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

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

+// 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 "core/dom/ModuleMap.h"
+#include "core/fetch/ResourceFetcher.h"
+#include "core/loader/resource/ScriptResource.h"
+
+namespace blink {
+
+ModuleMap::ModuleMap(ResourceFetcher* fetcher)
+  : m_fetcher(fetcher)
+{
+  DCHECK(m_fetcher);
+}
+
+void ModuleMap::fetch(const KURL& url) {
+  printf("ModuleMap::fetch(%s)\n", url.getString().utf8().data());
+
+  MapImpl::AddResult result = m_map.set(url, Entry());
+  Entry& entry = result.storedValue->value;
+  if (!result.isNewEntry) {
+    printf("not new entry\n");
+    // FIXME: If moduleMap[url] is "fetching", wait (in parallel) until that
+    // entry's value changes, then proceed to the next step.
+    if (entry.isFetching()) {
+      // return promise?
+    }
+    // FIXME: If moduleMap[url] exists, asynchronously complete this algorithm
+    // with moduleMap[url], and abort these steps.
+    return;
+  }
+
+  // Step 4. Set moduleMap[url] to "fetching". => Initial entry state is
+  // 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(url), "module");
+  // request.setDefer(FetchRequest::LazyLoad); //? always async -> defer?
+  Member<ScriptResource> resource = ScriptResource::fetch(request, m_fetcher.get());
+  resource->script();
+
+  // 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): yokuwakaran
+
+  // 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:
+  // - response's type is "error"
+  // - response's status is not an ok status
+  // 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.
+
+  // Step 8. Let source text be the result of UTF-8 decoding response's body.
+
+  // 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.
+
+  // Step 10. Set moduleMap[url] to module script, and asynchronously complete
+  // this algorithm with module script.
+}
+
+DEFINE_TRACE(ModuleMap) {
+  visitor->trace(m_map);
+  visitor->trace(m_fetcher);
+}
+
+}  // namespace blink