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

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

Index: third_party/WebKit/Source/core/dom/ModuleMap.cpp
diff --git a/third_party/WebKit/Source/core/dom/ModuleMap.cpp b/third_party/WebKit/Source/core/dom/ModuleMap.cpp
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index 0000000000000000000000000000000000000000..9f726a3062f85f82bba87b6664f6298e62c3a90c
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+++ b/third_party/WebKit/Source/core/dom/ModuleMap.cpp
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+// 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.
+
+#include "bindings/core/v8/V8PerIsolateData.h"
+#include "core/dom/ModuleMap.h"
+#include "core/fetch/ResourceFetcher.h"
+#include "core/frame/LocalFrame.h"
+#include "platform/network/mime/MIMETypeRegistry.h"
+#include "wtf/AutoReset.h"
+#include <v8.h>
+
+namespace blink {
+
+LocalFrame* g_localFrame = nullptr;
+
+ModuleLoaderClient::~ModuleLoaderClient() {}
+
+void ModuleLoaderClient::catchUpToLatestStateIfNeeded(
+    ModuleLoaderState latestState) {
+  if (m_state == ModuleLoaderState::Finished)
+    return;
+  if (latestState == ModuleLoaderState::Finished) {
+    notifyFinished();
+    m_state = latestState;
+  }
+}
+
+ModuleLoader::ModuleLoader(const KURL& url) : m_url(url) {}
+
+ModuleLoader::~ModuleLoader() {}
+
+void ModuleLoader::advanceState(ModuleLoaderState newState) {

[dominicc (has gone to gerrit), 2016/12/13 07:45:29]

+1 to simple state machines with assertions on the transitions.

