ConvertToJson not escaping invalid unicode control codes

[samcarton]

Bug description

ConvertToJson only seems to handle escaping \r \n \t \f \b - other unicode control codes come through unescaped.

Repro steps

• referencing System.Text.Json

public class Test
{
	public string Value { get; set; }
}


void Main()
{
	// write msgpack
	var test = new Test { Value = "\u0011" };
	var testJson = System.Text.Json.JsonSerializer.Serialize(test);
	var msgpackData = MessagePack.MessagePackSerializer.ConvertFromJson(testJson);


	// read msgpack
	var msgpackJson = MessagePack.MessagePackSerializer.ConvertToJson(msgpackData);

	// throws exception: '0x11' is invalid within a JSON string. The string should be correctly escaped. Path: $.Value | LineNumber: 0 | BytePositionInLine: 10.
	var testOut = System.Text.Json.JsonSerializer.Deserialize<Test>(msgpackJson);
}

Expected behavior

• Escape invalid unicode characters

Actual behavior

• invalid unicode characters not escaped
• Version used: 2.5.140
• Runtime: .NET 7

Additional context

• We are using json to read\write between our C# classes and messagepack because the Union attribute isn't really a good solution when there are hundreds of concrete implementations of an interface or set of interfaces.
• To get around this currently we need to strip out invalid characters with Regex. See List of controls codes.
• System.Text.Json does handle escaping unicode control characters, and is able to deserialize its own output back. It's just when the json comes through MessagePackSerializer.ConvertToJson the characters are not escaped.

[AArnott]

This isn't a JSON serialization library. The JSON support it has is merely included for debuggability so that you can see what's being serialized in what otherwise is an unreadable binary format.
So this is a low priority that we wouldn't get to. If you wanted to send a PR to address this though, we'd review it. But I can't promise we'd merge it.