From 6115df380df3b5ba76bfed50801ee817616bdbc3 Mon Sep 17 00:00:00 2001
From: Vaadin Bot <vaadin-bot@users.noreply.github.com>
Date: Mon, 20 Jan 2025 16:32:37 +0100
Subject: [PATCH] fix: trigger refresh from client on hotswap with PUSH
 (#20848) (#20886)

* fix: trigger refresh from client on hotswap with PUSH

When PUSH is enabled, Flow Hotswapper uses it to refresh only the affected UIs.
However, this can cause issues if Flow views contain code that relies on
VaadinRequest thread local, since hotswap refresh start in a background thread.
This change defines a client side event listener to trigger the refresh,
and uses PUSH only to fires the event.

Fixes #20843

* fix test

Co-authored-by: Marco Collovati <marco@vaadin.com>
---
 .../com/vaadin/flow/hotswap/Hotswapper.java   | 22 ++++++++++++---
 .../vaadin/flow/hotswap/HotswapperTest.java   | 27 ++++++++++++++-----
 2 files changed, 38 insertions(+), 11 deletions(-)

diff --git a/flow-server/src/main/java/com/vaadin/flow/hotswap/Hotswapper.java b/flow-server/src/main/java/com/vaadin/flow/hotswap/Hotswapper.java
index cc40fb440ca..c6de55b8b17 100644
--- a/flow-server/src/main/java/com/vaadin/flow/hotswap/Hotswapper.java
+++ b/flow-server/src/main/java/com/vaadin/flow/hotswap/Hotswapper.java
@@ -472,9 +472,11 @@ private void triggerClientUpdate(
             LOGGER.debug(
                     "Triggering re-navigation to current route for UIs affected by classes changes.");
             for (UIRefreshStrategy action : uisToRefresh.keySet()) {
-                uisToRefresh.get(action)
-                        .forEach(ui -> ui.access(() -> ui.refreshCurrentRoute(
-                                action == UIRefreshStrategy.PUSH_REFRESH_CHAIN)));
+                String triggerEventJS = String.format(
+                        "window.dispatchEvent(new CustomEvent(\"vaadin-refresh-ui\", { detail: { fullRefresh: %s }}));",
+                        action == UIRefreshStrategy.PUSH_REFRESH_CHAIN);
+                uisToRefresh.get(action).forEach(ui -> ui
+                        .access(() -> ui.getPage().executeJs(triggerEventJS)));
             }
         }
     }
@@ -507,7 +509,19 @@ public void serviceDestroy(ServiceDestroyEvent event) {
 
     @Override
     public void uiInit(UIInitEvent event) {
-        sessions.add(event.getUI().getSession());
+        UI ui = event.getUI();
+        sessions.add(ui.getSession());
+        ui.getPage().executeJs(
+                """
+                        const $wnd = window;
+                        window.addEventListener('vaadin-ui-refresh', (ev) => {
+                            const senderFn = $wnd.Vaadin?.Flow?.clients[$0]?.sendEventMessage;
+                            if (senderFn) {
+                                senderFn(1, "ui-refresh", ev.detail);
+                            }
+                        });
+                        """,
+                ui.getInternals().getAppId());
     }
 
     /**
diff --git a/flow-server/src/test/java/com/vaadin/flow/hotswap/HotswapperTest.java b/flow-server/src/test/java/com/vaadin/flow/hotswap/HotswapperTest.java
index 70181a1de2e..ab1bc7f6297 100644
--- a/flow-server/src/test/java/com/vaadin/flow/hotswap/HotswapperTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/hotswap/HotswapperTest.java
@@ -24,6 +24,8 @@
 import java.util.UUID;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Supplier;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import org.junit.Assert;
 import org.junit.Before;
@@ -35,6 +37,7 @@
 import com.vaadin.flow.component.HasComponents;
 import com.vaadin.flow.component.HasElement;
 import com.vaadin.flow.component.Tag;
+import com.vaadin.flow.component.page.Page;
 import com.vaadin.flow.di.Lookup;
 import com.vaadin.flow.internal.BrowserLiveReload;
 import com.vaadin.flow.internal.BrowserLiveReloadAccessor;
@@ -1153,20 +1156,30 @@ private RefreshTestingUI initUIAndNavigateTo(VaadinSession session,
 
     private static class RefreshTestingUI extends MockUI {
 
+        private static final Pattern UI_REFRESH_EVENT = Pattern.compile(
+                ".*new CustomEvent\\(\"vaadin-refresh-ui\",\\s*\\{\\s*detail:\\s*\\{\\s*fullRefresh:\\s*(true|false)\\s*}\\s*}\\).*");
         private Boolean refreshRouteChainRequested;
 
+        private final Page pageSpy;
+
         public RefreshTestingUI(VaadinSession session) {
             super(session);
+            pageSpy = Mockito.spy(super.getPage());
+            // Intercept javascript executions to check if the custom ui refresh
+            // event dispatch has been registered.
+            Mockito.doAnswer(i -> {
+                Matcher matcher = UI_REFRESH_EVENT.matcher(i.getArgument(0));
+                if (matcher.matches()) {
+                    refreshRouteChainRequested = Boolean
+                            .parseBoolean(matcher.group(1));
+                }
+                return null;
+            }).when(pageSpy).executeJs(Mockito.anyString());
         }
 
         @Override
-        public void refreshCurrentRoute(boolean refreshRouteChain) {
-            refreshRouteChainRequested = refreshRouteChain;
-            // No need to perform real navigation, tests only need to know if
-            // the method has been invoked.
-            // Navigation would fail anyway because of usage of method scoped
-            // classes. Blocking navigation prevents logs to be bloated by
-            // exception stack traces.
+        public Page getPage() {
+            return pageSpy;
         }
 
         void assertNotRefreshed() {