Dispose components on client disconnects (#6693)

* Dispose components on client disconnects
Fixes https://github.com/aspnet/AspNetCore/issues/4047

src/Components/.editorconfig

@@ -25,3 +25,31 @@ indent_size = 2
 
 [*.{xml,csproj,config,*proj,targets,props}]
 indent_size = 2
+
+# Dotnet code style settings:
+[*.cs]
+# Sort using and Import directives with System.* appearing first
+dotnet_sort_system_directives_first = true
+
+# Don't use this. qualifier
+dotnet_style_qualification_for_field = false:suggestion
+dotnet_style_qualification_for_property = false:suggestion
+
+# use int x = .. over Int32
+dotnet_style_predefined_type_for_locals_parameters_members = true:suggestion
+
+# use int.MaxValue over Int32.MaxValue
+dotnet_style_predefined_type_for_member_access = true:suggestion
+
+# Require var all the time.
+csharp_style_var_for_built_in_types = true:suggestion
+csharp_style_var_when_type_is_apparent = true:suggestion
+csharp_style_var_elsewhere = true:suggestion
+
+# Newline settings
+csharp_new_line_before_open_brace = all
+csharp_new_line_before_else = true
+csharp_new_line_before_catch = true
+csharp_new_line_before_finally = true
+csharp_new_line_before_members_in_object_initializers = true
+csharp_new_line_before_members_in_anonymous_types = true

src/Components/blazor/src/Microsoft.AspNetCore.Blazor/Rendering/WebAssemblyRenderer.cs

@@ -15,7 +15,7 @@ namespace Microsoft.AspNetCore.Blazor.Rendering
     /// Provides mechanisms for rendering <see cref="IComponent"/> instances in a
     /// web browser, dispatching events to them, and refreshing the UI as required.
     /// </summary>
-    public class WebAssemblyRenderer : Renderer, IDisposable
+    public class WebAssemblyRenderer : Renderer
     {
         private readonly int _webAssemblyRendererId;
 
@@ -71,11 +71,10 @@ namespace Microsoft.AspNetCore.Blazor.Rendering
             RenderRootComponent(componentId);
         }
 
-        /// <summary>
-        /// Disposes the instance.
-        /// </summary>
-        public void Dispose()
+        /// <inheritdoc />
+        protected override void Dispose(bool disposing)
         {
+            base.Dispose(disposing);
             RendererRegistry.Current.TryRemove(_webAssemblyRendererId);
         }
 

src/Components/src/Microsoft.AspNetCore.Components.Browser/Properties/AssemblyInfo.cs

@@ -2,3 +2,5 @@ using System.Runtime.CompilerServices;
 
 [assembly: InternalsVisibleTo("Microsoft.AspNetCore.Blazor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.AspNetCore.Components.Server, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+
+[assembly: InternalsVisibleTo("Microsoft.AspNetCore.Components.Server.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]

src/Components/src/Microsoft.AspNetCore.Components.Server/Circuits/CircuitHost.cs

@@ -16,7 +16,7 @@ namespace Microsoft.AspNetCore.Components.Server.Circuits
 {
     internal class CircuitHost : IDisposable
     {
-        private static AsyncLocal<CircuitHost> _current = new AsyncLocal<CircuitHost>();
+        private static readonly AsyncLocal<CircuitHost> _current = new AsyncLocal<CircuitHost>();
 
         /// <summary>
         /// Gets the current <see cref="Circuit"/>, if any.
@@ -24,23 +24,18 @@ namespace Microsoft.AspNetCore.Components.Server.Circuits
         public static CircuitHost Current => _current.Value;
 
