fix: reload route configuration upon layout changes

When a [At]Layout annotated class is modified, the changes are not
propagated to the route registry after hotswap happens.
This change updates Route registry layouts configuration and re-registers
routes potentially impacted by the change to apply the new settings.
It also checks the route target chain for active UIs in order to
trigger a page refresh if the layout changes should be applied.

Fixes #20111

flow-server/src/main/java/com/vaadin/flow/hotswap/Hotswapper.java

@@ -39,6 +39,8 @@
 import com.vaadin.flow.di.Lookup;
 import com.vaadin.flow.internal.BrowserLiveReload;
 import com.vaadin.flow.internal.BrowserLiveReloadAccessor;
+import com.vaadin.flow.router.internal.RouteTarget;
+import com.vaadin.flow.server.RouteRegistry;
 import com.vaadin.flow.server.ServiceDestroyEvent;
 import com.vaadin.flow.server.ServiceDestroyListener;
 import com.vaadin.flow.server.ServiceException;
@@ -309,6 +311,19 @@ private UIRefreshStrategy computeRefreshStrategy(UI ui,
             refreshStrategy = computeRefreshStrategyForUITree(ui,
                     changedClasses, targetsChain, route);
         }
+        // A different layout might have been applied after hotswap
+        if (refreshStrategy == UIRefreshStrategy.SKIP) {
+            RouteRegistry registry = ui.getInternals().getRouter()
+                    .getRegistry();
+            RouteTarget routeTarget = registry
+                    .getNavigationRouteTarget(
+                            ui.getActiveViewLocation().getPath())
+                    .getRouteTarget();
+            if (routeTarget != null && routeTarget.getParentLayouts().stream()
+                    .anyMatch(changedClasses::contains)) {
+                refreshStrategy = UIRefreshStrategy.PUSH_REFRESH_CHAIN;
+            }
+        }
 
         // If push is not enabled we can only request a full page refresh
         if (refreshStrategy != UIRefreshStrategy.SKIP && !pushEnabled) {

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

@@ -35,6 +35,7 @@
 import com.vaadin.flow.internal.ReflectTools;
 import com.vaadin.flow.router.BeforeEnterListener;
 import com.vaadin.flow.router.HasErrorParameter;
+import com.vaadin.flow.router.Layout;
 import com.vaadin.flow.router.Menu;
 import com.vaadin.flow.router.MenuData;
 import com.vaadin.flow.router.NotFoundException;
@@ -55,7 +56,6 @@
 import com.vaadin.flow.server.auth.NavigationAccessControl;
 import com.vaadin.flow.server.auth.NavigationContext;
 import com.vaadin.flow.server.auth.ViewAccessChecker;
-import com.vaadin.flow.router.Layout;
 import com.vaadin.flow.server.menu.MenuRegistry;
 import com.vaadin.flow.shared.Registration;
 
@@ -610,6 +610,19 @@ public void setLayout(Class<? extends RouterLayout> layout) {
         }
     }
 
+    void updateLayout(Class<? extends RouterLayout> layout) {
+        if (layout == null) {
+            return;
+        }
+        synchronized (layouts) {
+            layouts.entrySet()
+                    .removeIf(entry -> layout.equals(entry.getValue()));
+            if (layout.isAnnotationPresent(Layout.class)) {
+                layouts.put(layout.getAnnotation(Layout.class).value(), layout);
+            }
+        }
+    }
+
     @Override
     public Class<? extends RouterLayout> getLayout(String path) {
         Optional<String> first = layouts.keySet().stream()

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

@@ -41,6 +41,7 @@
 import com.vaadin.flow.router.ParentLayout;
 import com.vaadin.flow.router.Route;
 import com.vaadin.flow.router.RouteAlias;
+import com.vaadin.flow.router.RouteBaseData;
 import com.vaadin.flow.router.RouteConfiguration;
 import com.vaadin.flow.router.RoutePathProvider;
 import com.vaadin.flow.router.RoutePrefix;
@@ -125,7 +126,7 @@ public static List<Class<? extends RouterLayout>> getParentLayouts(
 
         if (hasRouteAndPathMatches && !route.get().layout().equals(UI.class)) {
             list.addAll(collectRouteParentLayouts(route.get().layout()));
-        } else if (route.get().autoLayout() && hasRouteAndPathMatches
+        } else if (hasRouteAndPathMatches && route.get().autoLayout()
                 && route.get().layout().equals(UI.class)
                 && handledRegistry.hasLayout(path)) {
             list.addAll(
@@ -435,18 +436,39 @@ public static void updateRouteRegistry(RouteRegistry registry,
         modifiedClasses.stream()
                 .filter(clazz -> !Component.class.isAssignableFrom(clazz))
                 .forEach(nonFlowComponentsToRemove::add);
+        Set<Class<? extends RouterLayout>> layouts = new HashSet<>();
 
         boolean isSessionRegistry = registry instanceof SessionRouteRegistry;
         Predicate<Class<? extends Component>> modifiedClassesRouteRemovalFilter = clazz -> !isSessionRegistry;
 
