Problem Details Override Option

samples/MiddlewareSample/MiddlewareSample.Api/Program.cs

@@ -15,12 +15,19 @@
 
 // Register custom exceptions and status codes
 builder.Services
-    // .AddExceptionsMiddleware() -> Use this extension for  default correlation key/value
+    // .AddExceptionsMiddleware() -> Use this extension for  default correlation key/value and configuration
     .AddExceptionsMiddleware(options =>
     {
         options.CorrelationKey = "X-TestCorrelation-Id";
         options.CorrelationKey = CORRELATION_HEADER_KEY;
         options.ConfigureCorrelationValue = (httpContext) => httpContext.TraceIdentifier;
+
+        options.ConfigureProblemDetails = (httpContext, exception, problemDetails) =>
+        {
+            Console.WriteLine("Here you can override the ProblemDetails object returned to the client.");
+            Console.WriteLine("Also a good place to breakpoint during development to examine thrown exceptions.");
+            return problemDetails;
+        };
     }) // Use this extension for  default correlation key/value
         .AddException<RandomException>(HttpStatusCode.FailedDependency);
 

src/Middleware/src/ApplicationBuilder/ApplicationBuilderMiddleware.cs

@@ -160,6 +160,11 @@ async Task LogAndWriteProblemDetailsExceptionAsync(ProblemDetails problemDetails
 
             httpContext.Response.StatusCode = problemDetails.Status ?? (int)HttpStatusCode.InternalServerError;
 
+            if (exceptionsMiddlewareOptionsValue.ConfigureProblemDetails is not null)
+            {
+                problemDetails = exceptionsMiddlewareOptionsValue.ConfigureProblemDetails(httpContext, exception, problemDetails);
+            }
+
             await httpContext.Response.WriteAsJsonAsync(
                 problemDetails,
                 problemDetails.GetType(), // WriteAsJson needs type to add additional fields provided in ValidationProblemDetails

src/Middleware/src/ExceptionsMiddlewareOptions.cs

@@ -4,6 +4,7 @@
 // -------------------------------------------------------
 
 using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
 using System.Net;
 
 namespace BlazorFocused.Exceptions.Middleware;
@@ -32,4 +33,9 @@ public class ExceptionsMiddlewareOptions
     /// Default error status code if none specified for given type of exception
     /// </summary>
     public HttpStatusCode DefaultErrorStatusCode { get; set; } = HttpStatusCode.InternalServerError;
+
+    /// <summary>
+    /// Provide a way to override/configure the ProblemDetails object before it is returned to the client
+    /// </summary>
+    public Func<HttpContext, Exception, ProblemDetails, ProblemDetails> ConfigureProblemDetails { get; set; }
 }

src/Middleware/test/ApplicationBuilder/ApplicationBuilderMiddlewareTests.ProblemDetail.cs

@@ -3,6 +3,8 @@
 // Licensed under the MIT License
 // -------------------------------------------------------
 
+using BlazorFocused.Exceptions.Middleware.ApplicationBuilder;
+using BlazorFocused.Exceptions.Middleware.ExceptionBuilder;
 using Bogus;
 using FluentAssertions;
 using Microsoft.AspNetCore.Http;
@@ -11,8 +13,6 @@
 using Microsoft.Extensions.Options;
 using Moq;
 using System.Net;
-using BlazorFocused.Exceptions.Middleware.ApplicationBuilder;
-using BlazorFocused.Exceptions.Middleware.ExceptionBuilder;
 
 namespace BlazorFocused.Exceptions.Middleware.Test.ApplicationBuilder;
 
@@ -30,7 +30,7 @@ public async Task Invoke_ShouldReturnProblemDetailsNoConfiguration(Exception thr
 
         requestDelegateMock.Setup(request =>
                 request.Invoke(httpContext))
-                    .ThrowsAsync(thrownException);
+            .ThrowsAsync(thrownException);
 
         Exception actualException =
             await Record.ExceptionAsync(() =>
@@ -54,7 +54,8 @@ await Record.ExceptionAsync(() =>
 
