Add 'default response' to API Response Type

Also some cleanup and unit tests.

src/Microsoft.AspNetCore.Mvc.Abstractions/ApiExplorer/ApiResponseType.cs

@@ -39,5 +39,15 @@ namespace Microsoft.AspNetCore.Mvc.ApiExplorer
         /// Gets or sets the HTTP response status code.
         /// </summary>
         public int StatusCode { get; set; }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether the response type represents a default response.
+        /// </summary>
+        /// <remarks>
+        /// If an <see cref="ApiDescription"/> has a default response, then the <see cref="StatusCode"/> property should be ignored. This response
+        /// will be used when a more specific response format does not apply. The common use of a default response is to specify the format
+        /// for communicating error conditions.
+        /// </remarks>
+        public bool IsDefaultResponse { get; set; }
     }
 }

src/Microsoft.AspNetCore.Mvc.ApiExplorer/ApiBehaviorApiDescriptionProvider.cs

@@ -0,0 +1,116 @@
+// 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.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc.Abstractions;
+using Microsoft.AspNetCore.Mvc.Internal;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+
+namespace Microsoft.AspNetCore.Mvc.ApiExplorer
+{
+    public class ApiBehaviorApiDescriptionProvider : IApiDescriptionProvider
+    {
+        private readonly IModelMetadataProvider _modelMetadaProvider;
+
+        public ApiBehaviorApiDescriptionProvider(IModelMetadataProvider modelMetadataProvider)
+        {
+            _modelMetadaProvider = modelMetadataProvider;
+        }
+
+        /// <remarks>
+        /// The order is set to execute after the default provider.
+        /// </remarks>
+        public int Order => -1000 + 10;
+
+        public void OnProvidersExecuted(ApiDescriptionProviderContext context)
+        {
+        }
+
+        public void OnProvidersExecuting(ApiDescriptionProviderContext context)
+        {
+            foreach (var description in context.Results)
+            {
+                if (!AppliesTo(description))
+                {
+                    continue;
+                }
+
+                foreach (var responseType in CreateProblemResponseTypes(description))
+                {
+                    description.SupportedResponseTypes.Add(responseType);
+                }
+            }
+        }
+
+        public bool AppliesTo(ApiDescription description)
+        {
+            return description.ActionDescriptor.FilterDescriptors.Any(f => f.Filter is IApiBehaviorMetadata);
+        }
+
+        // Check if the parameter is named "id" (e.g. int id) or ends in Id (e.g. personId)
+        public bool IsIdParameter(ParameterDescriptor parameter)
+        {
+            if (parameter.Name == null)
+            {
+                return false;
+            }
+
+            if (string.Equals("id", parameter.Name, StringComparison.Ordinal))
+            {
+                return true;
+            }
+
+            // We're looking for a name ending with Id, but preceded by a lower case letter. This should match
+            // the normal PascalCase naming conventions.
+            if (parameter.Name.Length >= 3 && 
+                parameter.Name.EndsWith("Id", StringComparison.Ordinal) && 
+                char.IsLower(parameter.Name, parameter.Name.Length - 3))
+            {
+                return true;
+            }
+
+            return false;
+        }
+
+        public IEnumerable<ApiResponseType> CreateProblemResponseTypes(ApiDescription description)
+        {
+            if (description.ActionDescriptor.Parameters.Any() || description.ActionDescriptor.BoundProperties.Any())
+            {
+                // For validation errors.
+                yield return CreateProblemResponse(StatusCodes.Status400BadRequest);
+
+                if (description.ActionDescriptor.Parameters.Any(p => IsIdParameter(p)))
+                {
+                    yield return CreateProblemResponse(StatusCodes.Status404NotFound);
+                }
+            }
+
+            yield return CreateProblemResponse(statusCode: 0, isDefaultResponse: true);
+        }
+        
+        private ApiResponseType CreateProblemResponse(int statusCode, bool isDefaultResponse = false)
+        {
+            return new ApiResponseType
+            {
+                ApiResponseFormats = new List<ApiResponseFormat>
+                {
+                    new ApiResponseFormat
+                    {
+                        MediaType = "application/problem+json",
+                    },
+                    new ApiResponseFormat
+                    {
+                        MediaType = "application/problem+xml",
+                    },
+                },
+                IsDefaultResponse = isDefaultResponse,
+                ModelMetadata = _modelMetadaProvider.GetMetadataForType(typeof(ProblemDetails)),
+                StatusCode = statusCode,
+                Type = typeof(ProblemDetails),
+            };
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.ApiExplorer/ApiControllerApiDescriptionProvider.cs

