fix: force page reload only for redefined classes (#21274)

* fix: force page reload only for redefined classes

When Hotswapper force page reload is active, trigger page reload
only for redefined classes, not when they are loaded for the
first time.

Fixes #21273

* fix test name

Author: mcollovati

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

@@ -277,7 +277,8 @@ private void onHotswapInternal(HashSet<Class<?>> classes,
             }
         }
         forceBrowserReload = forceBrowserReload
-                || getForceReloadHolder(vaadinService).shouldReloadPage();
+                || (getForceReloadHolder(vaadinService).shouldReloadPage()
+                        && redefined);
 
         boolean uiTreeNeedsRefresh = false;
         EnumMap<UIRefreshStrategy, List<UI>> refreshActions = null;

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

@@ -944,7 +944,7 @@ public void onHotswap_mixedPushState_classInUITreeChanged_liveReloadTriggered()
     }
 
     @Test
-    public void onHotswap_pushDisabled_forcePageReload_fullReloadTriggered()
+    public void onHotswap_pushDisabled_forcePageReload_redefinedClass_fullReloadTriggered()
             throws ServiceException {
         VaadinSession session = createMockVaadinSession();
         hotswapper.sessionInit(new SessionInitEvent(service, session, null));
@@ -959,6 +959,22 @@ public void onHotswap_pushDisabled_forcePageReload_fullReloadTriggered()
         Mockito.verify(liveReload).reload();
     }
 
+    @Test
+    public void onHotswap_pushDisabled_forcePageReload_loadedClass_notReload()
+            throws ServiceException {
+        VaadinSession session = createMockVaadinSession();
+        hotswapper.sessionInit(new SessionInitEvent(service, session, null));
+
+        RefreshTestingUI ui = initUIAndNavigateTo(session, MyRoute.class);
+
+        Hotswapper.forcePageReload(service, true);
+        hotswapper.onHotswap(new String[] { MyRoute.class.getName() }, false);
+
+        ui.assertNotRefreshed();
+        Mockito.verify(liveReload, never()).refresh(anyBoolean());
+        Mockito.verify(liveReload, never()).reload();
+    }
+
     @Test
     public void onHotswap_pushDisabled_forcePageReloadWithSystemProperty_fullReloadTriggered()
             throws ServiceException {
@@ -986,7 +1002,7 @@ public void onHotswap_pushDisabled_forcePageReloadWithSystemProperty_fullReloadT
     }
 
     @Test
-    public void onHotswap_pushEnabled_forcePageReload_fullReloadTriggered()
+    public void onHotswap_pushEnabled_forcePageReload_redefinedClass_fullReloadTriggered()
             throws ServiceException {
         VaadinSession session = createMockVaadinSession();
         hotswapper.sessionInit(new SessionInitEvent(service, session, null));
@@ -1002,6 +1018,23 @@ public void onHotswap_pushEnabled_forcePageReload_fullReloadTriggered()
         Mockito.verify(liveReload).reload();
     }
 
+    @Test
+    public void onHotswap_pushEnabled_forcePageReload_loadedClass_noReload()
+            throws ServiceException {
+        VaadinSession session = createMockVaadinSession();
+        hotswapper.sessionInit(new SessionInitEvent(service, session, null));
+
+        RefreshTestingUI ui = initUIAndNavigateTo(session, MyRoute.class);
+        ui.enablePush();
+
+        Hotswapper.forcePageReload(service, true);
+        hotswapper.onHotswap(new String[] { MyRoute.class.getName() }, false);
+
+        ui.assertNotRefreshed();
+        Mockito.verify(liveReload, never()).refresh(anyBoolean());
+        Mockito.verify(liveReload, never()).reload();
+    }
+
     @Test
     public void onHotswap_pushEnabled_forcePageReloadWithSystemProperty_fullReloadTriggered()
             throws ServiceException {