     [Theory]
     [MemberData(nameof(ExceptionsWithStatusCode))]
-    public async Task Invoke_ShouldReturnProblemDetailsWithDefaultMessage(Exception thrownException, HttpStatusCode expectedStatusCode)
+    public async Task Invoke_ShouldReturnProblemDetailsWithDefaultMessage(Exception thrownException,
+        HttpStatusCode expectedStatusCode)
     {
         using MemoryStream memoryStream =
             GenerateHttpContext(out string expectedInstance, out HttpContext httpContext);
@@ -73,7 +74,7 @@ public async Task Invoke_ShouldReturnProblemDetailsWithDefaultMessage(Exception
 
         requestDelegateMock.Setup(request =>
                 request.Invoke(httpContext))
-                    .ThrowsAsync(thrownException);
+            .ThrowsAsync(thrownException);
 
         Exception actualException =
             await Record.ExceptionAsync(() =>
@@ -125,7 +126,7 @@ public async Task Invoke_ShouldReturnProblemDetailsWithConfiguredMessage()
 
         requestDelegateMock.Setup(request =>
                 request.Invoke(httpContext))
-                    .ThrowsAsync(thrownException);
+            .ThrowsAsync(thrownException);
 
         Exception actualException =
             await Record.ExceptionAsync(() =>
@@ -147,4 +148,58 @@ await Record.ExceptionAsync(() =>
         Assert.Equal((int)expectedStatusCode, httpContext.Response.StatusCode);
         Assert.Equal(thrownException.GetType().Name, actualErrorResponse.Type);
     }
+
+    [Fact]
+    public async Task Invoke_ShouldAllowProblemDetailsOverride()
+    {
+        string exceptionMessage = new Faker().Lorem.Sentence();
+        string expectedType = "Test Override 1";
+        string overrideInstance = " - Test Override 2";
+        string overrideMessage = "Test Override 3 ";
+        string expectedDetail = overrideMessage + exceptionMessage;
+        int expectedStatusCode = (int)HttpStatusCode.GatewayTimeout;
+        var thrownException = new ApplicationException(exceptionMessage);
+
+        using MemoryStream memoryStream =
+            GenerateHttpContext(out string initialInstance, out HttpContext httpContext);
+
+        string expectedInstance = initialInstance + overrideInstance;
+
+        IOptionsMonitor<ExceptionsMiddlewareBuilderOptions> optionsMonitor = null;
+        var exceptionsMiddlewareOptions = new ExceptionsMiddlewareOptions
+        {
+            ConfigureProblemDetails = (httpContext, exceptionMessage, problemDetails) =>
+            {
+                problemDetails.Detail = overrideMessage + exceptionMessage.Message;
+                problemDetails.Instance = httpContext.Request.Path + httpContext.Request.QueryString + overrideInstance;
+                problemDetails.Status = expectedStatusCode;
+                problemDetails.Type = expectedType;
+
+                return problemDetails;
+            }
+        };
+
+        requestDelegateMock.Setup(request =>
+                request.Invoke(httpContext))
+            .ThrowsAsync(thrownException);
+
+        Exception actualException =
+            await Record.ExceptionAsync(() =>
+                applicationBuilderMiddleware.Invoke(
+                    httpContext,
+                    Options.Create(exceptionsMiddlewareOptions),
+                    optionsMonitor,
+                    NullLogger<ApplicationBuilderMiddleware>.Instance));
+
+        ProblemDetails actualErrorResponse = await GetErrorResponseFromBody<ProblemDetails>(memoryStream);
+
+        // Should be null since error is caught
+        actualException.Should().BeNull();
+
+        Assert.Equal(expectedDetail, actualErrorResponse.Detail);
+        Assert.Equal(expectedInstance, actualErrorResponse.Instance);
+        Assert.Equal(expectedStatusCode, actualErrorResponse.Status);
+        Assert.Equal(expectedType, actualErrorResponse.Type);
+        Assert.NotEqual(expectedStatusCode, httpContext.Response.StatusCode);
+    }
 }