IExceptionHandler for exception handler middleware #46280 (#47923)

src/Middleware/Diagnostics/src/ExceptionHandler/ExceptionHandlerExtensions.cs

@@ -97,6 +97,7 @@ private static IApplicationBuilder SetExceptionHandlerMiddleware(IApplicationBui
             {
                 var loggerFactory = app.ApplicationServices.GetRequiredService<ILoggerFactory>();
                 var diagnosticListener = app.ApplicationServices.GetRequiredService<DiagnosticListener>();
+                var exceptionHandlers = app.ApplicationServices.GetRequiredService<IEnumerable<IExceptionHandler>>();
 
                 if (options is null)
                 {
@@ -110,7 +111,7 @@ private static IApplicationBuilder SetExceptionHandlerMiddleware(IApplicationBui
                     options.Value.ExceptionHandler = newNext;
                 }
 
-                return new ExceptionHandlerMiddlewareImpl(next, loggerFactory, options, diagnosticListener, problemDetailsService).Invoke;
+                return new ExceptionHandlerMiddlewareImpl(next, loggerFactory, options, diagnosticListener, exceptionHandlers, problemDetailsService).Invoke;
             });
         }
 

src/Middleware/Diagnostics/src/ExceptionHandler/ExceptionHandlerMiddleware.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
+using System.Linq;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
@@ -29,11 +30,12 @@ public class ExceptionHandlerMiddleware
         IOptions<ExceptionHandlerOptions> options,
         DiagnosticListener diagnosticListener)
     {
-        _innerMiddlewareImpl = new (
+        _innerMiddlewareImpl = new(
             next,
             loggerFactory,
             options,
             diagnosticListener,
+            Enumerable.Empty<IExceptionHandler>(),
             problemDetailsService: null);
     }
 

src/Middleware/Diagnostics/src/ExceptionHandler/ExceptionHandlerMiddlewareImpl.cs

@@ -16,7 +16,7 @@ namespace Microsoft.AspNetCore.Diagnostics;
 /// <summary>
 /// A middleware for handling exceptions in the application.
 /// </summary>
-internal class ExceptionHandlerMiddlewareImpl
+internal sealed class ExceptionHandlerMiddlewareImpl
 {
     private const int DefaultStatusCode = StatusCodes.Status500InternalServerError;
 
@@ -25,6 +25,7 @@ internal class ExceptionHandlerMiddlewareImpl
     private readonly ILogger _logger;
     private readonly Func<object, Task> _clearCacheHeadersDelegate;
     private readonly DiagnosticListener _diagnosticListener;
+    private readonly IExceptionHandler[] _exceptionHandlers;
     private readonly IProblemDetailsService? _problemDetailsService;
 
     /// <summary>
@@ -34,19 +35,22 @@ internal class ExceptionHandlerMiddlewareImpl
     /// <param name="loggerFactory">The <see cref="ILoggerFactory"/> used for logging.</param>
     /// <param name="options">The options for configuring the middleware.</param>
     /// <param name="diagnosticListener">The <see cref="DiagnosticListener"/> used for writing diagnostic messages.</param>
+    /// <param name="exceptionHandlers"></param>
     /// <param name="problemDetailsService">The <see cref="IProblemDetailsService"/> used for writing <see cref="ProblemDetails"/> messages.</param>
     public ExceptionHandlerMiddlewareImpl(
         RequestDelegate next,
         ILoggerFactory loggerFactory,
         IOptions<ExceptionHandlerOptions> options,
         DiagnosticListener diagnosticListener,
+        IEnumerable<IExceptionHandler> exceptionHandlers,
         IProblemDetailsService? problemDetailsService = null)
     {
         _next = next;
         _options = options.Value;
         _logger = loggerFactory.CreateLogger<ExceptionHandlerMiddleware>();
         _clearCacheHeadersDelegate = ClearCacheHeaders;
         _diagnosticListener = diagnosticListener;
+        _exceptionHandlers = exceptionHandlers as IExceptionHandler[] ?? new List<IExceptionHandler>(exceptionHandlers).ToArray();
         _problemDetailsService = problemDetailsService;
 
         if (_options.ExceptionHandler == null)
@@ -133,7 +137,7 @@ private async Task HandleException(HttpContext context, ExceptionDispatchInfo ed
             edi.Throw();
         }
 
