch(const ModuleScriptFetchRequest&,
+                                 const AncestorList&,
+                                 ModuleGraphLevel,
+                                 Modulator*,
+                                 ModuleTreeLinkerRegistry*,
+                                 ModuleTreeClient*);
+  virtual ~ModuleTreeLinker() = default;
+  DECLARE_TRACE();
+
+  bool isFetching() const {
+    return State::FetchingSelf <= m_state && m_state < State::Finished;
+  }
+  bool hasFinished() const { return m_state == State::Finished; }
+
+ private:
+  ModuleTreeLinker(const AncestorList& ancestorListWithUrl,
+                   Modulator*,
+                   ModuleTreeLinkerRegistry*,
+                   ModuleTreeClient*);
+
+  enum class State {
+    Initial,
+    // Running fetch of the module script corresponding to the target node.
+    FetchingSelf,
+    // Running fetch of descendants of the target node.
+    FetchingDependencies,
+    // Instantiating m_moduleScript and the node descendants.
+    Instantiating,
+    Finished,
+  };
+  void advanceState(State);
+
+  void fetchSelf(const ModuleScriptFetchRequest&, ModuleGraphLevel);
+  // Implements SingleModuleClient
+  void notifyModuleLoadFinished(ModuleScript*) override;
+
+  void fetchDescendants();
+  enum class DescendantLoad { Failed, Success };
+  void notifyOneDescendantFinished(DescendantLoad wasSuccess);
+
+  void instantiate();
+  HeapHashSet<Member<ModuleScript>> uninstantiatedInclusiveDescendants();
+
+  class DependencyModuleClient;
+  friend class DependencyModuleClient;
+
+  Member<Modulator> m_modulator;
+  Member<ModuleTreeLinkerRegistry> m_registry;
+  Member<ModuleTreeClient> m_client;
+  HashSet<KURL> m_ancestorListWithUrl;
+  State m_state = State::Initial;
+  Member<ModuleScript> m_moduleScript;
+  size_t m_numIncompleteDescendants = 0;
+  HeapHashSet<Member<DependencyModuleClient>> m_dependencyClients;
+};
+
+}  // namespace blink
+
+#endif