HttpClientJsonExtensions.PostAsJsonAsync Throws NullReferenceException When Serializing the Property/Value Message = "Message:"

[xcjs]

We have a LogMessage record defined as:

public record LogMessage
{
       // LogLevel is an enumeration.
	public LogLevel LogLevel { get; set; }
	public Exception? Exception { get; set; }
	public string? Message { get; set; }
}

I have so far narrowed this down to using PostAsJsonAsync with the following characteristics:

A NullReferenceException is thrown from the MockHttpMessageHandler when we assign the string literal "Message:" to LogMessage.Message.

await _http.PostAsJsonAsync(
      RoutesAndFunctions.LogMessagesFunctionUrl,
      new LogMessage
      {
         LogLevel = logLevel,
          Exception = null,
          Message = "Message:"
      });

The default HttpMessageHandler in .NET Core 6 does not exhibit the same behavior.

[richardszalay]

Can you provide the stack trace of the exception and provide a self-contained minimal repro? The sample test passes.

public enum LogLevel
{
    Information = 1
}

public record LogMessage
{
    // LogLevel is an enumeration.
    public LogLevel LogLevel { get; set; }
    public Exception? Exception { get; set; }
    public string? Message { get; set; }
}

public class Issue108Tests
{
    [Fact]
    public async Task Can_post_specific_message()
    {
        var mockHttp = new MockHttpMessageHandler();

        mockHttp.When("http://localhost/test")
            .Respond(HttpStatusCode.OK);

        var client = mockHttp.ToHttpClient();

        var response = await client.PostAsJsonAsync("http://localhost/test",
            new LogMessage
            {
                LogLevel = LogLevel.Information,
                Exception = null,
                Message = "Message:"
            });

        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
    }
}

[richardszalay]

I'm going to close this issue as I haven't heard from you with a repro for the issue.