Bug 1603542 - Log a warning in the web console when a preloaded resource is not used, r=Harald

Differential Revision: https://phabricator.services.mozilla.com/D76527

dom/locales/en-US/chrome/dom/dom.properties

@@ -389,3 +389,5 @@ WebShareAPI_Aborted=The share operation was aborted.
 # LOCALIZATION NOTE (UnknownProtocolNavigationPrevented): %1$S is the destination URL.
 UnknownProtocolNavigationPrevented=Prevented navigation to “%1$S” due to an unknown protocol.
 PostMessageSharedMemoryObjectToCrossOriginWarning=Cannot post message containing a shared memory object to a cross-origin window.
+# LOCALIZATION NOTE: %S is the URL of the resource in question
+UnusedLinkPreloadPending=The resource at “%S” preloaded with link preload was not used within a few seconds. Make sure all attributes of the preload tag are set correctly.

uriloader/preload/PreloaderBase.cpp

@@ -5,6 +5,7 @@
 #include "PreloaderBase.h"
 
 #include "mozilla/dom/Document.h"
+#include "nsContentUtils.h"
 #include "nsIAsyncVerifyRedirectCallback.h"
 #include "nsIChannel.h"
 #include "nsILoadGroup.h"
@@ -111,7 +112,9 @@ void PreloaderBase::NotifyOpen(const PreloadHashKey& aKey, nsIChannel* aChannel,
   NotifyOpen(aKey, aDocument, aIsPreload);
   mChannel = aChannel;
 
-  // * Start the usage timer if aIsPreload.
+  auto callback = MakeRefPtr<UsageTimer>(this, aDocument);
+  NS_NewTimerWithCallback(getter_AddRefs(mUsageTimer), callback, 10000,
+                          nsITimer::TYPE_ONE_SHOT);
 
   nsCOMPtr<nsIInterfaceRequestor> callbacks;
   mChannel->GetNotificationCallbacks(getter_AddRefs(callbacks));
@@ -146,8 +149,7 @@ void PreloaderBase::NotifyUsage(LoadBackground aLoadBackground) {
   }
 
   mIsUsed = true;
-
-  // * Cancel the usage timer.
+  CancelUsageTimer();
 }
 
 void PreloaderBase::RemoveSelf(dom::Document* aDocument) {
@@ -161,6 +163,8 @@ void PreloaderBase::NotifyRestart(dom::Document* aDocument,
   RemoveSelf(aDocument);
   mKey = PreloadHashKey();
 
+  CancelUsageTimer();
+
   if (aNewPreloader) {
     aNewPreloader->mNodes = std::move(mNodes);
   }
@@ -254,6 +258,13 @@ void PreloaderBase::NotifyNodeEvent(nsINode* aNode) {
       aNode, mShouldFireLoadEvent || NS_SUCCEEDED(*mOnStopStatus));
 }
 
+void PreloaderBase::CancelUsageTimer() {
+  if (mUsageTimer) {
+    mUsageTimer->Cancel();
+    mUsageTimer = nullptr;
+  }
+}
+
 nsresult PreloaderBase::AsyncConsume(nsIStreamListener* aListener) {
   // We want to return an error so that consumers can't ever use a preload to
   // consume data unless it's properly implemented.
@@ -275,4 +286,38 @@ nsCString PreloaderBase::RedirectRecord::Fragment() const {
   return fragment;
 }
 
+// PreloaderBase::UsageTimer
+
+NS_IMPL_ISUPPORTS(PreloaderBase::UsageTimer, nsITimerCallback)
+
+NS_IMETHODIMP PreloaderBase::UsageTimer::Notify(nsITimer* aTimer) {
+  if (!mPreload || !mDocument) {
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(aTimer == mPreload->mUsageTimer);
+  mPreload->mUsageTimer = nullptr;
+
+  if (mPreload->IsUsed()) {
+    // Left in the hashtable, but marked as used.  This is a valid case, and we
+    // don't want to emit a warning for this preload then.
+    return NS_OK;
+  }
+
+  // PreloadHashKey overrides GetKey, we need to use the nsURIHashKey one to get
+  // the URI.
+  nsIURI* uri = static_cast<nsURIHashKey*>(&mPreload->mKey)->GetKey();
+  if (!uri) {
+    return NS_OK;
+  }
+  nsString spec = NS_ConvertUTF8toUTF16(uri->GetSpecOrDefault());
+
+  nsContentUtils::ReportToConsole(
+      nsIScriptError::warningFlag, NS_LITERAL_CSTRING("DOM"), mDocument,
+      nsContentUtils::eDOM_PROPERTIES, "UnusedLinkPreloadPending",
+      nsTArray<nsString>({spec}));
+
+  return NS_OK;
+}
+
 }  // namespace mozilla

uriloader/preload/PreloaderBase.h

@@ -11,6 +11,7 @@
 #include "nsIChannelEventSink.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsIRedirectResultListener.h"
+#include "nsITimer.h"
 #include "nsIURI.h"
 #include "nsTArray.h"
 #include "nsProxyRelease.h"
@@ -141,6 +142,7 @@ class PreloaderBase : public SupportsWeakPtr<PreloaderBase>,
 
  private:
   void NotifyNodeEvent(nsINode* aNode);
+  void CancelUsageTimer();
 
   // A helper class that will update the PreloaderBase.mChannel member when a
   // redirect happens, so that we can reprioritize or cancel when needed.
@@ -168,6 +170,21 @@ class PreloaderBase : public SupportsWeakPtr<PreloaderBase>,
     nsCOMPtr<nsIChannel> mRedirectChannel;
   };
 
+  // A timer callback to trigger the unuse warning for this preload
+  class UsageTimer final : public nsITimerCallback {
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSITIMERCALLBACK
+
+    UsageTimer(PreloaderBase* aPreload, dom::Document* aDocument)
+        : mDocument(aDocument), mPreload(aPreload) {}
+
+   private:
+    ~UsageTimer() = default;
+
+    WeakPtr<dom::Document> mDocument;
+    WeakPtr<PreloaderBase> mPreload;
+  };
+
  private:
   // Reference to HTMLLinkElement DOM nodes to deliver onload and onerror
   // notifications to.
@@ -176,6 +193,10 @@ class PreloaderBase : public SupportsWeakPtr<PreloaderBase>,
   // History of redirects.
   nsTArray<RedirectRecord> mRedirectRecords;
 
+  // Usage timer, emits warning when the preload is not used in time.  Started
+  // in NotifyOpen and stopped in NotifyUsage.
+  nsCOMPtr<nsITimer> mUsageTimer;
+
   // The key this preload has been registered under.  We want to remember it to
   // be able to deregister itself from the document's preloads.
   PreloadHashKey mKey;