chore: switch XRefMap serialization logics to use System.Text.Json

src/Docfx.Build/XRefMaps/XRefMapDownloader.cs

@@ -128,7 +128,7 @@ private static async ValueTask<IXRefContainer> ReadLocalFileAsync(string filePat
                     switch (Path.GetExtension(Path.GetFileNameWithoutExtension(filePath)).ToLowerInvariant())
                     {
                         case ".json":
-                            return await SystemTextJsonUtility.DeserializeAsync<XRefMap>(stream, token);
+                            return await JsonUtility.DeserializeAsync<XRefMap>(stream, token);
                         case ".yml":
                         default:
                             {
@@ -141,7 +141,7 @@ private static async ValueTask<IXRefContainer> ReadLocalFileAsync(string filePat
             case ".json":
                 {
                     using var stream = File.OpenRead(filePath);
-                    return await SystemTextJsonUtility.DeserializeAsync<XRefMap>(stream, token);
+                    return await JsonUtility.DeserializeAsync<XRefMap>(stream, token);
                 }
 
             case ".yml":
@@ -172,7 +172,7 @@ private static async Task<XRefMap> DownloadFromWebAsync(Uri uri, CancellationTok
         {
             case ".json":
                 {
-                    var xrefMap = await SystemTextJsonUtility.DeserializeAsync<XRefMap>(stream, token);
+                    var xrefMap = await JsonUtility.DeserializeAsync<XRefMap>(stream, token);
                     xrefMap.BaseUrl = ResolveBaseUrl(xrefMap, uri);
                     return xrefMap;
                 }

src/Docfx.Common/Json/JsonUtility.cs

@@ -44,6 +44,14 @@ public static T Deserialize<T>(TextReader reader)
             return NewtonsoftJsonUtility.Deserialize<T>(reader);
     }
 
+    internal static ValueTask<T> DeserializeAsync<T>(Stream stream, CancellationToken cancellationToken)
+    {
+        if (IsSystemTextJsonSupported<T>())
+            return SystemTextJsonUtility.DeserializeAsync<T>(stream, cancellationToken);
+        else
+            throw new NotSupportedException();
+    }
+
     public static string ToJsonString<T>(this T graph)
     {
         if (IsSystemTextJsonSupported<T>())
@@ -79,9 +87,12 @@ private static bool IsSupported()
             var type = typeof(T);
             var fullName = type.FullName;
 
+            // TODO: Return `true` for types that support serialize/deserializenon with System.Text.Json.
             switch (fullName)
             {
-                // TODO: Return `true` for types that support serialize/deserializenon with System.Text.Json.
+                case "Docfx.Build.Engine.XRefMap":
+                    return true;
+
                 default:
                     return false;
             }

test/docfx.Tests/SerializationTests/JsonSerializationTest.XRefMap.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Docfx;
+using Docfx.Build.Engine;
+using Docfx.Common;
+using Docfx.Plugins;
+using FluentAssertions;
+
+namespace docfx.Tests;
+
+public partial class JsonSerializationTest
+{
+    [Theory]
+    [TestData<XRefMap>]
+    public void JsonSerializationTest_XRefMap(string path)
+    {
+        // Arrange
+        var model = TestData.Load<XRefMap>(path);
+
+        // Act/Assert
+        ValidateJsonRoundTrip(model);
+    }
+}