Add optional error boundary support (#473)

* Add support for exception handling during component render

* Add tests and update sample

* Fix newline/whitespace issues

* Support component-level exception handlers

* Document exceptionHandler arguments

Author: dustinsoftware

src/React.AspNet/HtmlHelperExtensions.cs

@@ -7,6 +7,7 @@
  *  of patent rights can be found in the PATENTS file in the same directory.
  */
 
+using System;
 using React.Exceptions;
 using React.TinyIoC;
 
@@ -55,6 +56,7 @@ private static IReactEnvironment Environment
 		/// <param name="clientOnly">Skip rendering server-side and only output client-side initialisation code. Defaults to <c>false</c></param>
 		/// <param name="serverOnly">Skip rendering React specific data-attributes during server side rendering. Defaults to <c>false</c></param>
 		/// <param name="containerClass">HTML class(es) to set on the container tag</param>
+		/// <param name="exceptionHandler">A custom exception handler that will be called if a component throws during a render. Args: (Exception ex, string componentName, string containerId)</param>
 		/// <returns>The component's HTML</returns>
 		public static IHtmlString React<T>(
 			this IHtmlHelper htmlHelper,
@@ -64,7 +66,8 @@ public static IHtmlString React<T>(
 			string containerId = null,
 			bool clientOnly = false,
 			bool serverOnly = false,
-			string containerClass = null
+			string containerClass = null,
+			Action<Exception, string, string> exceptionHandler = null
 		)
 		{
 			try
@@ -78,7 +81,7 @@ public static IHtmlString React<T>(
 				{
 					reactComponent.ContainerClass = containerClass;
 				}
-				var result = reactComponent.RenderHtml(clientOnly, serverOnly);
+				var result = reactComponent.RenderHtml(clientOnly, serverOnly, exceptionHandler);
 				return new HtmlString(result);
 			}
 			finally
@@ -100,6 +103,7 @@ public static IHtmlString React<T>(
 		/// <param name="containerId">ID to use for the container HTML tag. Defaults to an auto-generated ID</param>
 		/// <param name="clientOnly">Skip rendering server-side and only output client-side initialisation code. Defaults to <c>false</c></param>
 		/// <param name="containerClass">HTML class(es) to set on the container tag</param>
+		/// <param name="exceptionHandler">A custom exception handler that will be called if a component throws during a render. Args: (Exception ex, string componentName, string containerId)</param>
 		/// <returns>The component's HTML</returns>
 		public static IHtmlString ReactWithInit<T>(
 			this IHtmlHelper htmlHelper,
@@ -108,7 +112,8 @@ public static IHtmlString ReactWithInit<T>(
 			string htmlTag = null,
 			string containerId = null,
 			bool clientOnly = false,
-			string containerClass = null
+			string containerClass = null,
+			Action<Exception, string, string> exceptionHandler = null
 		)
 		{
 			try
@@ -122,7 +127,7 @@ public static IHtmlString ReactWithInit<T>(
 				{
 					reactComponent.ContainerClass = containerClass;
 				}
-				var html = reactComponent.RenderHtml(clientOnly);
+				var html = reactComponent.RenderHtml(clientOnly, exceptionHandler: exceptionHandler);
 
 #if LEGACYASPNET
 				var script = new TagBuilder("script")

src/React.Core/IReactComponent.cs

@@ -1,4 +1,4 @@
-/*
+/*
  *  Copyright (c) 2014-Present, Facebook, Inc.
  *  All rights reserved.
  *
@@ -7,6 +7,8 @@
  *  of patent rights can be found in the PATENTS file in the same directory.
  */
 
+using System;
+
 namespace React
 {
 	/// <summary>
@@ -45,8 +47,9 @@ public interface IReactComponent
 		/// </summary>
 		/// <param name="renderContainerOnly">Only renders component container. Used for client-side only rendering.</param>
 		/// <param name="renderServerOnly">Only renders the common HTML mark up and not any React specific data attributes. Used for server-side only rendering.</param>
+		/// <param name="exceptionHandler">A custom exception handler that will be called if a component throws during a render. Args: (Exception ex, string componentName, string containerId)</param>
 		/// <returns>HTML</returns>
-		string RenderHtml(bool renderContainerOnly = false, bool renderServerOnly = false);
+		string RenderHtml(bool renderContainerOnly = false, bool renderServerOnly = false, Action<Exception, string, string> exceptionHandler = null);
 