-        PathString originalPath = context.Request.Path;
+        var originalPath = context.Request.Path;
         if (_options.ExceptionHandlingPath.HasValue)
         {
             context.Request.Path = _options.ExceptionHandlingPath;
@@ -155,24 +159,35 @@ private async Task HandleException(HttpContext context, ExceptionDispatchInfo ed
             context.Response.StatusCode = DefaultStatusCode;
             context.Response.OnStarting(_clearCacheHeadersDelegate, context.Response);
 
-            var problemDetailsWritten = false;
-            if (_options.ExceptionHandler != null)
+            var handled = false;
+            foreach (var exceptionHandler in _exceptionHandlers)
             {
-                await _options.ExceptionHandler!(context);
+                handled = await exceptionHandler.TryHandleAsync(context, edi.SourceException, context.RequestAborted);
+                if (handled)
+                {
+                    break;
+                }
             }
-            else
+
+            if (!handled)
             {
-                problemDetailsWritten = await _problemDetailsService!.TryWriteAsync(new()
+                if (_options.ExceptionHandler is not null)
                 {
-                    HttpContext = context,
-                    AdditionalMetadata = exceptionHandlerFeature.Endpoint?.Metadata,
-                    ProblemDetails = { Status = DefaultStatusCode },
-                    Exception = edi.SourceException,
-                });
+                    await _options.ExceptionHandler!(context);
+                }
+                else
+                {
+                    handled = await _problemDetailsService!.TryWriteAsync(new()
+                    {
+                        HttpContext = context,
+                        AdditionalMetadata = exceptionHandlerFeature.Endpoint?.Metadata,
+                        ProblemDetails = { Status = DefaultStatusCode },
+                        Exception = edi.SourceException,
+                    });
+                }
             }
-
             // If the response has already started, assume exception handler was successful.
-            if (context.Response.HasStarted || problemDetailsWritten || context.Response.StatusCode != StatusCodes.Status404NotFound || _options.AllowStatusCode404Response)
+            if (context.Response.HasStarted || handled || context.Response.StatusCode != StatusCodes.Status404NotFound || _options.AllowStatusCode404Response)
             {
                 const string eventName = "Microsoft.AspNetCore.Diagnostics.HandledException";
                 if (_diagnosticListener.IsEnabled() && _diagnosticListener.IsEnabled(eventName))

src/Middleware/Diagnostics/src/ExceptionHandler/ExceptionHandlerServiceCollectionExtensions.cs

@@ -1,7 +1,9 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Diagnostics;
 
 namespace Microsoft.Extensions.DependencyInjection;
 
@@ -38,4 +40,16 @@ public static IServiceCollection AddExceptionHandler(this IServiceCollection ser
         services.AddOptions<ExceptionHandlerOptions>().Configure(configureOptions);
         return services;
     }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    /// <param name="services"></param>
+    /// <returns></returns>
+
+    public static IServiceCollection AddExceptionHandler<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] T>(this IServiceCollection services) where T : class, IExceptionHandler
+    {
+        return services.AddSingleton<IExceptionHandler, T>();
+    }
 }

src/Middleware/Diagnostics/src/ExceptionHandler/IExceptionHandler.cs

@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.AspNetCore.Http;
+
+namespace Microsoft.AspNetCore.Diagnostics;
+
+/// <summary>
+/// 
+/// </summary>
+public interface IExceptionHandler
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="httpContext"></param>
+    /// <param name="exception"></param>
+    /// <param name="cancellationToken"></param>
+    /// <returns></returns>
+    ValueTask<bool> TryHandleAsync(HttpContext httpContext, Exception exception, CancellationToken cancellationToken);
+}

src/Middleware/Diagnostics/src/PublicAPI.Unshipped.txt

@@ -1,2 +1,5 @@
 #nullable enable
+Microsoft.AspNetCore.Diagnostics.IExceptionHandler
+Microsoft.AspNetCore.Diagnostics.IExceptionHandler.TryHandleAsync(Microsoft.AspNetCore.Http.HttpContext! httpContext, System.Exception! exception, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.ValueTask<bool>
 Microsoft.AspNetCore.Diagnostics.StatusCodeReExecuteFeature.OriginalStatusCode.get -> int
+static Microsoft.Extensions.DependencyInjection.ExceptionHandlerServiceCollectionExtensions.AddExceptionHandler<T>(this Microsoft.Extensions.DependencyInjection.IServiceCollection! services) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!

src/Middleware/Diagnostics/test/UnitTests/ExceptionHandlerMiddlewareTest.cs

@@ -114,6 +114,105 @@ public async Task Invoke_ExceptionHandlerCaptureRouteValuesAndEndpoint()
         await middleware.Invoke(httpContext);
     }
 