         /// <summary>
-        /// Sets the current <see cref="Circuit"/>.
+        /// Sets the current <see cref="Circuits.Circuit"/>.
         /// </summary>
-        /// <param name="circuitHost">The <see cref="Circuit"/>.</param>
+        /// <param name="circuitHost">The <see cref="Circuits.Circuit"/>.</param>
         /// <remarks>
         /// Calling <see cref="SetCurrentCircuitHost(CircuitHost)"/> will store the circuit
         /// and other related values such as the <see cref="IJSRuntime"/> and <see cref="Renderer"/>
         /// in the local execution context. Application code should not need to call this method,
-        /// it is primarily used by the Server-Side Blazor infrastructure.
+        /// it is primarily used by the Server-Side Components infrastructure.
         /// </remarks>
         public static void SetCurrentCircuitHost(CircuitHost circuitHost)
         {
-            if (circuitHost == null)
-            {
-                throw new ArgumentNullException(nameof(circuitHost));
-            }
-
-            _current.Value = circuitHost;
+            _current.Value = circuitHost ?? throw new ArgumentNullException(nameof(circuitHost));
 
             Microsoft.JSInterop.JSRuntime.SetCurrentJSRuntime(circuitHost.JSRuntime);
             RendererRegistry.SetCurrentRendererRegistry(circuitHost.RendererRegistry);
@@ -134,6 +129,7 @@ namespace Microsoft.AspNetCore.Components.Server.Circuits
         public void Dispose()
         {
             Scope.Dispose();
+            Renderer.Dispose();
         }
 
         private void AssertInitialized()

src/Components/src/Microsoft.AspNetCore.Components.Server/Circuits/RemoteRenderer.cs

@@ -120,11 +120,10 @@ namespace Microsoft.AspNetCore.Components.Browser.Rendering
             }
         }
 
-        /// <summary>
-        /// Disposes the instance.
-        /// </summary>
-        public void Dispose()
+        /// <inheritdoc />
+        protected override void Dispose(bool disposing)
         {
+            base.Dispose(true);
             _rendererRegistry.TryRemove(_id);
         }
 

src/Components/src/Microsoft.AspNetCore.Components/Rendering/Renderer.cs

@@ -12,19 +12,17 @@ namespace Microsoft.AspNetCore.Components.Rendering
     /// Provides mechanisms for rendering hierarchies of <see cref="IComponent"/> instances,
     /// dispatching events to them, and notifying when the user interface is being updated.
     /// </summary>
-    public abstract class Renderer
+    public abstract class Renderer : IDisposable
     {
         private readonly ComponentFactory _componentFactory;
-        private int _nextComponentId = 0; // TODO: change to 'long' when Mono .NET->JS interop supports it
-        private readonly Dictionary<int, ComponentState> _componentStateById
-            = new Dictionary<int, ComponentState>();
-
+        private readonly Dictionary<int, ComponentState> _componentStateById = new Dictionary<int, ComponentState>();
         private readonly RenderBatchBuilder _batchBuilder = new RenderBatchBuilder();
-        private bool _isBatchInProgress;
-
-        private int _lastEventHandlerId = 0;
         private readonly Dictionary<int, EventHandlerInvoker> _eventBindings = new Dictionary<int, EventHandlerInvoker>();
 
+        private int _nextComponentId = 0; // TODO: change to 'long' when Mono .NET->JS interop supports it
+        private bool _isBatchInProgress;
+        private int _lastEventHandlerId = 0;
+
         /// <summary>
         /// Constructs an instance of <see cref="Renderer"/>.
         /// </summary>
@@ -175,7 +173,7 @@ namespace Microsoft.AspNetCore.Components.Rendering
 
             if (frame.AttributeValue is MulticastDelegate @delegate)
             {
-               _eventBindings.Add(id, new EventHandlerInvoker(@delegate));
+                _eventBindings.Add(id, new EventHandlerInvoker(@delegate));
             }
 
