fix(animations): retain state styling for nodes that are moved around (#23686)

PR Close #23686

packages/animations/browser/src/render/transition_animation_engine.ts

@@ -28,13 +28,15 @@ const STAR_SELECTOR = '.ng-star-inserted';
 const EMPTY_PLAYER_ARRAY: TransitionAnimationPlayer[] = [];
 const NULL_REMOVAL_STATE: ElementAnimationState = {
   namespaceId: '',
-  setForRemoval: null,
+  setForRemoval: false,
+  setForMove: false,
   hasAnimation: false,
   removedBeforeQueried: false
 };
 const NULL_REMOVED_QUERIED_STATE: ElementAnimationState = {
   namespaceId: '',
-  setForRemoval: null,
+  setForMove: false,
+  setForRemoval: false,
   hasAnimation: false,
   removedBeforeQueried: true
 };
@@ -58,7 +60,8 @@ export interface QueueInstruction {
 export const REMOVAL_FLAG = '__ng_removed';
 
 export interface ElementAnimationState {
-  setForRemoval: any;
+  setForRemoval: boolean;
+  setForMove: boolean;
   hasAnimation: boolean;
   namespaceId: string;
   removedBeforeQueried: boolean;
@@ -660,6 +663,11 @@ export class TransitionAnimationEngine {
     const details = element[REMOVAL_FLAG] as ElementAnimationState;
     if (details && details.setForRemoval) {
       details.setForRemoval = false;
+      details.setForMove = true;
+      const index = this.collectedLeaveElements.indexOf(element);
+      if (index >= 0) {
+        this.collectedLeaveElements.splice(index, 1);
+      }
     }
 
     // in the event that the namespaceId is blank then the caller
@@ -946,9 +954,18 @@ export class TransitionAnimationEngine {
       const ns = this._namespaceList[i];
       ns.drainQueuedTransitions(microtaskId).forEach(entry => {
         const player = entry.player;
+        const element = entry.element;
         allPlayers.push(player);
 
-        const element = entry.element;
+        if (this.collectedEnterElements.length) {
+          const details = element[REMOVAL_FLAG] as ElementAnimationState;
+          // move animations are currently not supported...
+          if (details && details.setForMove) {
+            player.destroy();
+            return;
+          }
+        }
+
         if (!bodyNode || !this.driver.containsElement(bodyNode, element)) {
           player.destroy();
           return;

packages/core/test/animation/animation_integration_spec.ts

@@ -1453,6 +1453,117 @@ const DEFAULT_COMPONENT_ID = '1';
             .toBeTruthy();
       });
 
+      it('should retain state styles when the underlying DOM structure changes even if there are no insert/remove animations',
+         () => {
+           @Component({
+             selector: 'ani-cmp',
+             template: `
+            <div class="item" *ngFor="let item of items" [@color]="colorExp">
+              {{ item }}
+            </div>
+          `,
+             animations: [trigger('color', [state('green', style({backgroundColor: 'green'}))])]
+           })
+           class Cmp {
+             public colorExp = 'green';
+             public items = [0, 1, 2, 3];
+
+             reorder() {
+               const temp = this.items[0];
+               this.items[0] = this.items[1];
+               this.items[1] = temp;
+             }
+           }
+
+           TestBed.configureTestingModule({declarations: [Cmp]});
+
+           const fixture = TestBed.createComponent(Cmp);
+           const cmp = fixture.componentInstance;
+           fixture.detectChanges();
+
+           let elements: HTMLElement[] = fixture.nativeElement.querySelectorAll('.item');
+           assertBackgroundColor(elements[0], 'green');
+           assertBackgroundColor(elements[1], 'green');
+           assertBackgroundColor(elements[2], 'green');
+           assertBackgroundColor(elements[3], 'green');
+
+           elements[0].title = '0a';
+           elements[1].title = '1a';
+
+           cmp.reorder();
+           fixture.detectChanges();
+
+           elements = fixture.nativeElement.querySelectorAll('.item');
+           assertBackgroundColor(elements[0], 'green');
+           assertBackgroundColor(elements[1], 'green');
+           assertBackgroundColor(elements[2], 'green');
+           assertBackgroundColor(elements[3], 'green');
+
+           function assertBackgroundColor(element: HTMLElement, color: string) {
+             expect(element.style.getPropertyValue('background-color')).toEqual(color);
+           }
+         });
+
+      it('should retain state styles when the underlying DOM structure changes even if there are insert/remove animations',
+         () => {
+           @Component({
+             selector: 'ani-cmp',
+             template: `
+            <div class="item" *ngFor="let item of items" [@color]="colorExp">
+              {{ item }}
+            </div>
+          `,
+             animations: [trigger(
+                 'color',
+                 [
+                   transition('* => *', animate(500)),
+                   state('green', style({backgroundColor: 'green'}))
+                 ])]
+           })
+           class Cmp {
+             public colorExp = 'green';
+             public items = [0, 1, 2, 3];
+
+             reorder() {
+               const temp = this.items[0];
+               this.items[0] = this.items[1];
+               this.items[1] = temp;
+             }
+           }
+
+           TestBed.configureTestingModule({declarations: [Cmp]});
+
+           const fixture = TestBed.createComponent(Cmp);
+           const cmp = fixture.componentInstance;
+           fixture.detectChanges();
+
+           getLog().forEach(p => p.finish());
+
+           let elements: HTMLElement[] = fixture.nativeElement.querySelectorAll('.item');
+           assertBackgroundColor(elements[0], 'green');
+           assertBackgroundColor(elements[1], 'green');
+           assertBackgroundColor(elements[2], 'green');
+           assertBackgroundColor(elements[3], 'green');
+
+           elements[0].title = '0a';
+           elements[1].title = '1a';
+
+           cmp.reorder();
+           fixture.detectChanges();
+
+           getLog().forEach(p => p.finish());
+
+           elements = fixture.nativeElement.querySelectorAll('.item');
+           assertBackgroundColor(elements[0], 'green');
+           assertBackgroundColor(elements[1], 'green');
+           assertBackgroundColor(elements[2], 'green');
+           assertBackgroundColor(elements[3], 'green');
+
+           function assertBackgroundColor(element: HTMLElement, color: string) {
+             expect(element.style.getPropertyValue('background-color')).toEqual(color);
+           }
+         });
+
       it('should animate removals of nodes to the `void` state for each animation trigger, but treat all auto styles as pre styles',
          () => {
            @Component({