Support custom events and non-bubbling standard events (#722)

* Support non-bubbling events

* Support responding to arbitrary events. E2E coverage of this and bubbling.

* Rename E2E test files to avoid clash with other PR

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Rendering/EventDelegator.ts

@@ -1,5 +1,10 @@
 import { EventForDotNet, UIEventArgs } from './EventForDotNet';
 
+const nonBubblingEvents = toLookup([
+  'abort', 'blur', 'change', 'error', 'focus', 'load', 'loadend', 'loadstart', 'mouseenter', 'mouseleave',
+  'progress', 'reset', 'scroll', 'submit', 'unload', 'DOMNodeInsertedIntoDocument', 'DOMNodeRemovedFromDocument'
+]);
+
 export interface OnEventCallback {
   (event: Event, componentId: number, eventHandlerId: number, eventArgs: EventForDotNet<UIEventArgs>): void;
 }
@@ -64,6 +69,7 @@ export class EventDelegator {
     // Scan up the element hierarchy, looking for any matching registered event handlers
     let candidateElement = evt.target as Element | null;
     let eventArgs: EventForDotNet<UIEventArgs> | null = null; // Populate lazily
+    const eventIsNonBubbling = nonBubblingEvents.hasOwnProperty(evt.type);
     while (candidateElement) {
       if (candidateElement.hasOwnProperty(this.eventsCollectionKey)) {
         const handlerInfos = candidateElement[this.eventsCollectionKey];
@@ -78,7 +84,7 @@ export class EventDelegator {
         }
       }
 
-      candidateElement = candidateElement.parentElement;
+      candidateElement = eventIsNonBubbling ? null : candidateElement.parentElement;
     }
   }
 }
@@ -105,7 +111,11 @@ class EventInfoStore {
       this.countByEventName[eventName]++;
     } else {
       this.countByEventName[eventName] = 1;
-      document.addEventListener(eventName, this.globalListener);
+
+      // To make delegation work with non-bubbling events, register a 'capture' listener.
+      // We preserve the non-bubbling behavior by only dispatching such events to the targeted element.
+      const useCapture = nonBubblingEvents.hasOwnProperty(eventName);
+      document.addEventListener(eventName, this.globalListener, useCapture);
     }
   }
 
@@ -154,3 +164,9 @@ interface EventHandlerInfo {
   componentId: number;
   eventHandlerId: number;
 }
+
+function toLookup(items: string[]): { [key: string]: boolean } {
+  const result = {};
+  items.forEach(value => { result[value] = true; });
+  return result;
+}

src/Microsoft.AspNetCore.Blazor.Browser/Rendering/BrowserRendererEventDispatcher.cs

@@ -38,6 +38,8 @@ namespace Microsoft.AspNetCore.Blazor.Browser.Rendering
                     return JsonUtil.Deserialize<UIKeyboardEventArgs>(eventArgsJson);
                 case "change":
                     return JsonUtil.Deserialize<UIChangeEventArgs>(eventArgsJson);
+                case "unknown":
+                    return JsonUtil.Deserialize<UIEventArgs>(eventArgsJson);
                 default:
                     throw new ArgumentException($"Unsupported value '{eventArgsType}'.", nameof(eventArgsType));
             }

