From d4449fce21bebbb18f9e1341f1675cdbec7e83ac Mon Sep 17 00:00:00 2001
From: Andrew Kushnir <akushnir@google.com>
Date: Tue, 13 Aug 2024 18:07:52 -0700
Subject: [PATCH] fix(core): handle hydration of components that project
 content conditionally (#57383)

This commit fixes an issue when hydration serialization tries to calculate DOM path to a content projection node (`<ng-content>`), but such nodes do not have DOM representation.

Resolves #56750.

PR Close #57383
---
 packages/core/src/hydration/annotate.ts       |  6 ++
 .../platform-server/test/hydration_spec.ts    | 66 +++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/packages/core/src/hydration/annotate.ts b/packages/core/src/hydration/annotate.ts
index 75258ca04d2..1f9566effe4 100644
--- a/packages/core/src/hydration/annotate.ts
+++ b/packages/core/src/hydration/annotate.ts
@@ -583,6 +583,12 @@ function conditionallyAnnotateNodePath(
   lView: LView<unknown>,
   excludedParentNodes: Set<number> | null,
 ) {
+  if (isProjectionTNode(tNode)) {
+    // Do not annotate projection nodes (<ng-content />), since
+    // they don't have a corresponding DOM node representing them.
+    return;
+  }
+
   // Handle case #1 described above.
   if (
     tNode.projectionNext &&
diff --git a/packages/platform-server/test/hydration_spec.ts b/packages/platform-server/test/hydration_spec.ts
index 872aacf3e4e..ac25d07ff43 100644
--- a/packages/platform-server/test/hydration_spec.ts
+++ b/packages/platform-server/test/hydration_spec.ts
@@ -5685,6 +5685,72 @@ describe('platform-server hydration integration', () => {
           verifyClientAndSSRContentsMatch(ssrContents, clientRootNode);
         });
 
+        it('should support cases when some element nodes are not projected', async () => {
+          @Component({
+            standalone: true,
+            selector: 'app-dropdown-content',
+            template: `<ng-content />`,
+          })
+          class DropdownContentComponent {}
+
+          @Component({
+            standalone: true,
+            selector: 'app-dropdown',
+            template: `
+              @if (false) {
+                <ng-content select="app-dropdown-content" />
+              }
+            `,
+          })
+          class DropdownComponent {}
+
+          @Component({
+            standalone: true,
+            imports: [DropdownComponent, DropdownContentComponent],
+            selector: 'app-menu',
+            template: `
+              <app-dropdown>
+                <app-dropdown-content>
+                  <ng-content />
+                </app-dropdown-content>
+              </app-dropdown>
+            `,
+          })
+          class MenuComponent {}
+
+          @Component({
+            selector: 'app',
+            standalone: true,
+            imports: [MenuComponent],
+            template: `
+              <app-menu>
+                Menu Content
+              </app-menu>
+            `,
+          })
+          class SimpleComponent {}
+
+          const html = await ssr(SimpleComponent);
+          const ssrContents = getAppContents(html);
+
+          expect(ssrContents).toContain('<app ngh');
+
+          resetTViewsFor(
+            SimpleComponent,
+            MenuComponent,
+            DropdownComponent,
+            DropdownContentComponent,
+          );
+
+          const appRef = await renderAndHydrate(doc, html, SimpleComponent);
+          const compRef = getComponentRef<SimpleComponent>(appRef);
+          appRef.tick();
+
+          const clientRootNode = compRef.location.nativeElement;
+          verifyAllNodesClaimedForHydration(clientRootNode);
+          verifyClientAndSSRContentsMatch(ssrContents, clientRootNode);
+        });
+
         it('should support cases when view containers are not projected', async () => {
           @Component({
             standalone: true,