perf(ivy): coalesce handlers for events with the same name on the same element (#29786)

PR Close #29786

packages/core/src/render3/instructions/listener.ts

@@ -11,7 +11,7 @@ import {assertDataInRange} from '../../util/assert';
 import {isObservable} from '../../util/lang';
 import {PropertyAliasValue, TNode, TNodeFlags, TNodeType} from '../interfaces/node';
 import {GlobalTargetResolver, RElement, Renderer3, isProceduralRenderer} from '../interfaces/renderer';
-import {FLAGS, LView, LViewFlags, RENDERER, TVIEW} from '../interfaces/view';
+import {CLEANUP, FLAGS, LView, LViewFlags, RENDERER, TVIEW} from '../interfaces/view';
 import {assertNodeOfPossibleTypes} from '../node_assert';
 import {getLView, getPreviousOrParentTNode} from '../state';
 import {getComponentViewByIndex, getNativeByTNode, unwrapRNode} from '../util/view_utils';
@@ -64,6 +64,36 @@ export function ΔcomponentHostSyntheticListener<T>(
   listenerInternal(eventName, listenerFn, useCapture, eventTargetResolver, loadComponentRenderer);
 }
 
+/**
+ * A utility function that checks if a given element has already an event handler registered for an
+ * event with a specified name. The TView.cleanup data structure is used to find out which events
+ * are registered for a given element.
+ */
+function findExistingListener(
+    lView: LView, eventName: string, tNodeIdx: number): ((e?: any) => any)|null {
+  const tView = lView[TVIEW];
+  const tCleanup = tView.cleanup;
+  if (tCleanup != null) {
+    for (let i = 0; i < tCleanup.length - 1; i += 2) {
+      if (tCleanup[i] === eventName && tCleanup[i + 1] === tNodeIdx) {
+        // We have found a matching event name on the same node but it might not have been
+        // registered yet, so we must explicitly verify entries in the LView cleanup data
+        // structures.
+        const lCleanup = lView[CLEANUP] !;
+        const listenerIdxInLCleanup = tCleanup[i + 2];
+        return lCleanup.length > listenerIdxInLCleanup ? lCleanup[listenerIdxInLCleanup] : null;
+      }
+      // TView.cleanup can have a mix of 4-elements entries (for event handler cleanups) or
+      // 2-element entries (for directive and queries destroy hooks). As such we can encounter
+      // blocks of 4 or 2 items in the tView.cleanup and this is why we iterate over 2 elements
+      // first and jump another 2 elements if we detect listeners cleanup (4 elements). Also check
+      // documentation of TView.cleanup for more details of this data structure layout.
+      i += 2;
+    }
+  }
+  return null;
+}
+
 function listenerInternal(
     eventName: string, listenerFn: (e?: any) => any, useCapture = false,
     eventTargetResolver?: GlobalTargetResolver,
@@ -82,32 +112,56 @@ function listenerInternal(
     const native = getNativeByTNode(tNode, lView) as RElement;
     const resolved = eventTargetResolver ? eventTargetResolver(native) : {} as any;
     const target = resolved.target || native;
-    ngDevMode && ngDevMode.rendererAddEventListener++;
     const renderer = loadRendererFn ? loadRendererFn(tNode, lView) : lView[RENDERER];
     const lCleanup = getCleanup(lView);
     const lCleanupIndex = lCleanup.length;
-    let useCaptureOrSubIdx: boolean|number = useCapture;
+    const idxOrTargetGetter = eventTargetResolver ?
+        (_lView: LView) => eventTargetResolver(unwrapRNode(_lView[tNode.index])).target :
+        tNode.index;
 