             frame = frame.WithAttributeEventHandlerId(id);
@@ -295,5 +293,44 @@ namespace Microsoft.AspNetCore.Components.Rendering
                     RemoveEventHandlerIds(eventHandlerIdsClone, Task.CompletedTask));
             }
         }
+
+        /// <summary>
+        /// Releases all resources currently used by this <see cref="Renderer"/> instance.
+        /// </summary>
+        /// <param name="disposing"><see langword="true"/> if this method is being invoked by <see cref="IDisposable.Dispose"/>, otherwise <see langword="false"/>.</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            List<Exception> exceptions = null;
+
+            foreach (var componentState in _componentStateById.Values)
+            {
+                if (componentState.Component is IDisposable disposable)
+                {
+                    try
+                    {
+                        disposable.Dispose();
+                    }
+                    catch (Exception exception)
+                    {
+                        // Capture exceptions thrown by individual components and rethrow as an aggregate.
+                        exceptions = exceptions ?? new List<Exception>();
+                        exceptions.Add(exception);
+                    }
+                }
+            }
+
+            if (exceptions != null)
+            {
+                throw new AggregateException(exceptions);
+            }
+        }
+
+        /// <summary>
+        /// Releases all resources currently used by this <see cref="Renderer"/> instance.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(disposing: true);
+        }
     }
 }

src/Components/test/Microsoft.AspNetCore.Components.Server.Test/Circuits/CircuitHostTest.cs

@@ -0,0 +1,61 @@
+// 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 System;
+using System.Threading;
+using Microsoft.AspNetCore.Components.Browser;
+using Microsoft.AspNetCore.Components.Browser.Rendering;
+using Microsoft.AspNetCore.SignalR;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.JSInterop;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Components.Server.Circuits
+{
+    public class CircuitHostTest
+    {
+        [Fact]
+        public void Dispose_DisposesResources()
+        {
+            // Arrange
+            var serviceScope = new Mock<IServiceScope>();
+            var clientProxy = Mock.Of<IClientProxy>();
+            var renderRegistry = new RendererRegistry();
+            var jsRuntime = Mock.Of<IJSRuntime>();
+            var syncContext = new CircuitSynchronizationContext();
+
+            var remoteRenderer = new TestRemoteRenderer(
+                Mock.Of<IServiceProvider>(),
+                renderRegistry,
+                jsRuntime,
+                clientProxy,
+                syncContext);
+
+            var circuitHost = new CircuitHost(serviceScope.Object, clientProxy, renderRegistry, remoteRenderer, configure: _ => { }, jsRuntime: jsRuntime, synchronizationContext: syncContext);
+
+            // Act
+            circuitHost.Dispose();
+
+            // Assert
+            serviceScope.Verify(s => s.Dispose(), Times.Once());
+            Assert.True(remoteRenderer.Disposed);
+        }
+
+        private class TestRemoteRenderer : RemoteRenderer
+        {
+            public TestRemoteRenderer(IServiceProvider serviceProvider, RendererRegistry rendererRegistry, IJSRuntime jsRuntime, IClientProxy client, SynchronizationContext syncContext)
+                : base(serviceProvider, rendererRegistry, jsRuntime, client, syncContext)
+            {
+            }
+
+            public bool Disposed { get; set; }
+
+            protected override void Dispose(bool disposing)
+            {
+                base.Dispose(disposing);
+                Disposed = true;
+            }
+        }
+    }
+}

src/Components/test/Microsoft.AspNetCore.Components.Server.Test/Microsoft.AspNetCore.Components.Server.Test.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.0</TargetFramework>
@@ -7,6 +7,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
+    <PackageReference Include="Moq" Version="4.10.0" />
     <PackageReference Include="xunit" Version="2.3.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
   </ItemGroup>

src/Components/test/Microsoft.AspNetCore.Components.Test/RendererTest.cs

@@ -5,7 +5,6 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Components;
 using Microsoft.AspNetCore.Components.Rendering;
 using Microsoft.AspNetCore.Components.RenderTree;
 using Microsoft.AspNetCore.Components.Test.Helpers;
@@ -1139,6 +1138,78 @@ namespace Microsoft.AspNetCore.Components.Test
             Assert.Equal(2, numEventsFired);
         }
 