+  switch (m_state) {
+    case ModuleLoaderState::Initial:
+      DCHECK_EQ(newState, ModuleLoaderState::Fetching);
+      break;
+    case ModuleLoaderState::Fetching:
+      DCHECK_EQ(newState, ModuleLoaderState::Finished);
+      break;
+    case ModuleLoaderState::Finished:
+    default:
+      NOTREACHED();
+  }
+  m_state = newState;
+
+  notifyAndFlushPendingClients();
+}
+
+void ModuleLoader::fetch(ResourceFetcher* fetcher) {
+  // Step 4. Set moduleMap[url] to "fetching".
+  advanceState(ModuleLoaderState::Fetching);
+
+  // Step 5. Let request be a new request whose url is url, destination is
+  // destination, type is "script", mode is "cors", credentials mode is
+  // credentials mode, cryptographic nonce metadata is cryptographic nonce,
+  // parser metadata is parser state, referrer is referrer, and client is fetch
+  // client settings object.
+  FetchRequest request(ResourceRequest(m_url), "module");
+  // request.setDefer(FetchRequest::LazyLoad); //? always async -> defer?
+  Member<ScriptResource> resource = ScriptResource::fetch(request, fetcher);
+  setResource(resource);
+
+  // Step 6. If the caller specified custom steps to perform the fetch, perform
+  // them on request, setting the is top-level flag if the top-level module
+  // fetch flag is set. Return from this algorithm, and when the custom perform
+  // the fetch steps complete with response response, run the remaining steps.
+  // Otherwise, fetch request. Return from this algorithm, and run the remaining
+  // steps as part of the fetch's process response for the response response.
+  // Note: response is always CORS-same-origin.
+
+  // TODO(kouhei): I don't know what Step 6 means. ScriptLoader seems to ignore
+  // the step?
+}
+
+bool ModuleLoader::wasModuleLoadSuccessful(Resource* resource) {
+  // Implements conditions in Step 7 of
+  // https://html.spec.whatwg.org/#fetch-a-single-module-script
+
+  // - response's type is "error"
+  if (resource->errorOccurred())
+    return false;
+
+  const auto& response = resource->response();
+  // - response's status is not an ok status
+  if (response.isHTTP() &&
+      (response.httpStatusCode() < 200 || response.httpStatusCode() >= 300)) {
+    return false;
+  }
+
+  // The result of extracting a MIME type from response's header list
+  // (ignoring parameters) is not a JavaScript MIME type
+  // Note: For historical reasons, fetching a classic script does not include
+  // MIME type checking. In contrast, module scripts will fail to load if they
+  // are not of a correct MIME type.
+  if (!MIMETypeRegistry::isSupportedJavaScriptMIMEType(response.mimeType()))
+    return false;
+
+  return true;
+}
+
+void ModuleLoader::notifyFinished(Resource*) {
+  printf("notifyFinished!\n");
+
+  // Note: "conditions" referred in Step 7 is implemented in
+  // wasModuleLoadSuccessful().
+  // Step 7. If any of the following conditions are met, set moduleMap[url] to
+  // null, asynchronously complete this algorithm with null, and abort these
+  // steps.
+  if (!wasModuleLoadSuccessful(resource())) {
+    printf("notifyFinished but load was not successful\n");
+
+    m_wasLoadSuccessful = false;
+    advanceState(ModuleLoaderState::Finished);
+    setResource(nullptr);
+    return;
+  }
+
+  // Step 8. Let source text be the result of UTF-8 decoding response's body.
+  String script = resource()->script();
+  printf("fetched script: %s\n", script.utf8().data());
+
+  // Step 9. Let module script be the result of creating a module script given
+  // source text, module map settings object, response's url, cryptographic
+  // nonce, parser state, and credentials mode.
+  v8::Isolate* isolate = V8PerIsolateData::mainThreadIsolate();
+  v8::HandleScope handleScope(isolate);
+
+  ScriptState* scriptState = ScriptState::forMainWorld(g_localFrame);
+  DCHECK(scriptState);
+
+  // ??? : I'm not sure why this requres scriptState to run compile step.
+  ScriptState::Scope scope(scriptState);
+  m_scriptModule = ScriptModule::compile(isolate, script, m_url.getString());
+
+  m_wasLoadSuccessful = true;
+  advanceState(ModuleLoaderState::Finished);
+  setResource(nullptr);
+}
+
+void ModuleLoader::addClient(ModuleLoaderClient* newClient) {
+  DCHECK(!m_pendingClients.contains(newClient));
+  DCHECK(!m_clients.contains(newClient));
+  newClient->setLoader(this);
+  m_pendingClients.add(newClient);
+
+  notifyAndFlushPendingClients();
+}
+
+void ModuleLoader::notifyAndFlushPendingClients() {
+  if (m_isFlushingPendingClients) {
+    // This notifyAndFlushPendingClients call was reentrant.
+    // Defer to first notifyAndFlushPendingClients to do the job.
+    return;
+  }
+
+  AutoReset<bool> forbidClientModificationScope(&m_isFlushingPendingClients,
+                                                true);
+
+  if (m_lastClientNotifiedState != m_state) {
+    // if m_state has changed since last update, put all m_clients back into
+    // m_pendingClients so that they catchUpToLatestStateIfNeeded()
+    m_pendingClients.swap(m_clients);
+    while (!m_clients.isEmpty()) {
+      m_pendingClients.add(m_clients.takeAny());
+    }
+
+    m_lastClientNotifiedState = m_state;
+  }
+
+  while (!m_pendingClients.isEmpty()) {
+    // Iterate on copy as m_pendingClients may be added in the notification
+    // loop.
+    HeapHashSet<Member<ModuleLoaderClient>> clientsToCatchUp;
+    clientsToCatchUp.swap(m_pendingClients);
+    for (const auto& client : clientsToCatchUp) {
+      client->catchUpToLatestStateIfNeeded(m_state);
+    }
+
+    // Caught up clients do not have any notifications to receive after the
+    // load is finished.
+    if (hasFinished())
+      continue;
+
+    while (!clientsToCatchUp.isEmpty())
+      m_clients.add(clientsToCatchUp.takeAny());
+  }
+}
+
+DEFINE_TRACE(ModuleLoader) {
+  visitor->trace(m_pendingClients);
+  visitor->trace(m_clients);
+  ResourceOwner<ScriptResource>::trace(visitor);
+}
+
+ModuleMap::ModuleMap(LocalFrame* frame, ResourceFetcher* fetcher)
+    : m_frame(frame), m_fetcher(fetcher) {
+  DCHECK(m_frame);
+  DCHECK(m_fetcher);
+}
+
+void ModuleMap::fetch(const KURL& url, ModuleLoaderClient* client) {
+  g_localFrame = m_frame;  // TODO(kouhei): AAAAAAAArrrrrgghhh
+  printf("ModuleMap::fetch(%s)\n", url.getString().utf8().data());
+
+  MapImpl::AddResult result = m_map.set(url, nullptr);
+  Member<ModuleLoader>& loaderEntry = result.storedValue->value;
+  if (!result.isNewEntry) {
+    printf("not new entry\n");
+
+    // - If moduleMap[url] is "fetching", wait (in parallel) until that
+    // loaderEntry's value changes, then proceed to the next step.
+    // - If moduleMap[url] exists, asynchronously complete this algorithm
+    // with moduleMap[url], and abort these steps.
+    loaderEntry->addClient(client);
+    return;
+  }
+
+  ModuleLoader* loader = ModuleLoader::create(url);
+  loader->fetch(m_fetcher.get());
+
+  // Step 10. Set moduleMap[url] to module script, and asynchronously complete
+  // this algorithm with module script.
+  loaderEntry = loader;
+  loaderEntry->addClient(client);
+}
+
+DEFINE_TRACE(ModuleMap) {
+  visitor->trace(m_map);
+  visitor->trace(m_frame);
+  visitor->trace(m_fetcher);
+}
+
+}  // namespace blink