@@ -1,78 +0,0 @@
-// 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.Collections.Generic;
-using System.Linq;
-using Microsoft.AspNetCore.Http;
-using Microsoft.AspNetCore.Mvc.Internal;
-using Microsoft.AspNetCore.Mvc.ModelBinding;
-
-namespace Microsoft.AspNetCore.Mvc.ApiExplorer
-{
-    public class ApiControllerApiDescriptionProvider : IApiDescriptionProvider
-    {
-        private readonly IModelMetadataProvider _modelMetadaProvider;
-
-        public ApiControllerApiDescriptionProvider(IModelMetadataProvider modelMetadataProvider)
-        {
-            _modelMetadaProvider = modelMetadataProvider;
-        }
-
-        /// <remarks>
-        /// The order is set to execute after the <see cref="DefaultApiDescriptionProvider"/>.
-        /// </remarks>
-        public int Order => -1000 + 10;
-
-        public void OnProvidersExecuted(ApiDescriptionProviderContext context)
-        {
-        }
-
-        public void OnProvidersExecuting(ApiDescriptionProviderContext context)
-        {
-            foreach (var apiDescription in context.Results)
-            {
-                if (!apiDescription.ActionDescriptor.FilterDescriptors.Any(f => f.Filter is IApiBehaviorMetadata))
-                {
-                    continue;
-                }
-
-                var parameters = apiDescription.ActionDescriptor.Parameters.Concat(apiDescription.ActionDescriptor.BoundProperties);
-                if (parameters.Any())
-                {
-                    apiDescription.SupportedResponseTypes.Add(CreateProblemResponse(StatusCodes.Status400BadRequest));
-
-                    if (parameters.Any(p => p.Name.EndsWith("id", StringComparison.OrdinalIgnoreCase)))
-                    {
-                        apiDescription.SupportedResponseTypes.Add(CreateProblemResponse(StatusCodes.Status404NotFound));
-                    }
-                }
-
-                // We don't have a good way to signal a "default" response type. We'll use 0 to indicate this until we come up
-                // with something better.
-                apiDescription.SupportedResponseTypes.Add(CreateProblemResponse(statusCode: 0));
-            }
-        }
-
-        private ApiResponseType CreateProblemResponse(int statusCode)
-        {
-            return new ApiResponseType
-            {
-                ApiResponseFormats = new List<ApiResponseFormat>
-                    {
-                        new ApiResponseFormat
-                        {
-                            MediaType = "application/problem+json",
-                        },
-                        new ApiResponseFormat
-                        {
-                            MediaType = "application/problem+xml",
-                        },
-                    },
-                ModelMetadata = _modelMetadaProvider.GetMetadataForType(typeof(ProblemDetails)),
-                StatusCode = statusCode,
-                Type = typeof(ProblemDetails),
-            };
-        }
-    }
-}

src/Microsoft.AspNetCore.Mvc.ApiExplorer/DependencyInjection/MvcApiExplorerMvcCoreBuilderExtensions.cs