+        [Fact]
+        public void DisposingRenderer_DisposesTopLevelComponents()
+        {
+            // Arrange
+            var renderer = new TestRenderer();
+            var component = new DisposableComponent();
+            renderer.AssignRootComponentId(component);
+
+            // Act
+            renderer.Dispose();
+
+            // Assert
+            Assert.True(component.Disposed);
+        }
+
+        [Fact]
+        public void DisposingRenderer_DisposesNestedComponents()
+        {
+            // Arrange
+            var renderer = new TestRenderer();
+            var component = new TestComponent(builder =>
+            {
+                builder.AddContent(0, "Hello");
+                builder.OpenComponent<DisposableComponent>(1);
+                builder.CloseComponent();
+            });
+            var componentId = renderer.AssignRootComponentId(component);
+            component.TriggerRender();
+            var batch = renderer.Batches.Single();
+            var componentFrame = batch.ReferenceFrames
+                .Single(frame => frame.FrameType == RenderTreeFrameType.Component);
+            var nestedComponent = Assert.IsType<DisposableComponent>(componentFrame.Component);
+
+            // Act
+            renderer.Dispose();
+
+            // Assert
+            Assert.True(component.Disposed);
+            Assert.True(nestedComponent.Disposed);
+        }
+
+        [Fact]
+        public void DisposingRenderer_CapturesExceptionsFromAllRegisteredComponents()
+        {
+            // Arrange
+            var renderer = new TestRenderer();
+            var exception1 = new Exception();
+            var exception2 = new Exception();
+            var component = new TestComponent(builder =>
+            {
+                builder.AddContent(0, "Hello");
+                builder.OpenComponent<DisposableComponent>(1);
+                builder.AddAttribute(1, nameof(DisposableComponent.DisposeAction), (Action)(() => throw exception1));
+                builder.CloseComponent();
+
+                builder.OpenComponent<DisposableComponent>(2);
+                builder.AddAttribute(1, nameof(DisposableComponent.DisposeAction), (Action)(() => throw exception2));
+                builder.CloseComponent();
+            });
+            var componentId = renderer.AssignRootComponentId(component);
+            component.TriggerRender();
+
+            // Act &A Assert
+            var aggregate = Assert.Throws<AggregateException>(renderer.Dispose);
+
+            // All components must be disposed even if some throw as part of being diposed.
+            Assert.True(component.Disposed);
+            Assert.Equal(2, aggregate.InnerExceptions.Count);
+            Assert.Contains(exception1, aggregate.InnerExceptions);
+            Assert.Contains(exception2, aggregate.InnerExceptions);
+        }
+
         private class NoOpRenderer : Renderer
         {
             public NoOpRenderer() : base(new TestServiceProvider())
@@ -1152,7 +1223,7 @@ namespace Microsoft.AspNetCore.Components.Test
                 => Task.CompletedTask;
         }
 
-        private class TestComponent : IComponent
+        private class TestComponent : IComponent, IDisposable
         {
             private RenderHandle _renderHandle;
             private RenderFragment _renderFragment;
@@ -1172,6 +1243,10 @@ namespace Microsoft.AspNetCore.Components.Test
 
             public void TriggerRender()
                 => _renderHandle.Render(_renderFragment);
+
+            public bool Disposed { get; private set; }
+
+            void IDisposable.Dispose() => Disposed = true;
         }
 
         private class MessageComponent : AutoRenderComponent
@@ -1398,6 +1473,24 @@ namespace Microsoft.AspNetCore.Components.Test
             }
         }
 
+        private class DisposableComponent : AutoRenderComponent, IDisposable
+        {
+            public bool Disposed { get; private set; }
+
+            [Parameter]
+            public Action DisposeAction { get; private set; }
+
+            public void Dispose()
+            {
+                Disposed = true;
+                DisposeAction?.Invoke();
+            }
+
+            protected override void BuildRenderTree(RenderTreeBuilder builder)
+            {
+            }
+        }
+
         class TestAsyncRenderer : TestRenderer
         {
             public Task NextUpdateDisplayReturnTask { get; set; }