         if (registry instanceof AbstractRouteRegistry abstractRouteRegistry) {
+
+            // update layouts
+            filterLayoutClasses(deletedClasses).forEach(layouts::add);
+            filterLayoutClasses(modifiedClasses).forEach(layouts::add);
+            filterLayoutClasses(addedClasses).forEach(layouts::add);
+            layouts.forEach(abstractRouteRegistry::updateLayout);
+            if (!layouts.isEmpty()) {
+                // Gather routes that don't have a layout or reference a layout
+                // that has been changed.
+                // Mark these routes as modified so they can be re-registered
+                // with the correct layouts applied.
+                registry.getRegisteredRoutes().stream()
+                        .filter(rd -> rd.getParentLayouts().isEmpty()
+                                || rd.getParentLayouts().stream()
+                                        .anyMatch(layouts::contains))
+                        .map(RouteBaseData::getNavigationTarget)
+                        .forEach(modifiedClasses::add);
+            }
+
             Map<String, RouteTarget> routesMap = abstractRouteRegistry
                     .getConfiguration().getRoutesMap();
             Map<? extends Class<? extends Component>, RouteTarget> routeTargets = registry
                     .getRegisteredRoutes().stream()
                     .map(routeData -> routesMap.get(routeData.getTemplate()))
                     .filter(Objects::nonNull).collect(Collectors.toMap(
                             RouteTarget::getTarget, Function.identity()));
+
             modifiedClassesRouteRemovalFilter = modifiedClassesRouteRemovalFilter
                     .and(clazz -> {
                         RouteTarget routeTarget = routeTargets.get(clazz);
@@ -522,6 +544,14 @@ public static void updateRouteRegistry(RouteRegistry registry,
         });
     }
 
+    @SuppressWarnings("unchecked")
+    private static Stream<Class<? extends RouterLayout>> filterLayoutClasses(
+            Set<Class<?>> classes) {
+        return filterComponentClasses(classes)
+                .filter(RouterLayout.class::isAssignableFrom)
+                .map(clazz -> (Class<? extends RouterLayout>) clazz);
+    }
+
     @SuppressWarnings("unchecked")
     private static Stream<Class<? extends Component>> filterComponentClasses(
             Set<Class<?>> classes) {

flow-server/src/test/java/com/vaadin/flow/hotswap/HotswapperTest.java

@@ -38,9 +38,11 @@
 import com.vaadin.flow.di.Lookup;
 import com.vaadin.flow.internal.BrowserLiveReload;
 import com.vaadin.flow.internal.BrowserLiveReloadAccessor;
+import com.vaadin.flow.router.RouteConfiguration;
 import com.vaadin.flow.router.RouterLayout;
 import com.vaadin.flow.server.MockVaadinServletService;
 import com.vaadin.flow.server.MockVaadinSession;
+import com.vaadin.flow.server.RouteRegistry;
 import com.vaadin.flow.server.ServiceDestroyEvent;
 import com.vaadin.flow.server.ServiceDestroyListener;
 import com.vaadin.flow.server.ServiceException;
@@ -281,6 +283,32 @@ public void onHotswap_pushDisabled_routeLayoutClassChanged_UINotRefreshedButLive
         Mockito.verify(liveReload).refresh(anyBoolean());
     }
 
+    @Test
+    public void onHotswap_pushDisabled_routeTargetChainChanged_UINotRefreshedButLiveReloadTriggered()
+            throws ServiceException {
+        VaadinSession session = createMockVaadinSession();
+        hotswapper.sessionInit(new SessionInitEvent(service, session, null));
+
+        class NewLayout extends Component implements RouterLayout {
+        }
+        RefreshTestingUI ui = initUIAndNavigateTo(session, MyRoute.class,
+                MyLayout.class);
+        RouteRegistry registry = ui.getInternals().getRouter().getRegistry();
+        RouteConfiguration routeConfiguration = RouteConfiguration
+                .forRegistry(registry);
+        routeConfiguration.update(() -> {
+            String path = ui.getActiveViewLocation().getPath();
+            routeConfiguration.removeRoute(path);
+            routeConfiguration.setRoute(path, MyRoute.class,
+                    List.of(NewLayout.class));
+        });
+
+        hotswapper.onHotswap(new String[] { NewLayout.class.getName() }, true);
+
+        ui.assertNotRefreshed();
+        Mockito.verify(liveReload).refresh(anyBoolean());
+    }
+
     @Test
     public void onHotswap_pushDisabled_routeChildClassChanged_UINotRefreshedButLiveReloadTriggered()
             throws ServiceException {
@@ -389,6 +417,34 @@ public void onHotswap_pushEnabled_routeLayoutClassChanged_activeChainRefreshed()
         Mockito.verify(liveReload, never()).refresh(anyBoolean());
     }
 
+    @Test
+    public void onHotswap_pushEnabled_routeTargetChainChanged_activeChainRefreshed()
+            throws ServiceException {
+        VaadinSession session = createMockVaadinSession();
+        hotswapper.sessionInit(new SessionInitEvent(service, session, null));
+
+        class NewLayout extends Component implements RouterLayout {
+        }
+        RefreshTestingUI ui = initUIAndNavigateTo(session, MyRoute.class,
+                MyLayout.class);
+        ui.enablePush();
+        RouteRegistry registry = ui.getInternals().getRouter().getRegistry();
+        RouteConfiguration routeConfiguration = RouteConfiguration
+                .forRegistry(registry);
+        routeConfiguration.update(() -> {
+            String path = ui.getActiveViewLocation().getPath();
+            routeConfiguration.removeRoute(path);
+            routeConfiguration.setRoute(path, MyRoute.class,
+                    List.of(NewLayout.class));
+        });
+
+        hotswapper.onHotswap(new String[] { NewLayout.class.getName() }, true);
+
+        ui.assertChainRefreshed();
+        Mockito.verify(liveReload, never()).reload();
+        Mockito.verify(liveReload, never()).refresh(anyBoolean());
+    }
+
     @Test
     public void onHotswap_pushEnabled_routeChildrenClassChanged_routeRefreshed()
             throws ServiceException {