 		/// <summary>
 		/// Renders the JavaScript required to initialise this component client-side. This will

src/React.Core/IReactSiteConfiguration.cs

@@ -1,4 +1,4 @@
-/*
+/*
  *  Copyright (c) 2014-Present, Facebook, Inc.
  *  All rights reserved.
  *
@@ -179,5 +179,19 @@ public interface IReactSiteConfiguration
 		/// Disables server-side rendering. This is useful when debugging your scripts.
 		/// </summary>
 		IReactSiteConfiguration DisableServerSideRendering();
+
+		/// <summary>
+		/// An exception handler which will be called if a render exception is thrown.
+		/// If unset, unhandled exceptions will be thrown for all component renders.
+		/// </summary>
+		Action<Exception, string, string> ExceptionHandler { get; set; }
+
+		/// <summary>
+		/// Sets an exception handler which will be called if a render exception is thrown.
+		/// If unset, unhandled exceptions will be thrown for all component renders.
+		/// </summary>
+		/// <param name="handler"></param>
+		/// <returns></returns>
+		IReactSiteConfiguration SetExceptionHandler(Action<Exception, string, string> handler);
 	}
 }

src/React.Core/ReactComponent.cs

@@ -1,4 +1,4 @@
-/*
+/*
  *  Copyright (c) 2014-Present, Facebook, Inc.
  *  All rights reserved.
  *
@@ -107,8 +107,9 @@ public ReactComponent(IReactEnvironment environment, IReactSiteConfiguration con
 		/// </summary>
 		/// <param name="renderContainerOnly">Only renders component container. Used for client-side only rendering.</param>
 		/// <param name="renderServerOnly">Only renders the common HTML mark up and not any React specific data attributes. Used for server-side only rendering.</param>
+		/// <param name="exceptionHandler">A custom exception handler that will be called if a component throws during a render. Args: (Exception ex, string componentName, string containerId)</param>
 		/// <returns>HTML</returns>
-		public virtual string RenderHtml(bool renderContainerOnly = false, bool renderServerOnly = false)
+		public virtual string RenderHtml(bool renderContainerOnly = false, bool renderServerOnly = false, Action<Exception, string, string> exceptionHandler = null)
 		{
 			if (!_configuration.UseServerSideRendering)
 			{
@@ -120,39 +121,39 @@ public virtual string RenderHtml(bool renderContainerOnly = false, bool renderSe
 				EnsureComponentExists();
 			}
 
-			try
+			var html = string.Empty;
+			if (!renderContainerOnly)
 			{
-				var html = string.Empty;
-				if (!renderContainerOnly)
+				try
 				{
 					var reactRenderCommand = renderServerOnly
 						? string.Format("ReactDOMServer.renderToStaticMarkup({0})", GetComponentInitialiser())
 						: string.Format("ReactDOMServer.renderToString({0})", GetComponentInitialiser());
 					html = _environment.Execute<string>(reactRenderCommand);
 				}
-
-				string attributes = string.Format("id=\"{0}\"", ContainerId);
-				if (!string.IsNullOrEmpty(ContainerClass))
+				catch (JsRuntimeException ex)
 				{
-					attributes += string.Format(" class=\"{0}\"", ContainerClass);
-				}
+					if (exceptionHandler == null)
+					{
+						exceptionHandler = _configuration.ExceptionHandler;
+					}
 
-				return string.Format(
-					"<{2} {0}>{1}</{2}>",
-					attributes,
-					html,
-					ContainerTag
-				);
+					exceptionHandler(ex, ComponentName, ContainerId);
+				}
 			}
-			catch (JsRuntimeException ex)
+
+			string attributes = string.Format("id=\"{0}\"", ContainerId);
+			if (!string.IsNullOrEmpty(ContainerClass))
 			{
-				throw new ReactServerRenderingException(string.Format(
-					"Error while rendering \"{0}\" to \"{2}\": {1}",
-					ComponentName,
-					ex.Message,
-					ContainerId
-				));
+				attributes += string.Format(" class=\"{0}\"", ContainerClass);
 			}
+
+			return string.Format(
+				"<{2} {0}>{1}</{2}>",
+				attributes,
+				html,
+				ContainerTag
+			);
 		}
 