+    [Fact]
+    public async Task IExceptionHandlers_CallNextIfNotHandled()
+    {
+        // Arrange
+        var httpContext = CreateHttpContext();
+
+        var optionsAccessor = CreateOptionsAccessor();
+
+        var exceptionHandlers = new List<IExceptionHandler>
+        {
+            new TestExceptionHandler(false, "1"),
+            new TestExceptionHandler(false, "2"),
+            new TestExceptionHandler(true, "3"),
+        };
+
+        var middleware = CreateMiddleware(_ => throw new InvalidOperationException(), optionsAccessor, exceptionHandlers);
+
+        // Act & Assert
+        await middleware.Invoke(httpContext);
+
+        Assert.True(httpContext.Items.ContainsKey("1"));
+        Assert.True(httpContext.Items.ContainsKey("2"));
+        Assert.True(httpContext.Items.ContainsKey("3"));
+    }
+
+    [Fact]
+    public async Task IExceptionHandlers_SkipIfOneHandle()
+    {
+        // Arrange
+        var httpContext = CreateHttpContext();
+
+        var optionsAccessor = CreateOptionsAccessor();
+
+        var exceptionHandlers = new List<IExceptionHandler>
+        {
+            new TestExceptionHandler(false, "1"),
+            new TestExceptionHandler(true, "2"),
+            new TestExceptionHandler(true, "3"),
+        };
+
+        var middleware = CreateMiddleware(_ => throw new InvalidOperationException(), optionsAccessor, exceptionHandlers);
+
+        // Act & Assert
+        await middleware.Invoke(httpContext);
+
+        Assert.True(httpContext.Items.ContainsKey("1"));
+        Assert.True(httpContext.Items.ContainsKey("2"));
+        Assert.False(httpContext.Items.ContainsKey("3"));
+    }
+
+    [Fact]
+    public async Task IExceptionHandlers_CallOptionExceptionHandlerIfNobodyHandles()
+    {
+        // Arrange
+        var httpContext = CreateHttpContext();
+
+        var optionsAccessor = CreateOptionsAccessor(
+            (context) =>
+            {
+                context.Items["ExceptionHandler"] = true;
+                return Task.CompletedTask;
+            });
+
+        var exceptionHandlers = new List<IExceptionHandler>
+        {
+            new TestExceptionHandler(false, "1"),
+            new TestExceptionHandler(false, "2"),
+            new TestExceptionHandler(false, "3"),
+        };
+
+        var middleware = CreateMiddleware(_ => throw new InvalidOperationException(), optionsAccessor, exceptionHandlers);
+
+        // Act & Assert
+        await middleware.Invoke(httpContext);
+
+        Assert.True(httpContext.Items.ContainsKey("1"));
+        Assert.True(httpContext.Items.ContainsKey("2"));
+        Assert.True(httpContext.Items.ContainsKey("3"));
+        Assert.True(httpContext.Items.ContainsKey("ExceptionHandler"));
+    }
+
+    private class TestExceptionHandler : IExceptionHandler
+    {
+        private readonly bool _handle;
+        private readonly string _name;
+
+        public TestExceptionHandler(bool handle, string name)
+        {
+            _handle = handle;
+            _name = name;
+        }
+
+        public ValueTask<bool> TryHandleAsync(HttpContext httpContext, Exception exception, CancellationToken cancellationToken)
+        {
+            httpContext.Items[_name] = true;
+            return ValueTask.FromResult(_handle);
+        }
+    }
+
     private HttpContext CreateHttpContext()
     {
         var httpContext = new DefaultHttpContext
@@ -138,18 +237,20 @@ private HttpContext CreateHttpContext()
         return optionsAccessor;
     }
 
-    private ExceptionHandlerMiddleware CreateMiddleware(
+    private ExceptionHandlerMiddlewareImpl CreateMiddleware(
         RequestDelegate next,
-        IOptions<ExceptionHandlerOptions> options)
+        IOptions<ExceptionHandlerOptions> options,
+        IEnumerable<IExceptionHandler> exceptionHandlers = null)
     {
         next ??= c => Task.CompletedTask;
         var listener = new DiagnosticListener("Microsoft.AspNetCore");
 
-        var middleware = new ExceptionHandlerMiddleware(
+        var middleware = new ExceptionHandlerMiddlewareImpl(
             next,
             NullLoggerFactory.Instance,
             options,
-            listener);
+            listener,
+            exceptionHandlers ?? Enumerable.Empty<IExceptionHandler>());
 
         return middleware;
     }