Fragment navigation should be cancelled if there is ongoing navigation

Fragment navigation is synchronous, while navigation is asynchronous.
It can happen that fragment navigation starts when navigation is in
the policy or provisional step of loading. In that case, we should
cancel the requested fragment navigation and make the navigation finish.

Author: pgorszkowski-igalia

Source/WebCore/loader/FrameLoader.cpp

@@ -1482,6 +1482,23 @@ void FrameLoader::loadURL(FrameLoadRequest&& frameLoadRequest, const String& ref
     if (m_inStopAllLoaders || m_inClearProvisionalLoadForPolicyCheck)
         return;
 
+    static bool keepNavigationOnFragmentLoad = false;
+    static bool keepNavigationOnFragmentLoadInitialized = false;
+
+    if (!keepNavigationOnFragmentLoadInitialized) {
+        keepNavigationOnFragmentLoad = !!getenv("WPE_KEEP_NAVIGATION_ON_FRAGMENT_LOAD");
+        keepNavigationOnFragmentLoadInitialized = true;
+    }
+
+    // If we have a policy or provisional request for a different document, a fragment scroll should be cancelled.
+    if (keepNavigationOnFragmentLoad && (m_policyDocumentLoader && !equalIgnoringFragmentIdentifier(m_policyDocumentLoader->request().url(), frameLoadRequest.resourceRequest().url()) ||
+                                         m_provisionalDocumentLoader && !equalIgnoringFragmentIdentifier(m_provisionalDocumentLoader->request().url(), frameLoadRequest.resourceRequest().url()))) {
+        const auto fragmentNavigationURL = frameLoadRequest.resourceRequest().url();
+        const auto navigationURL = m_policyDocumentLoader ? m_policyDocumentLoader->request().url(): m_provisionalDocumentLoader->request().url();
+        FRAMELOADER_RELEASE_LOG(ResourceLoading, "loadURL: fragment navigation: %s is cancelled because of ongoing navigation change to url: %s", fragmentNavigationURL.string().utf8().data(), navigationURL.string().utf8().data());
+        return;
+    }
+
     Ref frame = m_frame.get();
 
     // Anchor target is ignored when the download attribute is set since it will download the hyperlink rather than follow it.