@@ -27,7 +27,7 @@ namespace Microsoft.Extensions.DependencyInjection
             services.TryAddEnumerable(
                 ServiceDescriptor.Transient<IApiDescriptionProvider, DefaultApiDescriptionProvider>());
             services.TryAddEnumerable(
-                ServiceDescriptor.Transient<IApiDescriptionProvider, ApiControllerApiDescriptionProvider>());
+                ServiceDescriptor.Transient<IApiDescriptionProvider, ApiBehaviorApiDescriptionProvider>());
         }
     }
 }

src/Microsoft.AspNetCore.Mvc.Core/DependencyInjection/MvcCoreServiceCollectionExtensions.cs

@@ -160,7 +160,7 @@ namespace Microsoft.Extensions.DependencyInjection
             services.TryAddEnumerable(
                 ServiceDescriptor.Transient<IApplicationModelProvider, DefaultApplicationModelProvider>());
             services.TryAddEnumerable(
-                ServiceDescriptor.Transient<IApplicationModelProvider, ApiControllerApplicationModelProvider>());
+                ServiceDescriptor.Transient<IApplicationModelProvider, ApiBehaviorApplicationModelProvider>());
             services.TryAddEnumerable(
                 ServiceDescriptor.Transient<IActionDescriptorProvider, ControllerActionDescriptorProvider>());
 

src/Microsoft.AspNetCore.Mvc.Core/Internal/ApiBehaviorApplicationModelProvider.cs

@@ -12,12 +12,12 @@ using Microsoft.Extensions.Options;
 
 namespace Microsoft.AspNetCore.Mvc.Internal
 {
-    public class ApiControllerApplicationModelProvider : IApplicationModelProvider
+    public class ApiBehaviorApplicationModelProvider : IApplicationModelProvider
     {
         private readonly ApiBehaviorOptions _apiBehaviorOptions;
         private readonly ModelStateInvalidFilter _modelStateInvalidFilter;
 
-        public ApiControllerApplicationModelProvider(IOptions<ApiBehaviorOptions> apiBehaviorOptions, ILoggerFactory loggerFactory)
+        public ApiBehaviorApplicationModelProvider(IOptions<ApiBehaviorOptions> apiBehaviorOptions, ILoggerFactory loggerFactory)
         {
             _apiBehaviorOptions = apiBehaviorOptions.Value;
             if (_apiBehaviorOptions.EnableModelStateInvalidFilter && _apiBehaviorOptions.InvalidModelStateResponseFactory == null)

test/Microsoft.AspNetCore.Mvc.ApiExplorer.Test/ApiBehaviorApiDescriptionProviderTest.cs

