Add support for setting error type via ProducesResponseType attribute

src/Mvc/Mvc.ApiExplorer/src/ApiResponseTypeProvider.cs

@@ -101,17 +101,21 @@ private ICollection<ApiResponseType> GetApiResponseTypes(
 
                     if (apiResponseType.Type == typeof(void))
                     {
-                        if (type != null && (statusCode == StatusCodes.Status200OK || statusCode == StatusCodes.Status201Created))
+                        var statusOkWithType = type != null && (statusCode == StatusCodes.Status200OK || statusCode == StatusCodes.Status201Created);
+                        var hasDefaultErrorTypeOverride = metadataAttribute is ProducesResponseTypeAttribute producesResponseTypeAttribute && producesResponseTypeAttribute.OverrideDefaultErrorType;
+                        var errorOrDefaultResponse = IsClientError(statusCode) || apiResponseType.IsDefaultResponse;
+                        // ProducesResponseTypeAttribute's constructor defaults to setting "Type" to void when no value is specified.
+                        // In this event, use the action's return type for 200 or 201 status codes. This lets you decorate an action with a
+                        // [ProducesResponseType(201)] instead of [ProducesResponseType(201, typeof(Person)] when typeof(Person) can be inferred
+                        // from the return type.
+                        if (statusOkWithType)
                         {
-                            // ProducesResponseTypeAttribute's constructor defaults to setting "Type" to void when no value is specified.
-                            // In this event, use the action's return type for 200 or 201 status codes. This lets you decorate an action with a
-                            // [ProducesResponseType(201)] instead of [ProducesResponseType(201, typeof(Person)] when typeof(Person) can be inferred
-                            // from the return type.
                             apiResponseType.Type = type;
                         }
-                        else if (IsClientError(statusCode) || apiResponseType.IsDefaultResponse)
+                        // Use the default error type for "default" responses or 4xx client errors if no response type is specified.
+                        // Unless falling back to the default error type is explicitly disabled.
+                        else if (errorOrDefaultResponse && !hasDefaultErrorTypeOverride)
                         {
-                            // Use the default error type for "default" responses or 4xx client errors if no response type is specified.
                             apiResponseType.Type = defaultErrorType;
                         }
                     }

src/Mvc/Mvc.Core/src/ProducesResponseTypeAttribute.cs

@@ -15,7 +15,7 @@ public class ProducesResponseTypeAttribute : Attribute, IApiResponseMetadataProv
     {
         /// <summary>
         /// Initializes an instance of <see cref="ProducesResponseTypeAttribute"/>.
-        /// </summary>       
+        /// </summary>
         /// <param name="statusCode">The HTTP response status code.</param>
         public ProducesResponseTypeAttribute(int statusCode)
             : this(typeof(void), statusCode)
@@ -31,6 +31,18 @@ public ProducesResponseTypeAttribute(Type type, int statusCode)
         {
             Type = type ?? throw new ArgumentNullException(nameof(type));
             StatusCode = statusCode;
+            OverrideDefaultErrorType = false;
+        }
+
+        /// <summary>
+        /// Initializes an instance of <see cref="ProducesResponseTypeAttribute"/>.
+        /// </summary>
+        /// <param name="type">The <see cref="Type"/> of object that is going to be written in the response.</param>
+        /// <param name="statusCode">The HTTP response status code.</param>
+        /// <param name="overrideDefaultErrorType">Whether or not to override default error type</param>
+        public ProducesResponseTypeAttribute(Type type, int statusCode, bool overrideDefaultErrorType) : this(type, statusCode)
+        {
+            OverrideDefaultErrorType = overrideDefaultErrorType;
         }
 
         /// <summary>
@@ -43,6 +55,19 @@ public ProducesResponseTypeAttribute(Type type, int statusCode)
         /// </summary>
         public int StatusCode { get; set; }
 
