Merge pull request #1439 from microsoft/mk/fix-link-extension-serialization

Fix link extensions serialization

Author: MaggieKimani1

src/Microsoft.OpenApi/Models/OpenApiLink.cs

@@ -147,6 +147,9 @@ public void SerializeAsV3WithoutReference(IOpenApiWriter writer)
             // server
             writer.WriteOptionalObject(OpenApiConstants.Server, Server, (w, s) => s.SerializeAsV3(w));
 
+            // specification extensions
+            writer.WriteExtensions(Extensions, OpenApiSpecVersion.OpenApi3_0);
+
             writer.WriteEndObject();
         }
 

test/Microsoft.OpenApi.Tests/Models/OpenApiLinkTests.cs

@@ -17,7 +17,7 @@ namespace Microsoft.OpenApi.Tests.Models
     [UsesVerify]
     public class OpenApiLinkTests
     {
-        public static OpenApiLink AdvancedLink = new()
+        public static readonly OpenApiLink AdvancedLink = new()
         {
             OperationId = "operationId1",
             Parameters =
@@ -41,7 +41,7 @@ public class OpenApiLinkTests
             }
         };
 
-        public static OpenApiLink ReferencedLink = new()
+        public static readonly OpenApiLink ReferencedLink = new()
         {
             Reference = new()
             {
@@ -120,5 +120,35 @@ public async Task SerializeReferencedLinkAsV3JsonWithoutReferenceWorksAsync(bool
             // Assert
             await Verifier.Verify(outputStringWriter).UseParameters(produceTerseOutput);
         }
+
+        [Fact]
+        public void LinkExtensionsSerializationWorks()
+        {
+            // Arrange
+            var link = new OpenApiLink()
+            {
+                Extensions = {
+                { "x-display", new OpenApiString("Abc") }
+}
+            };
+
+            var expected =
+                """
+                {
+                  "x-display": "Abc"
+                }
+                """;
+
+            var outputStringWriter = new StringWriter(CultureInfo.InvariantCulture);
+            var writer = new OpenApiJsonWriter(outputStringWriter, new() { Terse = false });
+
+
+            // Act
+            link.SerializeAsV3(writer);
+
+            // Assert
+            var actual = outputStringWriter.ToString();
+            Assert.Equal(expected.MakeLineBreaksEnvironmentNeutral(), actual.MakeLineBreaksEnvironmentNeutral());
+        }
     }
 }