Add support for stating accepts/consumes metadata is required or not

src/Http/Http.Abstractions/src/Metadata/IAcceptsMetadata.cs

@@ -21,5 +21,10 @@ public interface IAcceptsMetadata
         /// Gets the type being read from the request. 
         /// </summary>
         Type? RequestType { get; }
+
+        /// <summary>
+        /// Gets a value that determines if the request body is optional.
+        /// </summary>
+        bool IsOptional { get; }
     }
 }

src/Http/Http.Abstractions/src/PublicAPI.Unshipped.txt

@@ -10,6 +10,7 @@ Microsoft.AspNetCore.Http.IResult
 Microsoft.AspNetCore.Http.IResult.ExecuteAsync(Microsoft.AspNetCore.Http.HttpContext! httpContext) -> System.Threading.Tasks.Task!
 Microsoft.AspNetCore.Http.Metadata.IAcceptsMetadata
 Microsoft.AspNetCore.Http.Metadata.IAcceptsMetadata.ContentTypes.get -> System.Collections.Generic.IReadOnlyList<string!>!
+Microsoft.AspNetCore.Http.Metadata.IAcceptsMetadata.IsOptional.get -> bool
 Microsoft.AspNetCore.Http.Metadata.IAcceptsMetadata.RequestType.get -> System.Type?
 Microsoft.AspNetCore.Http.Metadata.IFromBodyMetadata
 Microsoft.AspNetCore.Http.Metadata.IFromBodyMetadata.AllowEmpty.get -> bool

src/Http/Http.Extensions/src/RequestDelegateFactory.cs

@@ -62,8 +62,7 @@ public static partial class RequestDelegateFactory
         private static ParameterExpression TempSourceStringExpr => TryParseMethodCache.TempSourceStringExpr;
         private static readonly BinaryExpression TempSourceStringNotNullExpr = Expression.NotEqual(TempSourceStringExpr, Expression.Constant(null));
         private static readonly BinaryExpression TempSourceStringNullExpr = Expression.Equal(TempSourceStringExpr, Expression.Constant(null));
-
-        private static readonly AcceptsMetadata DefaultAcceptsMetadata = new(new[] { "application/json" });
+        private static readonly string[] DefaultAcceptsContentType = new[] { "application/json" };
 
         /// <summary>
         /// Creates a <see cref="RequestDelegate"/> implementation for <paramref name="handler"/>.
@@ -879,11 +878,11 @@ private static Expression BindParameterFromBody(ParameterInfo parameter, bool al
                 }
             }
 
-            factoryContext.Metadata.Add(DefaultAcceptsMetadata);
             var isOptional = IsOptionalParameter(parameter, factoryContext);
 
             factoryContext.JsonRequestBodyType = parameter.ParameterType;
             factoryContext.AllowEmptyRequestBody = allowEmpty || isOptional;
+            factoryContext.Metadata.Add(new AcceptsMetadata(parameter.ParameterType, factoryContext.AllowEmptyRequestBody, DefaultAcceptsContentType));
 
             if (!factoryContext.AllowEmptyRequestBody)
             {

src/Http/Routing/test/UnitTests/Builder/DelegateEndpointRouteBuilderExtensionsTest.cs

@@ -290,14 +290,13 @@ public void MapPost_BuildsEndpointWithCorrectEndpointMetadata()
             // Trigger Endpoint build by calling getter.
             var endpoint = Assert.Single(dataSource.Endpoints);
 
-            var endpointMetadata = endpoint.Metadata.GetOrderedMetadata<IAcceptsMetadata>();
+            var endpointMetadata = endpoint.Metadata.GetMetadata<IAcceptsMetadata>();
+
             Assert.NotNull(endpointMetadata);
-            Assert.Equal(2, endpointMetadata.Count);
+            Assert.False(endpointMetadata!.IsOptional);
+            Assert.Equal(typeof(Todo), endpointMetadata.RequestType);
+            Assert.Equal(new[] { "application/xml" }, endpointMetadata.ContentTypes);
 
-            var lastAddedMetadata = endpointMetadata[^1];
-
-            Assert.Equal(typeof(Todo), lastAddedMetadata.RequestType);
-            Assert.Equal(new[] { "application/xml" }, lastAddedMetadata.ContentTypes);
         }
 
         [Fact]
@@ -567,13 +566,13 @@ public TestConsumesAttribute(Type requestType, string contentType, params string
             }
 
             IReadOnlyList<string> IAcceptsMetadata.ContentTypes => _contentTypes;
-
             Type? IAcceptsMetadata.RequestType => _requestType;
 
+            bool IAcceptsMetadata.IsOptional => false;
+
             Type? _requestType;
 
