[Layered API] Disable fallback syntax

Bug: 864748, 829084
Change-Id: I164d3a83345ca9fe02a31f6a09d7fc646299a436
Reviewed-on: https://chromium-review.googlesource.com/1141105Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584077}

third_party/blink/renderer/core/loader/modulescript/module_tree_linker.cc

@@ -163,10 +163,8 @@ void ModuleTreeLinker::FetchRoot(const KURL& original_url,
   // href="https://github.com/drufball/layered-apis/blob/master/spec.md#fetch-a-module-script-graph"
   // step="1">Set url to the layered API fetching URL given url and the current
   // settings object's API base URL.</spec>
-  if (RuntimeEnabledFeatures::LayeredAPIEnabled()) {
-    url = blink::layered_api::ResolveFetchingURL(
-        url, fetch_client_settings_object_->BaseURL());
-  }
+  if (RuntimeEnabledFeatures::LayeredAPIEnabled())
+    url = blink::layered_api::ResolveFetchingURL(url);
 
 #if DCHECK_IS_ON()
   url_ = url;

third_party/blink/renderer/core/script/layered_api.cc

@@ -60,7 +60,7 @@ bool IsImplemented(const String& name) {
 }  // namespace
 
 // https://github.com/drufball/layered-apis/blob/master/spec.md#user-content-layered-api-fetching-url
-KURL ResolveFetchingURL(const KURL& url, const KURL& base_url) {
+KURL ResolveFetchingURL(const KURL& url) {
   // <spec step="1">If url's scheme is not "std", return url.</spec>
   if (!url.ProtocolIs(kStdScheme))
     return url;
@@ -68,39 +68,18 @@ KURL ResolveFetchingURL(const KURL& url, const KURL& base_url) {
   // <spec step="2">Let path be url's path[0].</spec>
   const String path = url.GetPath();
 
-  // <spec step="3">Let identifier be the portion of path before the first
-  // U+007C (|), or all of path if no U+007C is present.</spec>
-  //
-  // <spec step="4">Let fallback be the portion of path after the first U+007C,
-  // or null if no U+007C is present.</spec>
-  String identifier;
-  String fallback;
-  const size_t separator_position = path.find('|');
-  if (separator_position != WTF::kNotFound) {
-    identifier = path.Substring(0, separator_position);
-    fallback = path.Substring(separator_position + 1);
-  } else {
-    identifier = path;
-  }
-
   // <spec step="5">If the layered API identified by path is implemented by this
   // user agent, return the result of parsing the concatenation of "std:" with
   // identifier.</spec>
-  if (IsImplemented(identifier)) {
+  if (IsImplemented(path)) {
     StringBuilder url_string;
     url_string.Append(kStdScheme);
     url_string.Append(":");
-    url_string.Append(identifier);
+    url_string.Append(path);
     return KURL(NullURL(), url_string.ToString());
   }
 
-  // <spec step="6">If fallback is null, return failure.</spec>
-  if (fallback.IsNull())
-    return NullURL();
-
-  // <spec step="7">Return the result of parsing fallback with the base URL
-  // baseURLForFallback.</spec>
-  return KURL(base_url, fallback);
+  return NullURL();
 }
 
 KURL GetInternalURL(const KURL& url) {

third_party/blink/renderer/core/script/layered_api.h

@@ -17,11 +17,11 @@ namespace blink {
 // https://docs.google.com/document/d/1V-WaCZQbBcQJRSYSYBb8Y6p0DOdDpiNDSmD41ui_73s/edit
 namespace layered_api {
 
-// <spec
-// href="https://github.com/drufball/layered-apis/blob/master/spec.md#user-content-layered-api-fetching-url">
-// This operation maps URLs of the form std:x|y to either std:x or y
-// URLs.</spec>
-CORE_EXPORT KURL ResolveFetchingURL(const KURL&, const KURL& base_url);
+// https://github.com/drufball/layered-apis/blob/master/spec.md#user-content-layered-api-fetching-url
+//
+// Currently fallback syntax is disabled and only "std:x" (not "std:x|y") is
+// accepted. https://crbug.com/864748
+CORE_EXPORT KURL ResolveFetchingURL(const KURL&);
 
 // Returns std-internal://x/index.js if the URL is Layered API, or null URL
 // otherwise (not specced).

third_party/blink/renderer/core/script/layered_api_test.cc

@@ -15,31 +15,17 @@ namespace {
 TEST(LayeredAPITest, ResolveFetchingURL) {
   KURL base_url("https://example.com/base/path/");
 
-  EXPECT_EQ(ResolveFetchingURL(KURL("https://example.com/"), base_url),
+  EXPECT_EQ(ResolveFetchingURL(KURL("https://example.com/")),
             KURL("https://example.com/"));
 
-  EXPECT_EQ(ResolveFetchingURL(KURL("std:blank"), base_url), KURL("std:blank"));
-  EXPECT_EQ(ResolveFetchingURL(KURL("std:blank|https://fallback.example.com/"),
-                               base_url),
-            KURL("std:blank"));
-  EXPECT_EQ(
-      ResolveFetchingURL(KURL("std:blank|https://:invalid-url"), base_url),
-      KURL("std:blank"));
-
-  EXPECT_EQ(ResolveFetchingURL(KURL("std:none"), base_url), NullURL());
-  EXPECT_EQ(ResolveFetchingURL(KURL("std:none|https://fallback.example.com/"),
-                               base_url),
-            KURL("https://fallback.example.com/"));
-  EXPECT_FALSE(
-      ResolveFetchingURL(KURL("std:none|https://:invalid-url"), base_url)
-          .IsValid());
-
-  EXPECT_EQ(ResolveFetchingURL(KURL("std:none|fallback.js"), base_url),
-            KURL("https://example.com/base/path/fallback.js"));
-  EXPECT_EQ(ResolveFetchingURL(KURL("std:none|./fallback.js"), base_url),
-            KURL("https://example.com/base/path/fallback.js"));
-  EXPECT_EQ(ResolveFetchingURL(KURL("std:none|/fallback.js"), base_url),
-            KURL("https://example.com/fallback.js"));
+  EXPECT_EQ(ResolveFetchingURL(KURL("std:blank")), KURL("std:blank"));
+
+  EXPECT_EQ(ResolveFetchingURL(KURL("std:none")), NullURL());
+
+  // Fallback syntax is currently disabled and rejected.
+  // https://crbug.com/864748
+  EXPECT_EQ(ResolveFetchingURL(KURL("std:blank|https://example.com/")),
+            NullURL());
 }
 
 TEST(LayeredAPITest, GetInternalURL) {

third_party/blink/renderer/core/script/modulator_impl_base.cc

@@ -121,7 +121,7 @@ KURL ModulatorImplBase::ResolveModuleSpecifier(const String& module_request,
     // specifier. If parsed is not failure, then return the layered API fetching
     // URL given parsed and script's base URL.</spec>
     if (RuntimeEnabledFeatures::LayeredAPIEnabled())
-      return blink::layered_api::ResolveFetchingURL(url, base_url);
+      return blink::layered_api::ResolveFetchingURL(url);
 
     return url;
   }