     // In order to match current behavior, native DOM event listeners must be added for all
     // events (including outputs).
     if (isProceduralRenderer(renderer)) {
+      // There might be cases where multiple directives on the same element try to register an event
+      // handler function for the same event. In this situation we want to avoid registration of
+      // several native listeners as each registration would be intercepted by NgZone and
+      // trigger change detection. This would mean that a single user action would result in several
+      // change detections being invoked. To avoid this situation we want to have only one call to
+      // native handler registration (for the same element and same type of event).
+      //
+      // In order to have just one native event handler in presence of multiple handler functions,
+      // we just register a first handler function as a native event listener and then chain
+      // (coalesce) other handler functions on top of the first native handler function.
+      //
+      // Please note that the coalescing described here doesn't happen for events specifying an
+      // alternative target (ex. (document:click)) - this is to keep backward compatibility with the
+      // view engine.
+      const existingListener =
+          eventTargetResolver ? null : findExistingListener(lView, eventName, tNode.index);
+      if (existingListener !== null) {
+        // Attach a new listener at the head of the coalesced listeners list.
+        (<any>listenerFn).__ngNextListenerFn__ = (<any>existingListener).__ngNextListenerFn__;
+        (<any>existingListener).__ngNextListenerFn__ = listenerFn;
+      } else {
         // The first argument of `listen` function in Procedural Renderer is:
         // - either a target name (as a string) in case of global target (window, document, body)
         // - or element reference (in all other cases)
         listenerFn = wrapListener(tNode, lView, listenerFn, false /** preventDefault */);
         const cleanupFn = renderer.listen(resolved.name || target, eventName, listenerFn);
+        ngDevMode && ngDevMode.rendererAddEventListener++;
+
         lCleanup.push(listenerFn, cleanupFn);
-      useCaptureOrSubIdx = lCleanupIndex + 1;
+        tCleanup && tCleanup.push(eventName, idxOrTargetGetter, lCleanupIndex, lCleanupIndex + 1);
+      }
+
     } else {
       listenerFn = wrapListener(tNode, lView, listenerFn, true /** preventDefault */);
       target.addEventListener(eventName, listenerFn, useCapture);
-      lCleanup.push(listenerFn);
-    }
+      ngDevMode && ngDevMode.rendererAddEventListener++;
 
-    const idxOrTargetGetter = eventTargetResolver ?
-        (_lView: LView) => eventTargetResolver(unwrapRNode(_lView[tNode.index])).target :
-        tNode.index;
-    tCleanup && tCleanup.push(eventName, idxOrTargetGetter, lCleanupIndex, useCaptureOrSubIdx);
+      lCleanup.push(listenerFn);
+      tCleanup && tCleanup.push(eventName, idxOrTargetGetter, lCleanupIndex, useCapture);
+    }
   }
 
   // subscribe to directive outputs
@@ -144,6 +198,15 @@ function listenerInternal(
   }
 }
 
+function executeListenerWithErrorHandling(lView: LView, listenerFn: (e?: any) => any, e: any): any {
+  try {
+    return listenerFn(e);
+  } catch (error) {
+    handleError(lView, error);
+    return false;
+  }
+}
+
 /**
  * Wraps an event listener with a function that marks ancestors dirty and prevents default behavior,
  * if applicable.
@@ -170,16 +233,21 @@ function wrapListener(
       markViewDirty(startView);
     }
 
-    try {
-      const result = listenerFn(e);
+    let result = executeListenerWithErrorHandling(lView, listenerFn, e);
+    // A just-invoked listener function might have coalesced listeners so we need to check for
+    // their presence and invoke as needed.
+    let nextListenerFn = (<any>wrapListenerIn_markDirtyAndPreventDefault).__ngNextListenerFn__;
+    while (nextListenerFn) {
+      result = executeListenerWithErrorHandling(lView, nextListenerFn, e);
+      nextListenerFn = (<any>nextListenerFn).__ngNextListenerFn__;
+    }
+
     if (wrapWithPreventDefault && result === false) {
       e.preventDefault();
       // Necessary for legacy browsers that don't support preventDefault (e.g. IE)
       e.returnValue = false;
     }
+
     return result;
-    } catch (error) {
-      handleError(lView, error);
-    }
   };
 }

