From d1415162cb799b6a735c84c82429b211334b91fd Mon Sep 17 00:00:00 2001
From: Andrew Scott <atscott@google.com>
Date: Wed, 9 Sep 2020 10:49:35 -0700
Subject: [PATCH] fix(core): clear the `RefreshTransplantedView` when detached
 (#38768)

The `RefreshTransplantedView` flag is used to indicate that the view or one of its children
is transplanted and dirty, so it should still be refreshed as part of change detection.
This flag is set on the transplanted view itself as well setting a
counter on as its parents.
When a transplanted view is detached and still has this flag, it means
it got detached before it was refreshed. This can happen for "backwards
references" or transplanted views that are inserted at a location that
was already checked. In this case, we should decrement the parent
counters _and_ clear the flag on the detached view so it's not seen as
"transplanted" anymore (it is detached and has no parent counters to
adjust).

fixes #38619

PR Close #38768
---
 .../core/src/render3/node_manipulation.ts     |  1 +
 ...change_detection_transplanted_view_spec.ts | 36 ++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/packages/core/src/render3/node_manipulation.ts b/packages/core/src/render3/node_manipulation.ts
index 1e0dba6d78..8903073181 100644
--- a/packages/core/src/render3/node_manipulation.ts
+++ b/packages/core/src/render3/node_manipulation.ts
@@ -300,6 +300,7 @@ function detachMovedView(declarationContainer: LContainer, lView: LView) {
   // would be cleared and the counter decremented), we need to decrement the view counter here
   // instead.
   if (lView[FLAGS] & LViewFlags.RefreshTransplantedView) {
+    lView[FLAGS] &= ~LViewFlags.RefreshTransplantedView;
     updateTransplantedViewCount(insertionLContainer, -1);
   }
 
diff --git a/packages/core/test/acceptance/change_detection_transplanted_view_spec.ts b/packages/core/test/acceptance/change_detection_transplanted_view_spec.ts
index d3c8f99f4b..815aebcb5c 100644
--- a/packages/core/test/acceptance/change_detection_transplanted_view_spec.ts
+++ b/packages/core/test/acceptance/change_detection_transplanted_view_spec.ts
@@ -7,7 +7,7 @@
  */
 
 import {CommonModule} from '@angular/common';
-import {ChangeDetectionStrategy, ChangeDetectorRef, Component, DoCheck, Input, TemplateRef, Type, ViewChild} from '@angular/core';
+import {ChangeDetectionStrategy, ChangeDetectorRef, Component, DoCheck, Input, TemplateRef, Type, ViewChild, ViewContainerRef} from '@angular/core';
 import {AfterViewChecked} from '@angular/core/src/core';
 import {ComponentFixture, TestBed} from '@angular/core/testing';
 import {expect} from '@angular/platform-browser/testing/src/matchers';
@@ -594,6 +594,40 @@ describe('change detection for transplanted views', () => {
             'SheldonSheldonSheldon',
             'Expected transplanted view to be refreshed even when insertion is not dirty');
   });
+
+  it('should not fail when change detecting detached transplanted view', () => {
+    @Component({template: '<ng-template>{{incrementChecks()}}</ng-template>'})
+    class AppComponent {
+      @ViewChild(TemplateRef) templateRef!: TemplateRef<{}>;
+
+      constructor(readonly rootVref: ViewContainerRef, readonly cdr: ChangeDetectorRef) {}
+
+      checks = 0;
+      incrementChecks() {
+        this.checks++;
+      }
+    }
+
+    const fixture = TestBed.configureTestingModule({declarations: [AppComponent]})
+                        .createComponent(AppComponent);
+    const component = fixture.componentInstance;
+    fixture.detectChanges();
+
+    const viewRef = component.templateRef.createEmbeddedView({});
+    // This `ViewContainerRef` is for the root view
+    component.rootVref.insert(viewRef);
+    // `detectChanges` on this `ChangeDetectorRef` will refresh this view and children, not the root
+    // view that has the transplanted `viewRef` inserted.
+    component.cdr.detectChanges();
+    // The template should not have been refreshed because it was inserted "above" the component so
+    // `detectChanges` will not refresh it.
+    expect(component.checks).toEqual(0);
+
+    // Detach view, manually call `detectChanges`, and verify the template was refreshed
+    component.rootVref.detach();
+    viewRef.detectChanges();
+    expect(component.checks).toEqual(1);
+  });
 });
 
 function trim(text: string|null): string {