 		/// <summary>

src/React.Core/ReactSiteConfiguration.cs

@@ -1,4 +1,4 @@
-/*
+/*
  *  Copyright (c) 2014-Present, Facebook, Inc.
  *  All rights reserved.
  *
@@ -7,9 +7,11 @@
  *  of patent rights can be found in the PATENTS file in the same directory.
  */
 
-using Newtonsoft.Json;
+using System;
 using System.Collections.Generic;
 using System.Linq;
+using Newtonsoft.Json;
+using React.Exceptions;
 
 namespace React
 {
@@ -44,6 +46,13 @@ public ReactSiteConfiguration()
 			};
 			UseDebugReact = false;
 			UseServerSideRendering = true;
+			ExceptionHandler = (Exception ex, string ComponentName, string ContainerId) => 
+				throw new ReactServerRenderingException(string.Format(
+					"Error while rendering \"{0}\" to \"{2}\": {1}",
+					ComponentName,
+					ex.Message,
+					ContainerId
+				));
 		}
 
 		/// <summary>
@@ -300,5 +309,22 @@ public IReactSiteConfiguration DisableServerSideRendering()
 			UseServerSideRendering = false;
 			return this;
 		}
+
+		/// <summary>
+		/// Handle an exception caught during server-render of a component.
+		/// If unset, unhandled exceptions will be thrown for all component renders.
+		/// </summary>
+		public Action<Exception, string, string> ExceptionHandler { get; set; }
+
+		/// <summary>
+		/// 
+		/// </summary>
+		/// <param name="handler"></param>
+		/// <returns></returns>
+		public IReactSiteConfiguration SetExceptionHandler(Action<Exception, string, string> handler)
+		{
+			ExceptionHandler = handler;
+			return this;
+		}
 	}
 }

src/React.Sample.CoreMvc/Controllers/HomeController.cs

@@ -37,6 +37,7 @@ public class IndexViewModel
 	{
 		public IEnumerable<CommentModel> Comments { get; set; }
 		public int CommentsPerPage { get; set; }
+		public bool ThrowRenderError { get; set; }
 	}
 }
 
@@ -78,7 +79,8 @@ public IActionResult Index()
 			return View(new IndexViewModel
 			{
 				Comments = _comments.Take(COMMENTS_PER_PAGE),
-				CommentsPerPage = COMMENTS_PER_PAGE
+				CommentsPerPage = COMMENTS_PER_PAGE,
+				ThrowRenderError = Request.Query.ContainsKey("throwRenderError"),
 			});
 		}
 

src/React.Sample.CoreMvc/Startup.cs

@@ -5,8 +5,8 @@
  *  This source code is licensed under the BSD-style license found in the
  *  LICENSE file in the root directory of this source tree. An additional grant 
  *  of patent rights can be found in the PATENTS file in the same directory.
- */
-
+ */
+
 using System;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
@@ -20,15 +20,16 @@ namespace React.Sample.CoreMvc
 {
 	public class Startup
 	{
-		public Startup(IHostingEnvironment env)
+		public Startup(IHostingEnvironment env, ILogger<Startup> logger)
 		{
 			// Setup configuration sources.
 			var builder = new ConfigurationBuilder().AddEnvironmentVariables();
-
+			Logger = logger;
 			Configuration = builder.Build();
 		}
 
 		public IConfiguration Configuration { get; set; }
+		public ILogger<Startup> Logger { get; set; }
 
 		// This method gets called by the runtime.
 		public IServiceProvider ConfigureServices(IServiceCollection services)
@@ -70,6 +71,10 @@ public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerF
 				config
 					.SetReuseJavaScriptEngines(true)
 					.AddScript("~/js/Sample.jsx")
+					.SetExceptionHandler((ex, name, id) =>
+					{
+						Logger.LogError("React component exception thrown!" + ex.ToString());
+					})
 					.SetUseDebugReact(true);
 			});
 

src/React.Sample.CoreMvc/Views/Home/Index.cshtml

@@ -14,7 +14,7 @@
 </p>
 
 	<!-- Render the component server-side, passing initial props -->
-	@Html.React("CommentsBox", new { initialComments = Model.Comments })
+	@Html.React("CommentsBox", new { initialComments = Model.Comments, ThrowRenderError = Model.ThrowRenderError })
 