@@ -0,0 +1,241 @@
+// 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.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNetCore.Mvc.Abstractions;
+using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.AspNetCore.Mvc.Internal;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.ApiExplorer
+{
+    public class ApiBehaviorApiDescriptionProviderTest
+    {
+        [Fact]
+        public void AppliesTo_ActionWithoutApiBehavior_ReturnsFalse()
+        {
+            // Arrange
+            var action = new ActionDescriptor()
+            {
+                FilterDescriptors = new List<FilterDescriptor>(),
+            };
+            var description = new ApiDescription()
+            {
+                ActionDescriptor = action,
+            };
+
+            var provider = new ApiBehaviorApiDescriptionProvider(new EmptyModelMetadataProvider());
+
+            // Act
+            var result = provider.AppliesTo(description);
+
+            // Assert
+            Assert.False(result);
+        }
+
+        [Fact]
+        public void AppliesTo_ActionWithApiBehavior_ReturnsTrue()
+        {
+            // Arrange
+            var action = new ActionDescriptor()
+            {
+                FilterDescriptors = new List<FilterDescriptor>()
+                {
+                    new FilterDescriptor(Mock.Of<IApiBehaviorMetadata>(), FilterScope.Global),
+                }
+            };
+            var description = new ApiDescription()
+            {
+                ActionDescriptor = action,
+            };
+
+            var provider = new ApiBehaviorApiDescriptionProvider(new EmptyModelMetadataProvider());
+
+            // Act
+            var result = provider.AppliesTo(description);
+
+            // Assert
+            Assert.True(result);
+        }
+
+        [Theory]
+        [InlineData("id")]
+        [InlineData("personId")]
+        [InlineData("üId")]
+        public void IsIdParameter_ParameterNameMatchesConvention_ReturnsTrue(string name)
+        {
+            var parameter = new ParameterDescriptor()
+            {
+                Name = name,
+            };
+
+            var provider = new ApiBehaviorApiDescriptionProvider(new EmptyModelMetadataProvider());
+
+            // Act
+            var result = provider.IsIdParameter(parameter);
+
+            // Assert
+            Assert.True(result);
+        }
+
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        [InlineData("i")]
+        [InlineData("Id")]
+        [InlineData("iD")]
+        [InlineData("persoNId")]
+        [InlineData("personid")]
+        [InlineData("ü Id")]
+        [InlineData("ÜId")]
+        public void IsIdParameter_ParameterNameDoesNotMatchConvention_ReturnsFalse(string name)
+        {
+            var parameter = new ParameterDescriptor()
+            {
+                Name = name,
+            };
+
+            var provider = new ApiBehaviorApiDescriptionProvider(new EmptyModelMetadataProvider());
+
+            // Act
+            var result = provider.IsIdParameter(parameter);
+
+            // Assert
+            Assert.False(result);
+        }
+
+        [Fact]
+        public void CreateProblemResponseTypes_NoParameters_IncludesDefaultResponse()
+        {
+            // Arrange
+            var action = new ActionDescriptor()
+            {
+                FilterDescriptors = new List<FilterDescriptor>()
+                {
+                    new FilterDescriptor(Mock.Of<IApiBehaviorMetadata>(), FilterScope.Global),
+                },
+                BoundProperties = new List<ParameterDescriptor>(),
+                Parameters = new List<ParameterDescriptor>(),
+            };
+            var description = new ApiDescription()
+            {
+                ActionDescriptor = action,
+            };
+
+            var provider = new ApiBehaviorApiDescriptionProvider(new EmptyModelMetadataProvider());
+
+            // Act
+            var results = provider.CreateProblemResponseTypes(description);
+
+            // Assert
+            Assert.Collection(
+                results.OrderBy(r => r.StatusCode),
+                r =>
+                {
+                    Assert.Equal(typeof(ProblemDetails), r.Type);
+                    Assert.Equal(0, r.StatusCode);
+                    Assert.True(r.IsDefaultResponse);
+                });
+        }
+
+        [Fact]
+        public void CreateProblemResponseTypes_WithBoundProperty_Includes400Response()
+        {
+            // Arrange
+            var action = new ActionDescriptor()
+            {
+                FilterDescriptors = new List<FilterDescriptor>()
+                {
+                    new FilterDescriptor(Mock.Of<IApiBehaviorMetadata>(), FilterScope.Global),
+                },
+                BoundProperties = new List<ParameterDescriptor>()
+                {
+                    new ParameterDescriptor()
+                },
+                Parameters = new List<ParameterDescriptor>(),
+            };
+            var description = new ApiDescription()
+            {
+                ActionDescriptor = action,
+            };
+
+            var provider = new ApiBehaviorApiDescriptionProvider(new EmptyModelMetadataProvider());
+
+            // Act
+            var results = provider.CreateProblemResponseTypes(description);
+
+            // Assert
+            Assert.Collection(
+                results.OrderBy(r => r.StatusCode),
+                r =>
+                {
+                    Assert.Equal(typeof(ProblemDetails), r.Type);
+                    Assert.Equal(0, r.StatusCode);
+                    Assert.True(r.IsDefaultResponse);
+                },
+                r =>
+                {
+                    Assert.Equal(typeof(ProblemDetails), r.Type);
+                    Assert.Equal(400, r.StatusCode);
+                    Assert.False(r.IsDefaultResponse);
+                });
+        }
+
+        [Fact]
+        public void CreateProblemResponseTypes_WithIdParameter_Includes404Response()
+        {
+            // Arrange
+            var action = new ActionDescriptor()
+            {
+                FilterDescriptors = new List<FilterDescriptor>()
+                {
+                    new FilterDescriptor(Mock.Of<IApiBehaviorMetadata>(), FilterScope.Global),
+                },
+                BoundProperties = new List<ParameterDescriptor>()
+                {
+                },
+                Parameters = new List<ParameterDescriptor>()
+                {
+                    new ParameterDescriptor()
+                    {
+                        Name = "customerId",
+                    }
+                },
+            };
+            var description = new ApiDescription()
+            {
+                ActionDescriptor = action,
+            };
+
+            var provider = new ApiBehaviorApiDescriptionProvider(new EmptyModelMetadataProvider());
+
+            // Act
+            var results = provider.CreateProblemResponseTypes(description);
+
+            // Assert
+            Assert.Collection(
+                results.OrderBy(r => r.StatusCode),
+                r =>
+                {
+                    Assert.Equal(typeof(ProblemDetails), r.Type);
+                    Assert.Equal(0, r.StatusCode);
+                    Assert.True(r.IsDefaultResponse);
+                },
+                r =>
+                {
+                    Assert.Equal(typeof(ProblemDetails), r.Type);
+                    Assert.Equal(400, r.StatusCode);
+                    Assert.False(r.IsDefaultResponse);
+                },
+                r =>
+                {
+                    Assert.Equal(typeof(ProblemDetails), r.Type);
+                    Assert.Equal(404, r.StatusCode);
+                    Assert.False(r.IsDefaultResponse);
+                });
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/DependencyInjection/MvcCoreServiceCollectionExtensionsTest.cs