             List<string> _contentTypes = new();
-
         }
 
         class Todo

src/Mvc/Mvc.ApiExplorer/src/EndpointMetadataApiDescriptionProvider.cs

@@ -102,8 +102,6 @@ private ApiDescription CreateApiDescription(RouteEndpoint routeEndpoint, string
                 },
             };
 
-            var hasJsonBody = false;
-
             foreach (var parameter in methodInfo.GetParameters())
             {
                 var parameterDescription = CreateApiParameterDescription(parameter, routeEndpoint.RoutePattern);
@@ -113,33 +111,37 @@ private ApiDescription CreateApiDescription(RouteEndpoint routeEndpoint, string
                     continue;
                 }
 
-                if (parameterDescription.Source == BindingSource.Body)
-                {
-                    hasJsonBody = true;
-                }
-
                 apiDescription.ParameterDescriptions.Add(parameterDescription);
             }
 
-            // Get custom attributes for the handler. ConsumesAttribute is one of the examples.
-            var acceptsRequestType = routeEndpoint.Metadata.GetMetadata<IAcceptsMetadata>()?.RequestType;
-            if (acceptsRequestType is not null)
+            // Get IAcceptsMetadata.
+            var acceptsMetadata = routeEndpoint.Metadata.GetMetadata<IAcceptsMetadata>();
+            if (acceptsMetadata is not null)
             {
+                var acceptsRequestType = acceptsMetadata.RequestType;
+                var isOptional = acceptsMetadata.IsOptional;
                 var parameterDescription = new ApiParameterDescription
                 {
-                    Name = acceptsRequestType.Name,
-                    ModelMetadata = CreateModelMetadata(acceptsRequestType),
+                    Name = acceptsRequestType is not null ? acceptsRequestType.Name : typeof(void).Name,
+                    ModelMetadata = CreateModelMetadata(acceptsRequestType ?? typeof(void)),
                     Source = BindingSource.Body,
-                    Type = acceptsRequestType,
-                    IsRequired = true,
+                    Type = acceptsRequestType ?? typeof(void),
+                    IsRequired = !isOptional,
                 };
-
                 apiDescription.ParameterDescriptions.Add(parameterDescription);
+
+                var supportedRequestFormats = apiDescription.SupportedRequestFormats;
+
+                foreach (var contentType in acceptsMetadata.ContentTypes)
+                {
+                    supportedRequestFormats.Add(new ApiRequestFormat
+                    {
+                        MediaType = contentType
+                    });
+                }
             }
 
-            AddSupportedRequestFormats(apiDescription.SupportedRequestFormats, hasJsonBody, routeEndpoint.Metadata);
             AddSupportedResponseTypes(apiDescription.SupportedResponseTypes, methodInfo.ReturnType, routeEndpoint.Metadata);
-
             AddActionDescriptorEndpointMetadata(apiDescription.ActionDescriptor, routeEndpoint.Metadata);
 
             return apiDescription;
@@ -150,7 +152,8 @@ private ApiDescription CreateApiDescription(RouteEndpoint routeEndpoint, string
             var (source, name, allowEmpty) = GetBindingSourceAndName(parameter, pattern);
 
             // Services are ignored because they are not request parameters.
-            if (source == BindingSource.Services)
+            // We ignore/skip body parameter because the value will be retrieved from the IAcceptsMetadata.
+            if (source == BindingSource.Services || source == BindingSource.Body)
             {
                 return null;
             }
@@ -222,33 +225,6 @@ private ApiDescription CreateApiDescription(RouteEndpoint routeEndpoint, string
             }
         }
 
-        private static void AddSupportedRequestFormats(
-            IList<ApiRequestFormat> supportedRequestFormats,
-            bool hasJsonBody,
-            EndpointMetadataCollection endpointMetadata)
-        {
-            var requestMetadata = endpointMetadata.GetOrderedMetadata<IApiRequestMetadataProvider>();
-            var declaredContentTypes = DefaultApiDescriptionProvider.GetDeclaredContentTypes(requestMetadata);
-
-            if (declaredContentTypes.Count > 0)
-            {
-                foreach (var contentType in declaredContentTypes)
-                {
-                    supportedRequestFormats.Add(new ApiRequestFormat
-                    {
-                        MediaType = contentType,
-                    });
-                }
-            }
-            else if (hasJsonBody)
-            {
-                supportedRequestFormats.Add(new ApiRequestFormat
-                {
-                    MediaType = "application/json",
-                });
-            }
-        }
-
         private static void AddSupportedResponseTypes(
             IList<ApiResponseType> supportedResponseTypes,
             Type returnType,