 	<!-- Load all required scripts (React + the site's scripts) -->
 	<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.0.0/umd/react.development.js"></script>

src/React.Sample.CoreMvc/wwwroot/js/Sample.jsx

@@ -9,7 +9,8 @@
 
 class CommentsBox extends React.Component {
 	static propTypes = {
-		initialComments: PropTypes.array.isRequired
+		initialComments: PropTypes.array.isRequired,
+		throwRenderError: PropTypes.bool,
 	};
 
 	state = {
@@ -53,6 +54,9 @@ class CommentsBox extends React.Component {
 					{commentNodes}
 				</ol>
 				{this.renderMoreLink()}
+				<ErrorBoundary>
+					<ExceptionDemo throwRenderError={this.props.throwRenderError} />
+				</ErrorBoundary>
 			</div>
 		);
 	}
@@ -108,3 +112,46 @@ class Avatar extends React.Component {
 		return 'https://avatars.githubusercontent.com/' + author.githubUsername + '?s=50';
 	}
 }
+
+class ErrorBoundary extends React.Component {
+	static propTypes = {
+		children: PropTypes.node.isRequired,
+	};
+
+	state = {};
+
+	componentDidCatch() {
+		this.setState({ hasCaughtException: true });
+	}
+
+	render() {
+		return this.state.hasCaughtException ? (
+			<div>An error occurred. Please reload.</div>
+		) : this.props.children;
+	}
+}
+
+class ExceptionDemo extends React.Component {
+	static propTypes = {
+		throwRenderError: PropTypes.bool,
+	}
+
+	state = {
+		throwRenderError: this.props.throwRenderError,
+	};
+
+	onClick = () => {
+		window.history.replaceState(null, null, window.location + '?throwRenderError');
+		this.setState({ throwRenderError: true });
+	}
+
+	render() {
+		return (
+			<div>
+				<button onClick={this.onClick}>
+					{this.state.throwRenderError ? this.state.testObject.one.two : ''}Throw exception
+				</button>
+			</div>
+		);
+	}
+}

tests/React.Tests/Core/ReactComponentTest.cs

@@ -1,15 +1,17 @@
-/*
+/*
  *  Copyright (c) 2014-Present, Facebook, Inc.
  *  All rights reserved.
  *
  *  This source code is licensed under the BSD-style license found in the
  *  LICENSE file in the root directory of this source tree. An additional grant
  *  of patent rights can be found in the PATENTS file in the same directory.
- */
-
+ */
+
+using System;
+using JavaScriptEngineSwitcher.Core;
 using Moq;
-using Xunit;
 using React.Exceptions;
+using Xunit;
 
 namespace React.Tests.Core
 {
@@ -160,7 +162,7 @@ public void RenderJavaScriptShouldCallRenderComponent()
 			);
 		}
 
-        [Theory]
+		[Theory]
 		[InlineData("Foo", true)]
 		[InlineData("Foo.Bar", true)]
 		[InlineData("Foo.Bar.Baz", true)]
@@ -192,5 +194,49 @@ public void GeneratesContainerIdIfNotProvided()
 			Assert.StartsWith("react_", component.ContainerId);
 		}
 
+		[Fact]
+		public void ExceptionThrownIsHandled()
+		{
+			var environment = new Mock<IReactEnvironment>();
+			environment.Setup(x => x.Execute<bool>("typeof Foo !== 'undefined'")).Returns(true);
+			environment.Setup(x => x.Execute<string>(@"ReactDOMServer.renderToString(React.createElement(Foo, {""hello"":""World""}))"))
+				.Throws(new JsRuntimeException("'undefined' is not an object"));
+
+			var config = new Mock<IReactSiteConfiguration>();
+			config.Setup(x => x.UseServerSideRendering).Returns(true);
+			config.Setup(x => x.ExceptionHandler).Returns(() => throw new ReactServerRenderingException("test"));
+
+			var component = new ReactComponent(environment.Object, config.Object, "Foo", "container")
+			{
+				Props = new { hello = "World" }
+			};
+
+			// Default behavior
+			bool exceptionCaught = false;
+			try
+			{
+				component.RenderHtml();
+			}
+			catch (ReactServerRenderingException)
+			{
+				exceptionCaught = true;
+			}
+
+			Assert.True(exceptionCaught);
+
+			// Custom handler passed into render call
+			bool customHandlerInvoked = false;
+			Action<Exception, string, string> customHandler = (ex, name, id) => customHandlerInvoked = true;
+			component.RenderHtml(exceptionHandler: customHandler);
+			Assert.True(customHandlerInvoked);
+			
+			// Custom exception handler set
+			Exception caughtException = null;
+			config.Setup(x => x.ExceptionHandler).Returns((ex, name, id) => caughtException = ex);
+
+			var result = component.RenderHtml();
+			Assert.Equal(@"<div id=""container""></div>", result);
+			Assert.NotNull(caughtException);
+		}
 	}
 }

