Implemented support for multiple Produces for the same status code

Co-authored-by: captainsafia <1857993+captainsafia@users.noreply.github.com>

Author: Copilot

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

@@ -13,6 +13,11 @@ namespace Microsoft.AspNetCore.Mvc.ApiExplorer;
 
 internal sealed class ApiResponseTypeProvider
 {
+    internal readonly record struct ResponseKey(
+        int StatusCode,
+        Type? DeclaredType,
+        string? ContentType);
+
     private readonly IModelMetadataProvider _modelMetadataProvider;
     private readonly IActionResultTypeMapper _mapper;
     private readonly MvcOptions _mvcOptions;
@@ -87,9 +92,7 @@ private ICollection<ApiResponseType> GetApiResponseTypes(
             responseTypeMetadataProviders,
             _modelMetadataProvider);
 
-        // Read response metadata from providers and
-        // overwrite responseTypes from the metadata based
-        // on the status code
+        // Read response metadata from providers
         var responseTypesFromProvider = ReadResponseMetadata(
             responseMetadataAttributes,
             type,
@@ -98,6 +101,7 @@ private ICollection<ApiResponseType> GetApiResponseTypes(
             out var _,
             responseTypeMetadataProviders);
 
+        // Merge the response types
         foreach (var responseType in responseTypesFromProvider)
         {
             responseTypes[responseType.Key] = responseType.Value;
@@ -106,7 +110,11 @@ private ICollection<ApiResponseType> GetApiResponseTypes(
         // Set the default status only when no status has already been set explicitly
         if (responseTypes.Count == 0 && type != null)
         {
-            responseTypes.Add(StatusCodes.Status200OK, new ApiResponseType
+            var key = new ResponseKey(
+                StatusCodes.Status200OK,
+                type,
+                null);
+            responseTypes.Add(key, new ApiResponseType
             {
                 StatusCode = StatusCodes.Status200OK,
                 Type = type,
@@ -128,11 +136,16 @@ private ICollection<ApiResponseType> GetApiResponseTypes(
             CalculateResponseFormatForType(apiResponse, contentTypes, responseTypeMetadataProviders, _modelMetadataProvider);
         }
 
-        return responseTypes.Values;
+        // Order the response types by status code, type name, and content type for consistent output
+        return responseTypes.Values
+            .OrderBy(r => r.StatusCode)
+            .ThenBy(r => r.Type?.Name)
+            .ThenBy(r => r.ApiResponseFormats.FirstOrDefault()?.MediaType)
+            .ToList();
     }
 
     // Shared with EndpointMetadataApiDescriptionProvider
-    internal static Dictionary<int, ApiResponseType> ReadResponseMetadata(
+    internal static Dictionary<ResponseKey, ApiResponseType> ReadResponseMetadata(
         IReadOnlyList<IApiResponseMetadataProvider> responseMetadataAttributes,
         Type? type,
         Type? defaultErrorType,
@@ -142,7 +155,7 @@ internal static Dictionary<int, ApiResponseType> ReadResponseMetadata(
         IModelMetadataProvider? modelMetadataProvider = null)
     {
         errorSetByDefault = false;
-        var results = new Dictionary<int, ApiResponseType>();
+        var results = new Dictionary<ResponseKey, ApiResponseType>();
 
         // Get the content type that the action explicitly set to support.
         // Walk through all 'filter' attributes in order, and allow each one to see or override
@@ -213,21 +226,27 @@ internal static Dictionary<int, ApiResponseType> ReadResponseMetadata(
 
                 if (apiResponseType.Type != null)
                 {
-                    results[apiResponseType.StatusCode] = apiResponseType;
+                    var mediaType = apiResponseType.ApiResponseFormats.FirstOrDefault()?.MediaType;
+                    var key = new ResponseKey(
+                        apiResponseType.StatusCode,
+                        apiResponseType.Type,
+                        mediaType);
+                    
+                    results[key] = apiResponseType;
                 }
             }
         }
 
