Add env var to allow keeping the existent navigation on a fragment load

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: magomez

Source/WebCore/loader/FrameLoader.cpp

@@ -1638,15 +1638,38 @@ void FrameLoader::loadURL(FrameLoadRequest&& frameLoadRequest, const String& ref
 
         if (!dispatchNavigateEvent(newURL, newLoadType, action.downloadAttribute(), historyHandling, true))
             return;
+        static bool keepNavigationOnFragmentLoad = false;
+        static bool keepNavigationOnFragmentLoadInitialized = false;
+
+        if (!keepNavigationOnFragmentLoadInitialized) {
+            keepNavigationOnFragmentLoad = !!getenv("WPE_KEEP_NAVIGATION_ON_FRAGMENT_LOAD");
+            keepNavigationOnFragmentLoadInitialized = true;
+        }
 
         oldDocumentLoader->setTriggeringAction(WTFMove(action));
         oldDocumentLoader->setLastCheckedRequest(ResourceRequest());
-        policyChecker().stopCheck();
+        auto loadType = policyChecker().loadType();
+        bool resetLoadTypeAfterFragmentNavigation = false;
+        if (keepNavigationOnFragmentLoad && ((m_policyDocumentLoader && !equalIgnoringFragmentIdentifier(m_policyDocumentLoader->request().url(), frameLoadRequest.resourceRequest().url())) || (m_provisionalDocumentLoader && !equalIgnoringFragmentIdentifier(m_provisionalDocumentLoader->request().url(), frameLoadRequest.resourceRequest().url())))) {
+            resetLoadTypeAfterFragmentNavigation = true;
+
+            const auto fragmentNavigationURL = frameLoadRequest.resourceRequest().url();
+            const auto navigationURL = m_policyDocumentLoader ? m_policyDocumentLoader->request().url(): m_provisionalDocumentLoader->request().url();
+            FRAMELOADER_RELEASE_LOG(ResourceLoading, "loadURL: navigation to: %s will be continued after fragment navigation to url: %s",
+                navigationURL.string().utf8().data(), fragmentNavigationURL.string().utf8().data());
+        } else {
+            policyChecker().stopCheck();
+        }
+
         policyChecker().setLoadType(newLoadType);
         RELEASE_ASSERT(!isBackForwardLoadType(newLoadType) || history().provisionalItem());
         policyChecker().checkNavigationPolicy(WTFMove(request), ResourceResponse { } /* redirectResponse */, oldDocumentLoader.get(), WTFMove(formState), [this, protectedThis = Ref { *this }, requesterOrigin = Ref { frameLoadRequest.requesterSecurityOrigin() }, historyHandling] (const ResourceRequest& request, WeakPtr<FormState>&&, NavigationPolicyDecision navigationPolicyDecision) {
             continueFragmentScrollAfterNavigationPolicy(request, requesterOrigin.ptr(), navigationPolicyDecision == NavigationPolicyDecision::ContinueLoad, historyHandling);
         }, PolicyDecisionMode::Synchronous);
+
+        if (resetLoadTypeAfterFragmentNavigation)
+            policyChecker().setLoadType(loadType);
+
         return;
     }
 
@@ -3716,8 +3739,16 @@ void FrameLoader::continueFragmentScrollAfterNavigationPolicy(const ResourceRequ
     // frame to be deallocated.
     Ref frame = m_frame.get();
 
+    static bool keepNavigationOnFragmentLoad = false;
+    static bool keepNavigationOnFragmentLoadInitialized = false;
+
+    if (!keepNavigationOnFragmentLoadInitialized) {
+        keepNavigationOnFragmentLoad = !!getenv("WPE_KEEP_NAVIGATION_ON_FRAGMENT_LOAD");
+        keepNavigationOnFragmentLoadInitialized = true;
+    }
+
     // If we have a provisional request for a different document, a fragment scroll should cancel it.
-    if (m_provisionalDocumentLoader && !equalIgnoringFragmentIdentifier(m_provisionalDocumentLoader->request().url(), request.url())) {
+    if (m_provisionalDocumentLoader && !equalIgnoringFragmentIdentifier(m_provisionalDocumentLoader->request().url(), request.url()) && !keepNavigationOnFragmentLoad) {
         protectedProvisionalDocumentLoader()->stopLoading();
         FRAMELOADER_RELEASE_LOG(ResourceLoading, "continueFragmentScrollAfterNavigationPolicy: Clearing provisional document loader (m_provisionalDocumentLoader=%p)", m_provisionalDocumentLoader.get());
         setProvisionalDocumentLoader(nullptr);

Source/WebCore/loader/PolicyChecker.cpp

@@ -292,6 +292,10 @@ void PolicyChecker::checkNavigationPolicy(ResourceRequest&& request, const Resou
     }
 
     auto documentLoader = frameLoader->loaderForWebsitePolicies();
+    // PolicyDecisionMode::Synchronous means that it is a FragmentNavigation and in that case we should use documentLoader,
+    // because there can be ongoing (in policy or provisional state) navigation.
+    if (policyDecisionMode == PolicyDecisionMode::Synchronous)
+        documentLoader = frameLoader->documentLoader();
     auto clientRedirectSourceForHistory = documentLoader ? documentLoader->clientRedirectSourceForHistory() : String();
     auto navigationID = documentLoader ? documentLoader->navigationID() : std::nullopt;
     bool hasOpener = !!frame->opener();