Resolve references to child properties of Response fragments

Author: simon-pearson-lmk

src/Microsoft.OpenApi/Extensions/OpenApiReferencableExtensions.cs

@@ -38,6 +38,10 @@ public static IOpenApiReferenceable ResolveReference(this IOpenApiReferenceable
                 {
                     return ResolveReferenceOnParameterElement((OpenApiParameter)element, jsonPointer);
                 }
+                if (element.GetType() == typeof(OpenApiResponse))
+                {
+                    return ResolveReferenceOnResponseElement((OpenApiResponse)element, jsonPointer);
+                }
             }
             catch (KeyNotFoundException)
             {
@@ -93,5 +97,34 @@ private static IOpenApiReferenceable ResolveReferenceOnParameterElement(OpenApiP
                     throw new OpenApiException(string.Format(SRResource.InvalidReferenceId, jsonPointer));
             }
         }
+
+        private static IOpenApiReferenceable ResolveReferenceOnResponseElement(OpenApiResponse responseElement, string jsonPointer)
+        {
+            if (string.IsNullOrEmpty(jsonPointer))
+            {
+                throw new OpenApiException(string.Format(SRResource.InvalidReferenceId, jsonPointer));
+            }
+            var jsonPointerTokens = jsonPointer.Split('/');
+            var propertyName = jsonPointerTokens.ElementAtOrDefault(1);
+            switch (propertyName)
+            {
+                case OpenApiConstants.Headers:
+                    {
+                        if (jsonPointerTokens.Length < 3)
+                            throw new OpenApiException(string.Format(SRResource.InvalidReferenceId, jsonPointer));
+                        var mapKey = jsonPointerTokens.ElementAtOrDefault(2);
+                        return responseElement.Headers[mapKey];
+                    }
+                case OpenApiConstants.Links:
+                    {
+                        if (jsonPointerTokens.Length < 3)
+                            throw new OpenApiException(string.Format(SRResource.InvalidReferenceId, jsonPointer));
+                        var mapKey = jsonPointerTokens.ElementAtOrDefault(2);
+                        return responseElement.Links[mapKey];
+                    }
+                default:
+                    throw new OpenApiException(string.Format(SRResource.InvalidReferenceId, jsonPointer));
+            }
+        }
     }
 }

test/Microsoft.OpenApi.Tests/Workspaces/OpenApiReferencableTests.cs

@@ -35,7 +35,17 @@ public class OpenApiReferencableTests
             }
         };
         private static readonly OpenApiRequestBody _requestBodyFragment = new OpenApiRequestBody();
-        private static readonly OpenApiResponse _responseFragment = new OpenApiResponse();
+        private static readonly OpenApiResponse _responseFragment = new OpenApiResponse()
+        {
+            Headers = new Dictionary<string, OpenApiHeader>
+            {
+                { "header1", new OpenApiHeader() }
+            },
+            Links = new Dictionary<string, OpenApiLink>
+            {
+                { "link1", new OpenApiLink() }
+            }
+        };
         private static readonly OpenApiSchema _schemaFragment = new OpenApiSchema();
         private static readonly OpenApiSecurityScheme _securitySchemeFragment = new OpenApiSecurityScheme();
         private static readonly OpenApiTag _tagFragment = new OpenApiTag();
@@ -54,6 +64,8 @@ public class OpenApiReferencableTests
             new object[] { _parameterFragment, "/examples/example1", _parameterFragment.Examples["example1"] },
             new object[] { _requestBodyFragment, "/", _requestBodyFragment },
             new object[] { _responseFragment, "/", _responseFragment },
+            new object[] { _responseFragment, "/headers/header1", _responseFragment.Headers["header1"] },
+            new object[] { _responseFragment, "/links/link1", _responseFragment.Links["link1"] },
             new object[] { _schemaFragment, "/", _schemaFragment},
             new object[] { _securitySchemeFragment, "/", _securitySchemeFragment},
             new object[] { _tagFragment, "/", _tagFragment},
@@ -90,7 +102,16 @@ public void ResolveReferenceCanResolveValidJsonPointers(
             new object[] { _parameterFragment, "/a" },
             new object[] { _parameterFragment, "/examples" },
             new object[] { _parameterFragment, "/examples/" },
-            new object[] { _parameterFragment, "/examples/a" }
+            new object[] { _parameterFragment, "/examples/a" },
+            new object[] { _responseFragment, null },
+            new object[] { _responseFragment, "" },
+            new object[] { _responseFragment, "/a" },
+            new object[] { _responseFragment, "/headers" },
+            new object[] { _responseFragment, "/headers/" },
+            new object[] { _responseFragment, "/headers/a" },
+            new object[] { _responseFragment, "/content" },
+            new object[] { _responseFragment, "/content/" },
+            new object[] { _responseFragment, "/content/a" },
 
         };