fix: render markdown content on re-attachment (#7808)

Copilot · sissbruecker · web-flow · commit b3c77e0809b7 · 2025-08-07T07:57:56.000+02:00
* Initial plan

* Fix re-attaching Markdown component content disappearing issue

Co-authored-by: sissbruecker &lt;357820+sissbruecker@users.noreply.github.com&gt;

* run formatter

---------

Co-authored-by: copilot-swe-agent[bot] &lt;198982749+Copilot@users.noreply.github.com&gt;
Co-authored-by: sissbruecker &lt;357820+sissbruecker@users.noreply.github.com&gt;
Co-authored-by: Sascha Ißbrücker &lt;sissbruecker@vaadin.com&gt;
diff --git a/vaadin-markdown-flow-parent/vaadin-markdown-flow/src/main/java/com/vaadin/flow/component/markdown/Markdown.java b/vaadin-markdown-flow-parent/vaadin-markdown-flow/src/main/java/com/vaadin/flow/component/markdown/Markdown.java
@@ -17,6 +17,7 @@
 
 import java.util.Objects;
 
+import com.vaadin.flow.component.AttachEvent;
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.HasSize;
 import com.vaadin.flow.component.Tag;
@@ -87,6 +88,15 @@ public String getContent() {
         return serverContent;
     }
 
+    @Override
+    protected void onAttach(AttachEvent attachEvent) {
+        super.onAttach(attachEvent);
+        if (serverContent != null) {
+            clientContent = null;
+            scheduleContentUpdate();
+        }
+    }
+
     private void scheduleContentUpdate() {
         getElement().getNode()
                 .runWhenAttached(ui -> ui.beforeClientResponse(this, ctx -> {
diff --git a/vaadin-markdown-flow-parent/vaadin-markdown-flow/src/test/java/com/vaadin/flow/component/markdown/tests/MarkdownTest.java b/vaadin-markdown-flow-parent/vaadin-markdown-flow/src/test/java/com/vaadin/flow/component/markdown/tests/MarkdownTest.java
@@ -138,6 +138,21 @@ public void testDetach_setContent_attach() {
         Assert.assertEquals("**Hello** _World_", markdown.getContent());
     }
 
+    @Test
+    public void testReAttachment_contentPreserved() {
+        // Set content while attached
+        markdown.setContent("**Hello** _World_");
+        assertUpdateMarkdownCall(markdown, "**Hello** _World_", false);
+
+        // Detach the component
+        markdown.removeFromParent();
+
+        // Re-attach the component - content should be sent to client again
+        ui.add(markdown);
+        assertUpdateMarkdownCall(markdown, "**Hello** _World_", false);
+        Assert.assertEquals("**Hello** _World_", markdown.getContent());
+    }
+
     private void assertUpdateMarkdownCall(Component component, String content,
             boolean isAppend) {
         var pendingJavaScriptInvocations = getPendingJavaScriptInvocations();
