[POC] Implement "module responses map" concept

third_party/WebKit/Source/core/loader/modulescript/ModuleScriptFetcher.cpp

Index: third_party/WebKit/Source/core/loader/modulescript/ModuleScriptFetcher.cpp
diff --git a/third_party/WebKit/Source/core/loader/modulescript/ModuleScriptFetcher.cpp b/third_party/WebKit/Source/core/loader/modulescript/ModuleScriptFetcher.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..98dd7f5d39b084009037fdbc7ac6777d84d845f7
--- /dev/null
+++ b/third_party/WebKit/Source/core/loader/modulescript/ModuleScriptFetcher.cpp
@@ -0,0 +1,122 @@
+// 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.
+
+#include "core/loader/modulescript/ModuleScriptFetcher.h"
+
+#include "core/dom/ExecutionContext.h"
+#include "core/inspector/ConsoleMessage.h"
+#include "core/loader/modulescript/ModuleScriptLoader.h"
+#include "platform/loader/fetch/FetchUtils.h"
+#include "platform/network/mime/MIMETypeRegistry.h"
+
+namespace blink {
+
+namespace {
+
+bool WasModuleLoadSuccessful(Resource* resource,
+                             ConsoleMessage** error_message) {
+  // Implements conditions in Step 7 of
+  // https://html.spec.whatwg.org/#fetch-a-single-module-script
+
+  // - response's type is "error"
+  if (!resource || resource->ErrorOccurred()) {
+    return false;
+  }
+
+  const auto& response = resource->GetResponse();
+  // - response's status is not an ok status
+  if (response.IsHTTP() && !FetchUtils::IsOkStatus(response.HttpStatusCode())) {
+    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.
+  // We use ResourceResponse::httpContentType() instead of mimeType(), as
+  // mimeType() may be rewritten by mime sniffer.
+  if (!MIMETypeRegistry::IsSupportedJavaScriptMIMEType(
+          response.HttpContentType())) {
+    if (error_message) {
+      String message =
+          "Failed to load module script: The server responded with a "
+          "non-JavaScript MIME type of \"" +
+          response.HttpContentType() +
+          "\". Strict MIME type checking is enforced for module scripts per "
+          "HTML spec.";
+      *error_message = ConsoleMessage::CreateForRequest(
+          kJSMessageSource, kErrorMessageLevel, message,
+          response.Url().GetString(), resource->Identifier());
+    }
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace
+
+ModuleScriptFetcher::ModuleScriptFetcher(FetchParameters fetch_params,
+                                         ResourceFetcher* fetcher,
+                                         Modulator* modulator)
+    : fetch_params_(fetch_params), fetcher_(fetcher), modulator_(modulator) {}
+
+void ModuleScriptFetcher::Fetch(ModuleScriptLoader* loader) {
+  loader_ = loader;
+  FetchInternal();
+}
+
+void ModuleScriptFetcher::NotifyFinished(Resource* resource) {
+  ClearResource();
+
+  ScriptResource* script_resource = ToScriptResource(resource);
+  ConsoleMessage* error_message = nullptr;
+  if (!WasModuleLoadSuccessful(script_resource, &error_message)) {
+    if (error_message) {
+      ExecutionContext::From(modulator_->GetScriptState())
+          ->AddConsoleMessage(error_message);
+    }
+    Finalize(WTF::nullopt);
+    return;
+  }
+
+  ModuleScriptCreationParams params(
+      script_resource->GetResponse().Url(), script_resource->SourceText(),
+      script_resource->GetResourceRequest().GetFetchCredentialsMode(),
+      script_resource->CalculateAccessControlStatus());
+  Finalize(params);
+}
+
+void ModuleScriptFetcher::FetchInternal() {
+  ScriptResource* resource = ScriptResource::Fetch(fetch_params_, fetcher_);
+  if (was_fetched_) {
+    // ScriptResource::fetch() has succeeded synchronously,
+    // ::notifyFinished() already took care of the |resource|.
+    return;
+  }
+  if (!resource) {
+    // ScriptResource::fetch() has failed synchronously.
+    NotifyFinished(nullptr);
+    return;
+  }
+
+  // ScriptResource::fetch() is processed asynchronously.
+  SetResource(resource);
+}
+
+void ModuleScriptFetcher::Finalize(
+    WTF::Optional<ModuleScriptCreationParams> params) {
+  was_fetched_ = true;
+  loader_->NotifyFetchFinished(params);
+}
+
+DEFINE_TRACE(ModuleScriptFetcher) {
+  visitor->Trace(fetcher_);
+  visitor->Trace(modulator_);
+  visitor->Trace(loader_);
+  ResourceOwner<ScriptResource>::Trace(visitor);
+}
+
+}  // namespace blink