Leave the writer empty when Newtonsoft TrySerialize fails [patch]

Essentials.SerializationProviders.NewtonsoftJson/NewtonsoftJsonSerializationProvider.cs

@@ -4,6 +4,7 @@ namespace ktsu.Essentials.SerializationProviders.NewtonsoftJson;
 
 using ktsu.Essentials;
 using System;
+using System.Globalization;
 using System.IO;
 using System.Text;
 using Newtonsoft.Json;
@@ -39,11 +40,17 @@ public bool TrySerialize(object obj, TextWriter writer)
 
 		try
 		{
-			// The caller owns the writer, so disposing the JSON writer must not close it.
-			using DepthLimitedJsonTextWriter jsonWriter = new(writer, MaxDepth) { CloseOutput = false };
-			JsonSerializer serializer = JsonSerializer.Create(settings);
-			serializer.Serialize(jsonWriter, obj);
-			jsonWriter.Flush();
+			// Serialize into a local buffer and copy it to the caller's writer only on success.
+			// Disposing a JsonTextWriter closes any object or array a failure left open, so
+			// streaming straight into the caller's writer would leave truncated JSON that parses.
+			using StringWriter buffer = new(CultureInfo.InvariantCulture);
+			using (DepthLimitedJsonTextWriter jsonWriter = new(buffer, MaxDepth))
+			{
+				JsonSerializer serializer = JsonSerializer.Create(settings);
+				serializer.Serialize(jsonWriter, obj);
+			}
+
+			writer.Write(buffer.ToString());
 			return true;
 		}
 		catch (JsonSerializationException)

Essentials.Tests/NewtonsoftJsonSerializationProviderTests.cs

@@ -30,6 +30,18 @@ public void TrySerialize_WriterThrowingIOException_ReturnsFalse()
 		Assert.IsFalse(provider.TrySerialize(new { A = 1 }, writer));
 	}
 
+	[TestMethod]
+	public void TrySerialize_CyclicObject_ReturnsFalseAndWritesNothing()
+	{
+		NewtonsoftJsonSerializationProvider provider = new();
+		Node node = new() { Name = "a" };
+		node.Next = node;
+		using StringWriter writer = new();
+
+		Assert.IsFalse(provider.TrySerialize(node, writer));
+		Assert.AreEqual(string.Empty, writer.ToString());
+	}
+
 	[TestMethod]
 	[DataRow(64)]
 	[DataRow(65)]