chore: cleanup

Author: MaggieKimani1

src/Microsoft.OpenApi.Hidi/OpenApiService.cs

@@ -210,7 +210,10 @@ private static async Task WriteOpenApiAsync(HidiOptions options, OpenApiFormat o
 
                 var stopwatch = new Stopwatch();
                 stopwatch.Start();
-                await document.SerializeAsync(writer, openApiVersion, cancellationToken).ConfigureAwait(false);
+                if (document is not null)
+                {
+                    await document.SerializeAsync(writer, openApiVersion, cancellationToken).ConfigureAwait(false);
+                }
                 stopwatch.Stop();
 
                 logger.LogTrace("Finished serializing in {ElapsedMilliseconds}ms", stopwatch.ElapsedMilliseconds);

src/Microsoft.OpenApi/Extensions/StringExtensions.cs

@@ -19,7 +19,7 @@ internal static class StringExtensions
     {
         private static readonly ConcurrentDictionary<Type, ReadOnlyDictionary<string, object>> EnumDisplayCache = new();
 
-        internal static bool TryGetEnumFromDisplayName<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicFields)] T>(this string? displayName, ParsingContext parsingContext, out T result) where T : Enum
+        internal static bool TryGetEnumFromDisplayName<[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicFields)] T>(this string? displayName, ParsingContext parsingContext, out T? result) where T : Enum
         {
             if (TryGetEnumFromDisplayName(displayName, out result))
             {

test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt

@@ -174,11 +174,11 @@ namespace Microsoft.OpenApi.Extensions
             where T : Microsoft.OpenApi.Interfaces.IOpenApiSerializable { }
         public static System.Threading.Tasks.Task<string> SerializeAsync<T>(this T element, Microsoft.OpenApi.OpenApiSpecVersion specVersion, Microsoft.OpenApi.OpenApiFormat format, System.Threading.CancellationToken cancellationToken = default)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiSerializable { }
-        public static System.Threading.Tasks.Task SerializeAsync<T>(this T? element, Microsoft.OpenApi.Writers.IOpenApiWriter writer, Microsoft.OpenApi.OpenApiSpecVersion specVersion, System.Threading.CancellationToken cancellationToken = default)
+        public static System.Threading.Tasks.Task SerializeAsync<T>(this T element, Microsoft.OpenApi.Writers.IOpenApiWriter writer, Microsoft.OpenApi.OpenApiSpecVersion specVersion, System.Threading.CancellationToken cancellationToken = default)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiSerializable { }
         public static System.Threading.Tasks.Task SerializeAsync<T>(this T element, System.IO.Stream stream, Microsoft.OpenApi.OpenApiSpecVersion specVersion, Microsoft.OpenApi.OpenApiFormat format, System.Threading.CancellationToken cancellationToken = default)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiSerializable { }
-        public static System.Threading.Tasks.Task SerializeAsync<T>(this T element, System.IO.Stream stream, Microsoft.OpenApi.OpenApiSpecVersion specVersion, Microsoft.OpenApi.OpenApiFormat format, Microsoft.OpenApi.Writers.OpenApiWriterSettings? settings, System.Threading.CancellationToken cancellationToken = default)
+        public static System.Threading.Tasks.Task SerializeAsync<T>(this T element, System.IO.Stream stream, Microsoft.OpenApi.OpenApiSpecVersion specVersion, Microsoft.OpenApi.OpenApiFormat format, Microsoft.OpenApi.Writers.OpenApiWriterSettings? settings = null, System.Threading.CancellationToken cancellationToken = default)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiSerializable { }
     }
     public static class OpenApiServerExtensions