@@ -295,7 +295,7 @@ namespace Microsoft.AspNetCore.Mvc
                         new Type[]
                         {
                             typeof(DefaultApplicationModelProvider),
-                            typeof(ApiControllerApplicationModelProvider),
+                            typeof(ApiBehaviorApplicationModelProvider),
                         }
                     },
                 };

test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/ApiBehaviorApplicationModelProviderTest.cs

@@ -11,7 +11,7 @@ using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc.Internal
 {
-    public class ApiControllerApplicationModelProviderTest
+    public class ApiBehaviorApplicationModelProviderTest
     {
         [Fact]
         public void OnProvidersExecuting_AddsModelStateInvalidFilter_IfTypeIsAnnotatedWithAttribute()
@@ -23,7 +23,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 InvalidModelStateResponseFactory = _ => null,
             });
 
-            var provider = new ApiControllerApplicationModelProvider(options, NullLoggerFactory.Instance);
+            var provider = new ApiBehaviorApplicationModelProvider(options, NullLoggerFactory.Instance);
 
             // Act
             provider.OnProvidersExecuting(context);
@@ -43,7 +43,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 EnableModelStateInvalidFilter = false,
             });
 
-            var provider = new ApiControllerApplicationModelProvider(options, NullLoggerFactory.Instance);
+            var provider = new ApiBehaviorApplicationModelProvider(options, NullLoggerFactory.Instance);
 
             // Act
             provider.OnProvidersExecuting(context);
@@ -63,7 +63,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 InvalidModelStateResponseFactory = _ => null,
             });
 
-            var provider = new ApiControllerApplicationModelProvider(options, NullLoggerFactory.Instance);
+            var provider = new ApiBehaviorApplicationModelProvider(options, NullLoggerFactory.Instance);
 
             // Act
             provider.OnProvidersExecuting(context);
@@ -91,7 +91,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 EnableModelStateInvalidFilter = false,
             });
 
-            var provider = new ApiControllerApplicationModelProvider(options, NullLoggerFactory.Instance);
+            var provider = new ApiBehaviorApplicationModelProvider(options, NullLoggerFactory.Instance);
 
