fix(ripple): Prevent ancestors of nested ripple surfaces from activat…

…ing (#2123)

packages/mdc-ripple/foundation.js

@@ -66,6 +66,9 @@ const ACTIVATION_EVENT_TYPES = ['touchstart', 'pointerdown', 'mousedown', 'keydo
 // Deactivation events registered on documentElement when a pointer-related down event occurs
 const POINTER_DEACTIVATION_EVENT_TYPES = ['touchend', 'pointerup', 'mouseup'];
 
+// Tracks whether an activation has occurred on the current frame, to avoid multiple nested activations
+let isActivating = false;
+
 /**
  * @extends {MDCFoundation<!MDCRippleAdapter>}
  */
@@ -281,7 +284,7 @@ class MDCRippleFoundation extends MDCFoundation {
    * @private
    */
   activate_(e) {
-    if (this.adapter_.isSurfaceDisabled()) {
+    if (isActivating || this.adapter_.isSurfaceDisabled()) {
       return;
     }
 
@@ -308,6 +311,7 @@ class MDCRippleFoundation extends MDCFoundation {
       this.registerDeactivationHandlers_(e);
     }
 
+    isActivating = true;
     requestAnimationFrame(() => {
       // This needs to be wrapped in an rAF call b/c web browsers
       // report active states inconsistently when they're called within
@@ -321,6 +325,9 @@ class MDCRippleFoundation extends MDCFoundation {
         // Reset activation state immediately if element was not made active.
         this.activationState_ = this.defaultActivationState_();
       }
+
+      // Reset flag on next frame to avoid any ancestors from also triggering ripple from the same interaction
+      isActivating = false;
     });
   }
 

test/unit/mdc-ripple/foundation-activation.test.js

@@ -17,7 +17,7 @@
 import td from 'testdouble';
 
 import {captureHandlers} from '../helpers/foundation';
-import {testFoundation} from './helpers';
+import {setupTest, testFoundation} from './helpers';
 import {cssClasses, strings, numbers} from '../../../packages/mdc-ripple/constants';
 
 suite('MDCRippleFoundation - Activation Logic');
@@ -318,6 +318,25 @@ testFoundation('removes deactivation classes on activate to ensure ripples can b
     td.verify(adapter.removeClass(cssClasses.FG_DEACTIVATION));
   });
 
+testFoundation('will not activate multiple ripples on same frame',
+  ({foundation, adapter, mockRaf}) => {
+    const secondRipple = setupTest();
+    const firstHandlers = captureHandlers(adapter, 'registerInteractionHandler');
+    const secondHandlers = captureHandlers(secondRipple.adapter, 'registerInteractionHandler');
+    foundation.init();
+    secondRipple.foundation.init();
+    mockRaf.flush();
+
+    // Simulate use case where a child and parent are both ripple surfaces, and the same event propagates to the
+    // parent after being handled on the child
+    firstHandlers.mousedown();
+    secondHandlers.mousedown();
+    mockRaf.flush();
+
+    td.verify(adapter.addClass(cssClasses.FG_ACTIVATION));
+    td.verify(secondRipple.adapter.addClass(cssClasses.FG_ACTIVATION), {times: 0});
+  });
+
 testFoundation('displays the foreground ripple on activation when unbounded', ({foundation, adapter, mockRaf}) => {
   const handlers = captureHandlers(adapter, 'registerInteractionHandler');
   td.when(adapter.computeBoundingRect()).thenReturn({width: 100, height: 100, left: 0, top: 0});