From 2602b039b4bbb4d1a77a576c67dda6c7f22cfd39 Mon Sep 17 00:00:00 2001
From: Tobias Bosch <tbosch1009@gmail.com>
Date: Fri, 24 Feb 2017 16:28:14 -0800
Subject: [PATCH] fix(animations): ignore triggers that are registered multiple
 times (#14723)

---
 .../animations/src/render/dom_animation_engine.ts         | 4 ++--
 .../animations/src/render/noop_animation_engine.ts        | 8 ++++++--
 .../animations/test/engine/dom_animation_engine_spec.ts   | 6 ++----
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/modules/@angular/platform-browser/animations/src/render/dom_animation_engine.ts b/modules/@angular/platform-browser/animations/src/render/dom_animation_engine.ts
index c13e834124..7b9372e69f 100644
--- a/modules/@angular/platform-browser/animations/src/render/dom_animation_engine.ts
+++ b/modules/@angular/platform-browser/animations/src/render/dom_animation_engine.ts
@@ -40,7 +40,7 @@ export class DomAnimationEngine {
 
   private _elementTriggerStates = new Map<any, {[triggerName: string]: string}>();
 
-  private _triggers: {[triggerName: string]: AnimationTrigger} = {};
+  private _triggers: {[triggerName: string]: AnimationTrigger} = Object.create(null);
   private _triggerListeners = new Map<any, TriggerListenerTuple[]>();
 
   constructor(private _driver: AnimationDriver, private _normalizer: AnimationStyleNormalizer) {}
@@ -58,7 +58,7 @@ export class DomAnimationEngine {
   registerTrigger(trigger: AnimationTriggerMetadata, name: string = null): void {
     name = name || trigger.name;
     if (this._triggers[name]) {
-      throw new Error(`The provided animation trigger "${name}" has already been registered!`);
+      return;
     }
     this._triggers[name] = buildTrigger(name, trigger.definitions);
   }
diff --git a/modules/@angular/platform-browser/animations/src/render/noop_animation_engine.ts b/modules/@angular/platform-browser/animations/src/render/noop_animation_engine.ts
index 3818c25655..58100c0d2d 100644
--- a/modules/@angular/platform-browser/animations/src/render/noop_animation_engine.ts
+++ b/modules/@angular/platform-browser/animations/src/render/noop_animation_engine.ts
@@ -32,9 +32,14 @@ export class NoopAnimationEngine extends AnimationEngine {
   private _changes: ChangeTuple[] = [];
   private _flaggedRemovals = new Set<any>();
   private _onDoneFns: (() => any)[] = [];
-  private _triggerStyles: {[triggerName: string]: {[stateName: string]: ɵStyleData}} = {};
+  private _triggerStyles: {[triggerName: string]: {[stateName: string]: ɵStyleData}} =
+      Object.create(null);
 
   registerTrigger(trigger: AnimationTriggerMetadata, name: string = null): void {
+    name = name || trigger.name;
+    if (this._triggerStyles[name]) {
+      return;
+    }
     const stateMap: {[stateName: string]: ɵStyleData} = {};
     trigger.definitions.forEach(def => {
       if (def.type === AnimationMetadataType.State) {
@@ -42,7 +47,6 @@ export class NoopAnimationEngine extends AnimationEngine {
         stateMap[stateDef.name] = normalizeStyles(stateDef.styles.styles);
       }
     });
-    name = name || trigger.name;
     this._triggerStyles[name] = stateMap;
   }
 
diff --git a/modules/@angular/platform-browser/animations/test/engine/dom_animation_engine_spec.ts b/modules/@angular/platform-browser/animations/test/engine/dom_animation_engine_spec.ts
index 900347484c..3829b10113 100644
--- a/modules/@angular/platform-browser/animations/test/engine/dom_animation_engine_spec.ts
+++ b/modules/@angular/platform-browser/animations/test/engine/dom_animation_engine_spec.ts
@@ -39,12 +39,10 @@ export function main() {
     }
 
     describe('trigger registration', () => {
-      it('should throw an error if the same trigger is registered twice', () => {
+      it('should ignore and not throw an error if the same trigger is registered twice', () => {
         const engine = makeEngine();
         engine.registerTrigger(trigger('trig', []));
-        expect(() => {
-          engine.registerTrigger(trigger('trig', []));
-        }).toThrowError(/The provided animation trigger "trig" has already been registered!/);
+        expect(() => { engine.registerTrigger(trigger('trig', [])); }).not.toThrow();
       });
     });