tests/React.Tests/Mvc/HtmlHelperExtensionsTests.cs

@@ -5,11 +5,11 @@
  *  This source code is licensed under the BSD-style license found in the
  *  LICENSE file in the root directory of this source tree. An additional grant
  *  of patent rights can be found in the PATENTS file in the same directory.
- */
-
+ */
+
 using Moq;
-using Xunit;
 using React.Web.Mvc;
+using Xunit;
 
 namespace React.Tests.Mvc
 {
@@ -31,7 +31,7 @@ private Mock<IReactEnvironment> ConfigureMockEnvironment()
 		public void ReactWithInitShouldReturnHtmlAndScript()
 		{
 			var component = new Mock<IReactComponent>();
-			component.Setup(x => x.RenderHtml(false, false)).Returns("HTML");
+			component.Setup(x => x.RenderHtml(false, false, null)).Returns("HTML");
 			component.Setup(x => x.RenderJavaScript()).Returns("JS");
 			var environment = ConfigureMockEnvironment();
 			environment.Setup(x => x.CreateComponent(
@@ -57,7 +57,7 @@ public void ReactWithInitShouldReturnHtmlAndScript()
 		public void EngineIsReturnedToPoolAfterRender()
 		{
 			var component = new Mock<IReactComponent>();
-			component.Setup(x => x.RenderHtml(true, true)).Returns("HTML");
+			component.Setup(x => x.RenderHtml(true, true, null)).Returns("HTML");
 			var environment = ConfigureMockEnvironment();
 			environment.Setup(x => x.CreateComponent(
 				"ComponentName",
@@ -75,15 +75,15 @@ public void EngineIsReturnedToPoolAfterRender()
 				clientOnly: true,
 				serverOnly: true
 			);
-			component.Verify(x => x.RenderHtml(It.Is<bool>(y => y == true), It.Is<bool>(z => z == true)), Times.Once);
+			component.Verify(x => x.RenderHtml(It.Is<bool>(y => y == true), It.Is<bool>(z => z == true), null), Times.Once);
 			environment.Verify(x => x.ReturnEngineToPool(), Times.Once);
 		}
 
 		[Fact]
 		public void ReactWithClientOnlyTrueShouldCallRenderHtmlWithTrue()
 		{
 			var component = new Mock<IReactComponent>();
-			component.Setup(x => x.RenderHtml(true, true)).Returns("HTML");
+			component.Setup(x => x.RenderHtml(true, true, null)).Returns("HTML");
 			var environment = ConfigureMockEnvironment();
 			environment.Setup(x => x.CreateComponent(
 				"ComponentName",
@@ -100,13 +100,13 @@ public void ReactWithClientOnlyTrueShouldCallRenderHtmlWithTrue()
 				clientOnly: true,
 				serverOnly: true
 			);
-			component.Verify(x => x.RenderHtml(It.Is<bool>(y => y == true), It.Is<bool>(z => z == true)), Times.Once);
+			component.Verify(x => x.RenderHtml(It.Is<bool>(y => y == true), It.Is<bool>(z => z == true), null), Times.Once);
 		}
 
 		[Fact]
 		public void ReactWithServerOnlyTrueShouldCallRenderHtmlWithTrue() {
 			var component = new Mock<IReactComponent>();
-			component.Setup(x => x.RenderHtml(true, true)).Returns("HTML");
+			component.Setup(x => x.RenderHtml(true, true, null)).Returns("HTML");
 			var environment = ConfigureMockEnvironment();
 			environment.Setup(x => x.CreateComponent(
 				"ComponentName",
@@ -123,7 +123,7 @@ public void ReactWithServerOnlyTrueShouldCallRenderHtmlWithTrue() {
 				clientOnly: true,
 				serverOnly: true
 			);
-			component.Verify(x => x.RenderHtml(It.Is<bool>(y => y == true), It.Is<bool>(z => z == true)), Times.Once);
+			component.Verify(x => x.RenderHtml(It.Is<bool>(y => y == true), It.Is<bool>(z => z == true), null), Times.Once);
 		}
 	}
 }