             // Act
             provider.OnProvidersExecuting(context);
@@ -119,7 +119,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
                 InvalidModelStateResponseFactory = _ => null,
             });
 
-            var provider = new ApiControllerApplicationModelProvider(options, NullLoggerFactory.Instance);
+            var provider = new ApiBehaviorApplicationModelProvider(options, NullLoggerFactory.Instance);
 
             // Act & Assert
             var ex = Assert.Throws<InvalidOperationException>(() => provider.OnProvidersExecuting(context));

test/Microsoft.AspNetCore.Mvc.FunctionalTests/ApiExplorerTest.cs

@@ -1079,6 +1079,7 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
                 response =>
                 {
                     Assert.Equal(0, response.StatusCode);
+                    Assert.True(response.IsDefaultResponse);
                     AssertProblemDetails(response);
                 });
         }
@@ -1097,12 +1098,14 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
                 response =>
                 {
                     Assert.Equal(0, response.StatusCode);
+                    Assert.True(response.IsDefaultResponse);
                     AssertProblemDetails(response);
                 },
                 response => Assert.Equal(200, response.StatusCode),
                 response =>
                 {
                     Assert.Equal(400, response.StatusCode);
+                    Assert.False(response.IsDefaultResponse);
                     AssertProblemDetails(response);
                 });
         }
@@ -1123,17 +1126,20 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
                 response =>
                 {
                     Assert.Equal(0, response.StatusCode);
+                    Assert.True(response.IsDefaultResponse);
                     AssertProblemDetails(response);
                 },
                 response => Assert.Equal(200, response.StatusCode),
                 response =>
                 {
                     Assert.Equal(400, response.StatusCode);
+                    Assert.False(response.IsDefaultResponse);
                     AssertProblemDetails(response);
                 },
                 response =>
                 {
                     Assert.Equal(404, response.StatusCode);
+                    Assert.False(response.IsDefaultResponse);
                     AssertProblemDetails(response);
                 });
         }
@@ -1199,6 +1205,8 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             public string ResponseType { get; set; }
 
             public int StatusCode { get; set; }
+
+            public bool IsDefaultResponse { get; set; }
         }
 
         private class ApiExplorerResponseFormat

test/Microsoft.AspNetCore.Mvc.Test/MvcServiceCollectionExtensionsTest.cs

@@ -417,7 +417,7 @@ namespace Microsoft.AspNetCore.Mvc
                             typeof(CorsApplicationModelProvider),
                             typeof(AuthorizationApplicationModelProvider),
                             typeof(TempDataApplicationModelProvider),
-                            typeof(ApiControllerApplicationModelProvider),
+                            typeof(ApiBehaviorApplicationModelProvider),
                         }
                     },
                     {
@@ -425,7 +425,7 @@ namespace Microsoft.AspNetCore.Mvc
                         new Type[]
                         {
                             typeof(DefaultApiDescriptionProvider),
-                            typeof(ApiControllerApiDescriptionProvider),
+                            typeof(ApiBehaviorApiDescriptionProvider),
                             typeof(JsonPatchOperationsArrayProvider),
                         }
                     },

test/WebSites/ApiExplorerWebSite/ApiExplorerDataFilter.cs

@@ -89,7 +89,8 @@ namespace ApiExplorerWebSite
                 var responseType = new ApiExplorerResponseType()
                 {
                     StatusCode = response.StatusCode,
-                    ResponseType = response.Type?.FullName
+                    ResponseType = response.Type?.FullName,
+                    IsDefaultResponse = response.IsDefaultResponse,
                 };
 
                 foreach(var responseFormat in response.ApiResponseFormats)
@@ -152,6 +153,8 @@ namespace ApiExplorerWebSite
             public string ResponseType { get; set; }
 
             public int StatusCode { get; set; }
+
+            public bool IsDefaultResponse { get; set; }
         }
 
         private class ApiExplorerResponseFormat