fix(generator): wrap enum operation responses in value property

src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiResponseGenerator.cs

@@ -208,10 +208,10 @@ public static OpenApiResponses CreateResponses(this ODataContext context, IEdmOp
                     openApiSchema.Type = JsonSchemaType.Object;
                 }
             }
-            else if (returnType.IsPrimitive())
+            else if (returnType.IsPrimitive() || returnType.IsEnum())
             {
-                // A property or operation response that is of a primitive type is represented as an object with a single name/value pair,
-                // whose name is value and whose value is a primitive value.
+                // A property or operation response that is of a primitive or enum type is represented as an object with a single name/value pair,
+                // whose name is value and whose value is a primitive or enum value.
                 schema = new OpenApiSchema
                 {
                     Type = JsonSchemaType.Object,

test/Microsoft.OpenAPI.OData.Reader.Tests/Generator/OpenApiResponseGeneratorTests.cs

@@ -448,5 +448,40 @@ public async Task CreateResponseForDeltaEdmFunctionReturnCorrectResponses(bool e
                 Assert.True(JsonNode.DeepEquals(expectedJsonNode, actualJsonNode));
             }
         }
+
+        [Fact]
+        public void CreateResponseForEdmFunctionReturningEnumWrapsInValueProperty()
+        {
+            // Arrange
+            var model = new EdmModel();
+            var enumType = new EdmEnumType("NS", "Color");
+            enumType.AddMember("Red", new EdmEnumMemberValue(0));
+            enumType.AddMember("Blue", new EdmEnumMemberValue(1));
+            model.AddElement(enumType);
+
+            var function = new EdmFunction("NS", "GetFavoriteColor", new EdmEnumTypeReference(enumType, isNullable: false), isBound: false, entitySetPathExpression: null, isComposable: true);
+            model.AddElement(function);
+
+            var context = new ODataContext(model);
+            var document = new OpenApiDocument();
+
+            // Act
+            var responses = context.CreateResponses(function, document);
+
+            // Assert
+            Assert.NotNull(responses);
+            Assert.True(responses.ContainsKey("200"));
+            var response = responses["200"];
+            Assert.NotNull(response.Content);
+            Assert.True(response.Content.ContainsKey("application/json"));
+            var mediaType = response.Content["application/json"];
+            Assert.NotNull(mediaType.Schema);
+            Assert.Equal(JsonSchemaType.Object, mediaType.Schema.Type);
+            Assert.NotNull(mediaType.Schema.Properties);
+            Assert.True(mediaType.Schema.Properties.ContainsKey("value"));
+
+            var valueSchema = mediaType.Schema.Properties["value"];
+            Assert.NotNull(valueSchema);
+        }
     }
 }