fix: render React layout on Flow -> Flow navigation

flow-server/src/main/java/com/vaadin/flow/component/UI.java

@@ -1694,6 +1694,7 @@ public List<HasElement> getActiveRouterTargetsChain() {
     private boolean navigationInProgress = false;
 
     private String forwardToClientUrl = null;
+    private boolean serverForwarded = false;
 
     private boolean firstNavigation = true;
 
@@ -1847,9 +1848,13 @@ public void browserNavigate(BrowserNavigateEvent event) {
         } else if (isPostponed()) {
             serverPaused();
         } else {
-            // acknowledge client, but cancel if session not open
-            serverConnected(
-                    !getSession().getState().equals(VaadinSessionState.OPEN));
+            if (!firstNavigation && serverForwarded) {
+                cancelClient();
+            } else {
+                // acknowledge client, but cancel if session not open
+                serverConnected(!getSession().getState()
+                        .equals(VaadinSessionState.OPEN));
+            }
             replaceStateIfDiffersAndNoReplacePending(event.route, location);
         }
     }
@@ -1869,11 +1874,18 @@ private void replaceStateIfDiffersAndNoReplacePending(String route,
                 .containsPendingJavascript("window.history.replaceState")) {
             // See InternalRedirectHandler invoked via Router.
             getPage().getHistory().replaceState(null, location);
+            // getPage().executeJs(
+            // "setTimeout(() => { window.history.replaceState($0, '', $1);})",
+            // null,
+            // Optional.ofNullable(location)
+            // .map(Location::getPathWithQueryParameters)
+            // .map(path -> path.isEmpty() ? "." : path)
+            // .orElse(null));
         }
     }
 
     /**
-     * Check that the view can be leave. This method is invoked when the client
+     * Check that the view can be left. This method is invoked when the client
      * router tries to navigate to a client route while the current route is a
      * server route.
      * <p>
@@ -2000,7 +2012,7 @@ private void handleNavigation(Location location,
 
             forwardToClientUrl = clientNavigationStateRenderer
                     .getClientForwardRoute();
-
+            serverForwarded = clientNavigationStateRenderer.isServerForwarded();
             adjustPageTitle();
 
         } catch (Exception exception) {

flow-server/src/main/java/com/vaadin/flow/component/internal/JavaScriptNavigationStateRenderer.java

@@ -46,6 +46,7 @@ public class JavaScriptNavigationStateRenderer extends NavigationStateRenderer {
     static final String NOT_SUPPORT_REROUTE = "BeforeEvent.rerouteTo() with a client side route is not supported";
 
     private String clientForwardRoute;
+    private boolean serverForwarded = false;
 
     private ContinueNavigationAction continueNavigationAction;
 
@@ -69,6 +70,15 @@ public String getClientForwardRoute() {
         return clientForwardRoute;
     }
 
+    /**
+     * Gets the server forwarded flag.
+     *
+     * @return the server forwarded flag.
+     */
+    public boolean isServerForwarded() {
+        return serverForwarded;
+    }
+
     @Override
     public int handle(NavigationEvent event) {
 
@@ -90,6 +100,9 @@ protected Optional<Integer> handleTriggeredBeforeEvent(
                 clientForwardRoute = beforeEvent.getUnknownForward();
                 return Optional.of(HttpStatusCode.OK.getCode());
             }
+        } else if (beforeEvent.hasForwardTarget()) {
+            // Forwarded to another route, e.g. a login view
+            serverForwarded = true;
         }
 
         if (beforeEvent.hasUnknownReroute()) {

flow-server/src/main/java/com/vaadin/flow/component/page/History.java

@@ -186,9 +186,10 @@ public void pushState(JsonValue state, Location location) {
                 location);
         // Second parameter is title which is currently ignored according to
         // https://developer.mozilla.org/en-US/docs/Web/API/History_API
-        ui.getPage().executeJs(
-                "setTimeout(() => { window.history.pushState($0, '', $1); window.dispatchEvent(new PopStateEvent('popstate', {state: 'vaadin-router-ignore'})); })",
-                state, pathWithQueryParameters);
+        final String pushStateScript = ui.getSession().getConfiguration()
+                .isReactEnabled() ? "window.history.pushState($0, '', $1);"
+                        : "setTimeout(() => { window.history.pushState($0, '', $1); window.dispatchEvent(new PopStateEvent('popstate', {state: 'vaadin-router-ignore'})); })";
+        ui.getPage().executeJs(pushStateScript, state, pathWithQueryParameters);
     }
 
     /**
@@ -225,9 +226,11 @@ public void replaceState(JsonValue state, Location location) {
                 location);
         // Second parameter is title which is currently ignored according to
         // https://developer.mozilla.org/en-US/docs/Web/API/History_API
-        ui.getPage().executeJs(
-                "setTimeout(() => { window.history.replaceState($0, '', $1); window.dispatchEvent(new PopStateEvent('popstate', {state: 'vaadin-router-ignore'})); })",
-                state, pathWithQueryParameters);
+        final String replaceStateScript = ui.getSession().getConfiguration()
+                .isReactEnabled() ? "window.history.replaceState($0, '', $1);"
+                        : "setTimeout(() => { window.history.replaceState($0, '', $1); window.dispatchEvent(new PopStateEvent('popstate', {state: 'vaadin-router-ignore'})); })";
+        ui.getPage().executeJs(replaceStateScript, state,
+                pathWithQueryParameters);
     }
 
     /**

flow-server/src/main/java/com/vaadin/flow/router/BeforeLeaveEvent.java

@@ -94,7 +94,12 @@ public void proceed() {
                             event.getLocation(), event.getUI(),
                             NavigationTrigger.PROGRAMMATIC);
                 }
+
+                final UI ui = event.getUI();
                 handler.handle(event);
+                if (ui.getSession().getConfiguration().isReactEnabled()) {
+                    ui.getInternals().clearLastHandledNavigation();
+                }
                 setReferences(null, null);
             }
         }

flow-server/src/main/java/com/vaadin/flow/router/internal/AbstractNavigationStateRenderer.java

@@ -282,14 +282,21 @@ private void pushHistoryStateIfNeeded(NavigationEvent event, UI ui) {
                                         .getPathWithQueryParameters()))) {
 
             if (shouldPushHistoryState(event)) {
-                pushHistoryState(event);
+                if (ui.getSession().getConfiguration().isReactEnabled()) {
+                    ui.getPage().executeJs(
+                            "setTimeout(() => { window.dispatchEvent(new CustomEvent('vaadin-navigate', { detail: { url: $0 } })); })",
+                            event.getLocation().getPathWithQueryParameters());
+                } else {
+                    pushHistoryState(event);
+                }
             }
 
             ui.getInternals().setLastHandledNavigation(event.getLocation());
-        } else if (ui.getInternals().getSession().getConfiguration()
-                .isReactEnabled()) {
+        } else if (ui.getSession().getConfiguration().isReactEnabled()) {
             if (shouldPushHistoryState(event)) {
-                pushHistoryState(event);
+                ui.getPage().executeJs(
+                        "setTimeout(() => { window.dispatchEvent(new CustomEvent('vaadin-navigate', { detail: { url: $0 } })); })",
+                        event.getLocation().getPathWithQueryParameters());
             }
         }
     }