fix(animations): capture cancelled animation styles within grouped animations

Closes #17170

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

@@ -5,7 +5,7 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-import {AUTO_STYLE, AnimationOptions, AnimationPlayer, NoopAnimationPlayer, ɵPRE_STYLE as PRE_STYLE, ɵStyleData} from '@angular/animations';
+import {AUTO_STYLE, AnimationOptions, AnimationPlayer, NoopAnimationPlayer, ɵAnimationGroupPlayer as AnimationGroupPlayer, ɵPRE_STYLE as PRE_STYLE, ɵStyleData} from '@angular/animations';
 
 import {AnimationTimelineInstruction} from '../dsl/animation_timeline_instruction';
 import {AnimationTransitionFactory} from '../dsl/animation_transition_factory';
@@ -1168,8 +1168,8 @@ export class TransitionAnimationEngine {
       if (details && details.removedBeforeQueried) return new NoopAnimationPlayer();
 
       const isQueriedElement = element !== rootElement;
-      const previousPlayers =
+      const previousPlayers = flattenGroupPlayers(
-          (allPreviousPlayersMap.get(element) || EMPTY_PLAYER_ARRAY).map(p => p.getRealPlayer());
+          (allPreviousPlayersMap.get(element) || EMPTY_PLAYER_ARRAY).map(p => p.getRealPlayer()));
 
       const preStyles = preStylesMap.get(element);
       const postStyles = postStylesMap.get(element);
@@ -1464,3 +1464,20 @@ function removeNodesAfterAnimationDone(
     engine: TransitionAnimationEngine, element: any, players: AnimationPlayer[]) {
   optimizeGroupPlayer(players).onDone(() => engine.processLeaveNode(element));
 }
+
+function flattenGroupPlayers(players: AnimationPlayer[]): AnimationPlayer[] {
+  const finalPlayers: AnimationPlayer[] = [];
+  _flattenGroupPlayersRecur(players, finalPlayers);
+  return finalPlayers;
+}
+
+function _flattenGroupPlayersRecur(players: AnimationPlayer[], finalPlayers: AnimationPlayer[]) {
+  for (let i = 0; i < players.length; i++) {
+    const player = players[i];
+    if (player instanceof AnimationGroupPlayer) {
+      _flattenGroupPlayersRecur(player.players, finalPlayers);
+    } else {
+      finalPlayers.push(player as AnimationPlayer);
+    }
+  }
+}

packages/animations/src/players/animation_group_player.ts

@@ -132,4 +132,12 @@ export class AnimationGroupPlayer implements AnimationPlayer {
   }
 
   get players(): AnimationPlayer[] { return this._players; }
+
+  beforeDestroy(): void {
+    this.players.forEach(player => {
+      if (player.beforeDestroy) {
+        player.beforeDestroy();
+      }
+    });
+  }
 }

packages/core/test/animation/animation_integration_spec.ts

@@ -799,6 +799,75 @@ export function main() {
            expect(p3.previousStyles).toEqual({});
          });
 
+      it('should provide the styling of previous players that are grouped', () => {
+        @Component({
+          selector: 'ani-cmp',
+          template: `
+          <div [@myAnimation]="exp"></div>
+        `,
+          animations: [trigger(
+              'myAnimation',
+              [
+                transition(
+                    '1 => 2',
+                    [
+                      group([
+                        animate(500, style({'width': '100px'})),
+                        animate(500, style({'height': '100px'})),
+                      ]),
+                      animate(500, keyframes([
+                        style({'opacity': '0'}),
+                        style({'opacity': '1'})
+                      ]))
+                    ]),
+                transition(
+                    '2 => 3',
+                    [
+                      style({'opacity': '0'}),
+                      animate(500, style({'opacity': '1'})),
+                    ]),
+              ])],
+        })
+        class Cmp {
+          exp: any = false;
+        }
+
+        TestBed.configureTestingModule({declarations: [Cmp]});
+
+        const engine = TestBed.get(ɵAnimationEngine);
+        const fixture = TestBed.createComponent(Cmp);
+        const cmp = fixture.componentInstance;
+
+        fixture.detectChanges();
+        engine.flush();
+
+        cmp.exp = '1';
+        fixture.detectChanges();
+        engine.flush();
+        expect(getLog().length).toEqual(0);
+        resetLog();
+
+        cmp.exp = '2';
+        fixture.detectChanges();
+        engine.flush();
+        expect(getLog().length).toEqual(3);
+        resetLog();
+
+        cmp.exp = '3';
+        fixture.detectChanges();
+        engine.flush();
+
+        const players = getLog();
+        expect(players.length).toEqual(1);
+        const player = players[0] as MockAnimationPlayer;
+        const pp = player.previousPlayers as MockAnimationPlayer[];
+
+        expect(pp.length).toEqual(3);
+        expect(pp[0].currentSnapshot).toEqual({width: AUTO_STYLE});
+        expect(pp[1].currentSnapshot).toEqual({height: AUTO_STYLE});
+        expect(pp[2].currentSnapshot).toEqual({opacity: AUTO_STYLE});
+      });
+
       it('should properly balance styles between states even if there are no destination state styles',
          () => {
            @Component({