packages/core/test/acceptance/listener_spec.ts

@@ -0,0 +1,123 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * 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 {Component, Directive, ErrorHandler, HostListener} from '@angular/core';
+import {TestBed} from '@angular/core/testing';
+import {By} from '@angular/platform-browser';
+import {onlyInIvy} from '@angular/private/testing';
+
+function getNoOfNativeListeners(): number {
+  return ngDevMode ? ngDevMode.rendererAddEventListener : 0;
+}
+
+describe('event listeners', () => {
+
+  describe('coalescing', () => {
+
+    @Component({
+      selector: 'with-clicks-cmpt',
+      template: `<button likes-clicks (click)="count()" md-button>Click me!</button>`
+    })
+    class WithClicksCmpt {
+      counter = 0;
+      count() { this.counter++; }
+    }
+
+    @Directive({selector: '[md-button]'})
+    class MdButton {
+      counter = 0;
+      @HostListener('click')
+      count() { this.counter++; }
+    }
+
+    @Directive({selector: '[likes-clicks]'})
+    class LikesClicks {
+      counter = 0;
+      @HostListener('click')
+      count() { this.counter++; }
+    }
+
+    onlyInIvy('ngDevMode.rendererAddEventListener counters are only available in ivy')
+        .it('should coalesce multiple event listeners for the same event on the same element',
+            () => {
+
+              @Component({
+                selector: 'test-cmpt',
+                template:
+                    `<with-clicks-cmpt></with-clicks-cmpt><with-clicks-cmpt></with-clicks-cmpt>`
+              })
+              class TestCmpt {
+              }
+
+              TestBed.configureTestingModule(
+                  {declarations: [TestCmpt, WithClicksCmpt, LikesClicks, MdButton]});
+              const noOfEventListenersRegisteredSoFar = getNoOfNativeListeners();
+              const fixture = TestBed.createComponent(TestCmpt);
+              fixture.detectChanges();
+              const buttonDebugEls = fixture.debugElement.queryAll(By.css('button'));
+              const withClicksEls = fixture.debugElement.queryAll(By.css('with-clicks-cmpt'));
+
+              // We want to assert that only one native event handler was registered but still all
+              // directives are notified when an event fires. This assertion can only be verified in
+              // the ngDevMode (but the coalescing always happens!).
+              ngDevMode &&
+                  expect(getNoOfNativeListeners()).toBe(noOfEventListenersRegisteredSoFar + 2);
+
+              buttonDebugEls[0].nativeElement.click();
+              expect(withClicksEls[0].injector.get(WithClicksCmpt).counter).toBe(1);
+              expect(buttonDebugEls[0].injector.get(LikesClicks).counter).toBe(1);
+              expect(buttonDebugEls[0].injector.get(MdButton).counter).toBe(1);
+              expect(withClicksEls[1].injector.get(WithClicksCmpt).counter).toBe(0);
+              expect(buttonDebugEls[1].injector.get(LikesClicks).counter).toBe(0);
+              expect(buttonDebugEls[1].injector.get(MdButton).counter).toBe(0);
+
+              buttonDebugEls[1].nativeElement.click();
+              expect(withClicksEls[0].injector.get(WithClicksCmpt).counter).toBe(1);
+              expect(buttonDebugEls[0].injector.get(LikesClicks).counter).toBe(1);
+              expect(buttonDebugEls[0].injector.get(MdButton).counter).toBe(1);
+              expect(withClicksEls[1].injector.get(WithClicksCmpt).counter).toBe(1);
+              expect(buttonDebugEls[1].injector.get(LikesClicks).counter).toBe(1);
+              expect(buttonDebugEls[1].injector.get(MdButton).counter).toBe(1);
+            });
+
+
+    it('should try to execute remaining coalesced listeners if one of the listeners throws', () => {
+
+      @Directive({selector: '[throws-on-clicks]'})
+      class ThrowsOnClicks {
+        @HostListener('click')
+        dontCount() { throw new Error('I was clicked and I don\'t like it!'); }
+      }
+
+      @Component(
+          {selector: 'test-cmpt', template: `<button throws-on-clicks likes-clicks><button>`})
+      class TestCmpt {
+      }
+
+      let noOfErrors = 0;
+
+      class CountingErrorHandler extends ErrorHandler {
+        handleError(error: any): void { noOfErrors++; }
+      }
+
+      TestBed.configureTestingModule({
+        declarations: [TestCmpt, LikesClicks, ThrowsOnClicks],
+        providers: [{provide: ErrorHandler, useClass: CountingErrorHandler}]
+      });
+      const fixture = TestBed.createComponent(TestCmpt);
+      fixture.detectChanges();
+      const buttonDebugEl = fixture.debugElement.query(By.css('button'));
+
+      expect(buttonDebugEl.injector.get(LikesClicks).counter).toBe(0);
+
+      buttonDebugEl.nativeElement.click();
+      expect(noOfErrors).toBe(1);
+      expect(buttonDebugEl.injector.get(LikesClicks).counter).toBe(1);
+    });
+  });
+});

packages/core/test/bundling/todo/bundle.golden_symbols.json

@@ -581,6 +581,9 @@
   {
     "name": "executeHooks"
   },
+  {
+    "name": "executeListenerWithErrorHandling"
+  },
   {
     "name": "executeNodeAction"
   },
@@ -611,6 +614,9 @@
   {
     "name": "findDirectiveMatches"
   },
+  {
+    "name": "findExistingListener"
+  },
   {
     "name": "findOrPatchDirectiveIntoRegistry"
   },