OnError endpoint and exception map

[Kromi75]

I'm using the OnError endpoint to write exceptions to serilog. Additionally I have mapped ValidationException to status code 400. In order to test my GlobalExeptionHandler configuration I have distributed some new ApplicationException("...") in my code. But these never get logged. Only the ValidationExceptions are. If I add a map for ApplicationException, these get logged, too. Is this the intended behavior?

[josephwoodward]

Yes, if I'm understanding you correctly then this is the expected behaviour. If an exception isn't mapped then the response GlobalExceptionHandler will return to callers is the default response.

Take the following example:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
app.UseGlobalExceptionHandler(x => {
    x.ContentType = "application/json";
   // This is a default error response
    x.ResponseBody(s => JsonConvert.SerializeObject(new
    {
        Message = "An error occurred whilst processing your request"
    }));

    x.Map<ValidationException>().ToStatusCode(StatusCodes.Status400BadRequest);
});

     // Returns 400 plus whatever is in default response ResponseBody (eg: "An error occurred whilst processing your request")
    app.Map("/validationerror", x => x.Run(y => throw new ValidationException()));

   // returns whatever is configured in the default response ResponseBody (eg: "An error occurred whilst processing your request")
    app.Map("/applicationerror", x => x.Run(y => throw new ApplicationException()));
}

I hope this helps, let me know if you have any further problems or questions.

[Kromi75]

I'm not sure if we talk about the same thing. Please have a look at this snippet:

      app.UseGlobalExceptionHandler(
        x =>
        {
          x.ContentType = "application/json";
          x.ResponseBody(s => JsonConvert.SerializeObject(new { Message = "An error occurred whilst processing your request" }));

          x.OnError((exception, httpContext) =>
          {
            // This is not executed for exceptions of type ApplicationException.
            Log.Error("An error occurred. {Exception}", exception);
            return Task.CompletedTask;
          });

          // Validation-Exceptions are to be returned as Bad Request.
          x.Map<ValidationException>().ToStatusCode(StatusCodes.Status400BadRequest);
        },
        NullLoggerFactory.Instance);

With this configuration, the OnError func is called for exceptions of type ValidationException, but not for ApplicationException. So I assume that the OnError func is only called for exception types a mapping is defined for. Am I right? Or am I doing it completely wrong? BTW, what I'm trying to achieve is that all exceptions are logged exactly once. That's why I passed a NullLoggerFactory to avoid having all exceptions logged as unhandled exceptions.

[josephwoodward]

This should be fixed in the v5 release which will be going out in the next day or so.

[Kromi75]

Great, thank you.