test/Microsoft.AspNetCore.Blazor.E2ETest/Tests/EventBubblingTest.cs

@@ -0,0 +1,109 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using BasicTestApp;
+using Microsoft.AspNetCore.Blazor.E2ETest.Infrastructure;
+using Microsoft.AspNetCore.Blazor.E2ETest.Infrastructure.ServerFixtures;
+using OpenQA.Selenium;
+using System;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.AspNetCore.Blazor.E2ETest.Tests
+{
+    public class EventBubblingTest : BasicTestAppTestBase
+    {
+        // Note that currently we only support custom events if they have bubble:true.
+        // That's because the event delegator doesn't know which custom events bubble and which don't,
+        // so it doesn't know whether to register a normal handler or a capturing one. If this becomes
+        // a problem, we could consider registering both types of handler and just bailing out from
+        // the one that doesn't match the 'bubbles' flag on the received event object.
+
+        public EventBubblingTest(
+            BrowserFixture browserFixture, 
+            DevHostServerFixture<Program> serverFixture,
+            ITestOutputHelper output)
+            : base(browserFixture, serverFixture, output)
+        {
+            Navigate(ServerPathBase, noReload: true);
+            MountTestComponent<EventBubblingComponent>();
+        }
+        
+        [Fact]
+        public void BubblingStandardEvent_FiredOnElementWithHandler()
+        {
+            Browser.FindElement(By.Id("button-with-onclick")).Click();
+
+            // Triggers event on target and ancestors with handler in upwards direction
+            Assert.Equal(
+                new[] { "target onclick", "parent onclick" },
+                GetLogLines());
+        }
+
+        [Fact]
+        public void BubblingStandardEvent_FiredOnElementWithoutHandler()
+        {
+            Browser.FindElement(By.Id("button-without-onclick")).Click();
+
+            // Triggers event on ancestors with handler in upwards direction
+            Assert.Equal(
+                new[] { "parent onclick" },
+                GetLogLines());
+        }
+
+        [Fact]
+        public void BubblingCustomEvent_FiredOnElementWithHandler()
+        {
+            TriggerCustomBubblingEvent("element-with-onsneeze", "sneeze");
+
+            // Triggers event on target and ancestors with handler in upwards direction
+            Assert.Equal(
+                new[] { "target onsneeze", "parent onsneeze" },
+                GetLogLines());
+        }
+
+        [Fact]
+        public void BubblingCustomEvent_FiredOnElementWithoutHandler()
+        {
+            TriggerCustomBubblingEvent("element-without-onsneeze", "sneeze");
+
+            // Triggers event on ancestors with handler in upwards direction
+            Assert.Equal(
+                new[] { "parent onsneeze" },
+                GetLogLines());
+        }
+
+        [Fact]
+        public void NonBubblingEvent_FiredOnElementWithHandler()
+        {
+            Browser.FindElement(By.Id("input-with-onfocus")).Click();
+
+            // Triggers event only on target, not other ancestors with event handler
+            Assert.Equal(new[] { "target onfocus" }, GetLogLines());
+        }
+
+        [Fact]
+        public void NonBubblingEvent_FiredOnElementWithoutHandler()
+        {
+            Browser.FindElement(By.Id("input-without-onfocus")).Click();
+
+            // Triggers no event
+            Assert.Empty(GetLogLines());
+        }
+
+        private string[] GetLogLines()
+            => Browser.FindElement(By.TagName("textarea"))
+            .GetAttribute("value")
+            .Replace("\r\n", "\n")
+            .Split('\n', StringSplitOptions.RemoveEmptyEntries);
+
+        private void TriggerCustomBubblingEvent(string elementId, string eventName)
+        {
+            var jsExecutor = (IJavaScriptExecutor)Browser;
+            jsExecutor.ExecuteScript(
+                $"document.getElementById('{elementId}').dispatchEvent(" +
+                $"    new Event('{eventName}', {{ bubbles: true }})" +
+                $")");
+        }
+    }
+}

test/testapps/BasicTestApp/EventBubblingComponent.cshtml

@@ -0,0 +1,34 @@
+<h3>Bubbling standard event</h3>
+
+<div onclick="@(() => LogEvent("parent onclick"))">
+    <button id="button-with-onclick" onclick="@(() => LogEvent("target onclick"))">Button with onclick handler</button>
+    <button id="button-without-onclick" >Button without onclick handler</button>
+</div>
+
+<h3>Bubbling custom event</h3>
+
+<div onsneeze="@(new Action(() => LogEvent("parent onsneeze")))">
+    <div id="element-with-onsneeze" onsneeze="@(new Action(() => LogEvent("target onsneeze")))">Element with onsneeze handler</div>
+    <div id="element-without-onsneeze" >Element without onsneeze handler</div>
+</div>
+
+<h3>Non-bubbling standard event</h3>
+
+<!-- The new Action(...) is needed until we add support for onfocus -->
+<div onfocus="@(new Action(() => LogEvent("parent onfocus")))">
+    <p>With onfocus: <input id="input-with-onfocus" onfocus="@(new Action(() => LogEvent("target onfocus")))" /></p>
+    <p>Without onfocus: <input id="input-without-onfocus" /></p>
+</div>
+
+<h3>Event log</h3>
+
+<textarea readonly bind="@logValue"></textarea>
+
+@functions {
+    string logValue = string.Empty;
+
+    void LogEvent(string message)
+    {
+        logValue += message + Environment.NewLine;
+    }
+}

test/testapps/BasicTestApp/wwwroot/index.html

@@ -32,6 +32,7 @@
       <option value="BasicTestApp.ElementRefComponent">Element ref component</option>
       <option value="BasicTestApp.ComponentRefComponent">Component ref component</option>
       <option value="BasicTestApp.AfterRenderInteropComponent">After-render interop component</option>
+      <option value="BasicTestApp.EventCasesComponent">Event cases</option>
       <!--<option value="BasicTestApp.RouterTest.Default">Router</option> Excluded because it requires additional setup to work correctly when loaded manually -->
     </select>
     &nbsp;