feat(openapi): support Nullable Description Attribute on enums

src/OpenApi/src/Services/Schemas/OpenApiSchemaService.cs

@@ -100,7 +100,7 @@ internal sealed class OpenApiSchemaService(
             {
                 schema.ApplyNullabilityContextInfo(jsonPropertyInfo);
             }
-            if (context.TypeInfo.Type.GetCustomAttributes(inherit: false).OfType<DescriptionAttribute>().LastOrDefault() is { } typeDescriptionAttribute)
+            if ((context.TypeInfo.ElementType ?? context.TypeInfo.Type).GetCustomAttributes(inherit: false).OfType<DescriptionAttribute>().LastOrDefault() is { } typeDescriptionAttribute)
             {
                 schema[OpenApiSchemaKeywords.DescriptionKeyword] = typeDescriptionAttribute.Description;
             }

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Services/OpenApiSchemaService/OpenApiSchemaService.RequestBodySchemas.cs

@@ -235,11 +235,13 @@ await VerifyOpenApiDocument(builder, document =>
             Assert.Equal("Proposal", ((OpenApiSchemaReference)schema).Reference.Id);
             var effectiveSchema = schema;
             Assert.Collection(effectiveSchema.Properties,
-                property => {
+                property =>
+                {
                     Assert.Equal("proposalElement", property.Key);
                     Assert.Equal("Proposal", ((OpenApiSchemaReference)property.Value).Reference.Id);
                 },
-                property => {
+                property =>
+                {
                     Assert.Equal("stream", property.Key);
                     var targetSchema = property.Value;
                     Assert.Equal(JsonSchemaType.String | JsonSchemaType.Null, targetSchema.Type);
@@ -395,7 +397,15 @@ await VerifyOpenApiDocument(builder, document =>
                     Assert.Equal(JsonSchemaType.String, property.Value.Type);
                     Assert.Equal("date-time", property.Value.Format);
                     Assert.Equal("The date and time the todo item was created.", property.Value.Description);
+                },
+                property =>
+                {
+                    var reference = Assert.IsType<OpenApiSchemaReference>(property.Value);
+                    Assert.Equal("sampleEnum", property.Key);
+                    Assert.Equal("The sample enum property.", reference.Description);
                 });
+            var sampleEnumSchema = document.Components.Schemas["SampleEnum"];
+            Assert.Equal("Enum: SampleEnum", sampleEnumSchema.Description);
         });
     }
 
@@ -735,6 +745,9 @@ private class DescriptionTodo
 
         [Description("The date and time the todo item was created.")]
         public DateTime CreatedAt { get; set; }
+
+        [Description("The sample enum property.")]
+        public SampleEnum SampleEnum { get; set; }
     }
 
 #nullable enable
@@ -999,4 +1012,36 @@ internal Status FormPostWithOptionalEnumParam(
             [FromForm(Name = "status")] Status status = Status.Approved
         ) => status;
     }
+
+    [Fact]
+    public async Task GetRequestBody_HandleNullableEnumDescription()
+    {
+        // Arrange
+        var builder = CreateBuilder();
+
+        // Act
+        builder.MapPost("/", (NullableEnumModel model) => { });
+
+        // Assert
+        await VerifyOpenApiDocument(builder, document =>
+        {
+            var paths = Assert.Single(document.Paths.Values);
+            var operation = paths.Operations[HttpMethod.Post];
+
+            var modelSchema = document.Components.Schemas["SampleEnum"];
+            Assert.Equal("Enum: SampleEnum", modelSchema.Description);
+        });
+    }
+
+    private class NullableEnumModel
+    {
+        public SampleEnum? EnumProperty { get; set; }
+    }
+
+    [Description("Enum: SampleEnum")]
+    public enum SampleEnum
+    {
+        FirstValue,
+        SecondValue
+    }
 }