Add tests which now succeed

Author: sander1095

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

@@ -375,6 +375,9 @@ private static void AddSupportedResponseTypes(
                     apiResponseType.ApiResponseFormats.Add(defaultResponseFormat);
                 }
 
+                // We set the Description to the first non-null value we find that matches the status code.
+                apiResponseType.Description ??= responseMetadataTypes.FirstOrDefault(x => x.StatusCode == apiResponseType.StatusCode && x.Description is not null)?.Description;
+
                 if (!supportedResponseTypes.Any(existingResponseType => existingResponseType.StatusCode == apiResponseType.StatusCode))
                 {
                     supportedResponseTypes.Add(apiResponseType);

src/Mvc/Mvc.ApiExplorer/test/EndpointMetadataApiDescriptionProviderTest.cs

@@ -300,6 +300,81 @@ public void AddsMultipleResponseFormatsForTypedResults()
         Assert.Empty(badRequestResponseType.ApiResponseFormats);
     }
 
+    [Fact]
+    public void AddsResponseDescription()
+    {
+        const string expectedCreatedDescription = "A new item was created";
+        const string expectedBadRequestDescription = "Validation failed for the request";
+
+        var apiDescription = GetApiDescription(
+    [ProducesResponseType(typeof(TimeSpan), StatusCodes.Status201Created, Description = expectedCreatedDescription)]
+        [ProducesResponseType(StatusCodes.Status400BadRequest, Description = expectedBadRequestDescription)]
+        () => TypedResults.Created("https://example.com", new TimeSpan()));
+
+        Assert.Equal(2, apiDescription.SupportedResponseTypes.Count);
+
+        var createdResponseType = apiDescription.SupportedResponseTypes[0];
+
+        Assert.Equal(201, createdResponseType.StatusCode);
+        Assert.Equal(typeof(TimeSpan), createdResponseType.Type);
+        Assert.Equal(typeof(TimeSpan), createdResponseType.ModelMetadata?.ModelType);
+        Assert.Equal(expectedCreatedDescription, createdResponseType.Description);
+
+        var createdResponseFormat = Assert.Single(createdResponseType.ApiResponseFormats);
+        Assert.Equal("application/json", createdResponseFormat.MediaType);
+
+        var badRequestResponseType = apiDescription.SupportedResponseTypes[1];
+
+        Assert.Equal(400, badRequestResponseType.StatusCode);
+        Assert.Equal(typeof(void), badRequestResponseType.Type);
+        Assert.Equal(typeof(void), badRequestResponseType.ModelMetadata?.ModelType);
+        Assert.Equal(expectedBadRequestDescription, badRequestResponseType.Description);
+    }
+
+    [Fact]
+    public void WithEmptyMethodBody_AddsResponseDescription()
+    {
+        const string expectedCreatedDescription = "A new item was created";
+        const string expectedBadRequestDescription = "Validation failed for the request";
+
+        var apiDescription = GetApiDescription(
+    [ProducesResponseType(typeof(TimeSpan), StatusCodes.Status201Created, Description = expectedCreatedDescription)]
+        [ProducesResponseType(StatusCodes.Status400BadRequest, Description = expectedBadRequestDescription)]
+        () => new InferredJsonClass());
+
+        Assert.Equal(3, apiDescription.SupportedResponseTypes.Count);
+
+        var rdfInferredResponseType = apiDescription.SupportedResponseTypes[0];
+
+        Assert.Equal(200, rdfInferredResponseType.StatusCode);
+        Assert.Equal(typeof(InferredJsonClass), rdfInferredResponseType.Type);
+        Assert.Equal(typeof(InferredJsonClass), rdfInferredResponseType.ModelMetadata?.ModelType);
+
+        var rdfInferredResponseFormat = Assert.Single(rdfInferredResponseType.ApiResponseFormats);
+        Assert.Equal("application/json", rdfInferredResponseFormat.MediaType);
+        Assert.Null(rdfInferredResponseType.Description); // There is no description set for the default "200" code, so we expect it to be null.
+
+        var createdResponseType = apiDescription.SupportedResponseTypes[1];
+
+        Assert.Equal(201, createdResponseType.StatusCode);
+        Assert.Equal(typeof(TimeSpan), createdResponseType.Type);
+        Assert.Equal(typeof(TimeSpan), createdResponseType.ModelMetadata?.ModelType);
+        Assert.Equal(expectedCreatedDescription, createdResponseType.Description);
+
+        var createdResponseFormat = Assert.Single(createdResponseType.ApiResponseFormats);
+        Assert.Equal("application/json", createdResponseFormat.MediaType);
+
+        var badRequestResponseType = apiDescription.SupportedResponseTypes[2];
+
+        Assert.Equal(400, badRequestResponseType.StatusCode);
+        Assert.Equal(typeof(InferredJsonClass), badRequestResponseType.Type);
+        Assert.Equal(typeof(InferredJsonClass), badRequestResponseType.ModelMetadata?.ModelType);
+        Assert.Equal(expectedBadRequestDescription, badRequestResponseType.Description);
+
+        var badRequestResponseFormat = Assert.Single(badRequestResponseType.ApiResponseFormats);
+        Assert.Equal("application/json", badRequestResponseFormat.MediaType);
+    }
+
     [Fact]
     public void AddsResponseFormatsForTypedResultWithoutReturnType()
     {

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Services/OpenApiDocumentService/OpenApiDocumentServiceTests.Responses.cs

@@ -320,7 +320,7 @@ public async Task GetOpenApiResponse_WithEmptyMethodBody_UsesDescriptionSetByUse
         // Act
         builder.MapPost("/api/todos",
             [ProducesResponseType<Todo>(StatusCodes.Status200OK, Description = expectedCreatedDescription)]
-        [ProducesResponseType(StatusCodes.Status400BadRequest)] // Omitted, meaning it should be NULL
+        [ProducesResponseType(StatusCodes.Status400BadRequest, Description = expectedBadRequestDescription)]
         () =>
             { });
 
@@ -354,7 +354,7 @@ public async Task GetOpenApiResponse_UsesDescriptionSetByUser()
         // Act
         builder.MapPost("/api/todos",
             [ProducesResponseType<Todo>(StatusCodes.Status200OK, Description = expectedCreatedDescription)]
-        [ProducesResponseType(StatusCodes.Status400BadRequest)] // Omitted, meaning it should be NULL
+        [ProducesResponseType(StatusCodes.Status400BadRequest, Description = expectedBadRequestDescription)]
         () =>
             { return TypedResults.Ok(new Todo(1, "Lorem", true, DateTime.UtcNow)); }); // This code doesn't return Bad Request, but that doesn't matter for this test.