         return results;
     }
 
-    internal static Dictionary<int, ApiResponseType> ReadResponseMetadata(
+    internal static Dictionary<ResponseKey, ApiResponseType> ReadResponseMetadata(
         IReadOnlyList<IProducesResponseTypeMetadata> responseMetadata,
         Type? type,
         IEnumerable<IApiResponseTypeMetadataProvider>? responseTypeMetadataProviders = null,
         IModelMetadataProvider? modelMetadataProvider = null)
     {
-        var results = new Dictionary<int, ApiResponseType>();
+        var results = new Dictionary<ResponseKey, ApiResponseType>();
 
         foreach (var metadata in responseMetadata)
         {
@@ -269,7 +288,12 @@ internal static Dictionary<int, ApiResponseType> ReadResponseMetadata(
 
             if (apiResponseType.Type != null)
             {
-                results[apiResponseType.StatusCode] = apiResponseType;
+                var mediaType = apiResponseType.ApiResponseFormats.FirstOrDefault()?.MediaType;
+                var key = new ResponseKey(
+                    apiResponseType.StatusCode,
+                    apiResponseType.Type,
+                    mediaType);
+                results[key] = apiResponseType;
             }
         }
 

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

@@ -346,7 +346,12 @@ private static void AddSupportedResponseTypes(
 
         // We favor types added via the extension methods (which implements IProducesResponseTypeMetadata)
         // over those that are added via attributes.
-        var responseMetadataTypes = producesResponseMetadataTypes.Values.Concat(responseProviderMetadataTypes.Values);
+        // Order the combined list of response types by status code for consistent output
+        var responseMetadataTypes = producesResponseMetadataTypes.Values
+            .Concat(responseProviderMetadataTypes.Values)
+            .OrderBy(r => r.StatusCode)
+            .ThenBy(r => r.Type?.Name)
+            .ThenBy(r => r.ApiResponseFormats.FirstOrDefault()?.MediaType);
 
         if (responseMetadataTypes.Any())
         {

src/Mvc/Mvc.ApiExplorer/test/ApiResponseTypeProviderTest.cs

@@ -823,6 +823,40 @@ public void GetApiResponseTypes_ReturnNoResponseTypes_IfActionWithIResultReturnT
         // Assert
         Assert.False(result.Any());
     }
+    
+    [Fact]
+    public void GetApiResponseTypes_HandlesMultipleResponseTypesWithSameStatusCodeButDifferentContentTypes()
+    {
+        // Arrange
+        var actionDescriptor = GetControllerActionDescriptor(typeof(TestController), nameof(TestController.GetUser));
+        actionDescriptor.FilterDescriptors.Add(new FilterDescriptor(new ProducesResponseTypeAttribute(typeof(BaseModel), 200, "application/json"), FilterScope.Action));
+        actionDescriptor.FilterDescriptors.Add(new FilterDescriptor(new ProducesResponseTypeAttribute(typeof(string), 200, "text/html"), FilterScope.Action));
+        
+        var provider = GetProvider();
+
+        // Act
+        var result = provider.GetApiResponseTypes(actionDescriptor);
+
+        // Assert
+        Assert.Equal(2, result.Count);
+        
+        var orderedResults = result.OrderBy(r => r.ApiResponseFormats.FirstOrDefault()?.MediaType).ToList();
+        
+        Assert.Collection(
+            orderedResults,
+            responseType =>
+            {
+                Assert.Equal(typeof(BaseModel), responseType.Type);
+                Assert.Equal(200, responseType.StatusCode);
+                Assert.Equal(new[] { "application/json" }, GetSortedMediaTypes(responseType));
+            },
+            responseType =>
+            {
+                Assert.Equal(typeof(string), responseType.Type);
+                Assert.Equal(200, responseType.StatusCode);
+                Assert.Equal(new[] { "text/html" }, GetSortedMediaTypes(responseType));
+            });
+    }
 
     private static ApiResponseTypeProvider GetProvider()
     {