+        /// <summary>
+        /// Gets or sets whether or not the default error type should be used when one
+        /// is expliclty provided as a type in the <see cref="ProducesResponseTypeAttribute"/>.
+        ///
+        /// When <see langword="true"/>, the ApiExplorer will use the provided <see cref="Type"/>
+        /// as the default type for error objects.
+        ///
+        /// When <see langword="false"/>, the ApiExplorer will use the globally configured default
+        /// error type.
+        /// </summary>
+        /// <value></value>
+        public bool OverrideDefaultErrorType { get; set; }
+
         /// <inheritdoc />
         void IApiResponseMetadataProvider.SetContentTypes(MediaTypeCollection contentTypes)
         {

src/Mvc/Mvc.Core/src/PublicAPI.Unshipped.txt

@@ -849,6 +849,9 @@ Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.ValidationSta
 Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.ValidationVisitor(Microsoft.AspNetCore.Mvc.ActionContext! actionContext, Microsoft.AspNetCore.Mvc.ModelBinding.Validation.IModelValidatorProvider! validatorProvider, Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidatorCache! validatorCache, Microsoft.AspNetCore.Mvc.ModelBinding.IModelMetadataProvider! metadataProvider, Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationStateDictionary? validationState) -> void
 Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.ValidatorProvider.get -> Microsoft.AspNetCore.Mvc.ModelBinding.Validation.IModelValidatorProvider!
 Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidatorCache.GetValidators(Microsoft.AspNetCore.Mvc.ModelBinding.ModelMetadata! metadata, Microsoft.AspNetCore.Mvc.ModelBinding.Validation.IModelValidatorProvider! validatorProvider) -> System.Collections.Generic.IReadOnlyList<Microsoft.AspNetCore.Mvc.ModelBinding.Validation.IModelValidator!>!
+~Microsoft.AspNetCore.Mvc.ProducesResponseTypeAttribute.ProducesResponseTypeAttribute(System.Type type, int statusCode, bool overrideDefaultErrorType) -> void
+Microsoft.AspNetCore.Mvc.ProducesResponseTypeAttribute.OverrideDefaultErrorType.get -> bool
+Microsoft.AspNetCore.Mvc.ProducesResponseTypeAttribute.OverrideDefaultErrorType.set -> void
 Microsoft.AspNetCore.Mvc.Routing.DynamicRouteValueTransformer.State.get -> object?
 Microsoft.AspNetCore.Mvc.Routing.DynamicRouteValueTransformer.State.set -> void
 Microsoft.AspNetCore.Mvc.Routing.HttpMethodAttribute.HttpMethodAttribute(System.Collections.Generic.IEnumerable<string!>! httpMethods) -> void

src/Mvc/test/Mvc.FunctionalTests/ApiExplorerTest.cs

@@ -1461,6 +1461,29 @@ public async Task ApiConvention_ForActionWithApiConventionMethod()
                 });
         }
 
+        [Theory]
+        [InlineData("ActionWithVoidTypeAndOverrideDisabled", typeof(ProblemDetails))]
+        [InlineData("ActionWithVoidType", typeof(void))]
+        public async Task ApiAction_ForActionWithVoidResponseType(string path, Type type)
+        {
+            // Act
+            var response = await Client.GetAsync($"http://localhost/ApiExplorerVoid/{path}");
+
+            var responseBody = await response.EnsureSuccessStatusCode().Content.ReadAsStringAsync();
+            var result = JsonConvert.DeserializeObject<List<ApiExplorerData>>(responseBody);
+
+            // Assert
+            var description = Assert.Single(result);
+            Assert.Collection(
+                description.SupportedResponseTypes.OrderBy(r => r.StatusCode),
+                responseType =>
+                {
+                    Assert.Equal(type.FullName, responseType.ResponseType);
+                    Assert.Equal(401, responseType.StatusCode);
+                    Assert.False(responseType.IsDefaultResponse);
+                });
+        }
+
         private IEnumerable<string> GetSortedMediaTypes(ApiExplorerResponseType apiResponseType)
         {
             return apiResponseType.ResponseFormats

src/Mvc/test/WebSites/ApiExplorerWebSite/Controllers/ApiExplorerSystemVoid.cs

@@ -0,0 +1,19 @@
+// 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 Microsoft.AspNetCore.Mvc;
+
+namespace ApiExplorerWebSite
+{
+    [Route("ApiExplorerVoid/[action]")]
+    [ApiController]
+    public class ApiExplorerVoidController : Controller
+    {
+        [ProducesResponseType(typeof(void), 401, true)]
+        public IActionResult ActionWithVoidType() => Ok();
+
+        [ProducesResponseType(typeof(void), 401)]
+        public IActionResult ActionWithVoidTypeAndOverrideDisabled() => Ok();
+
+    }
+}