ExceptionHandler is rethrowing exceptions when mapping an exception to status code 404

[danikun]

Describe the bug

I had a lambda exception handler in my middleware pipeline to handle some custom exceptions and map them to particular status codes in the response. Since I updated from 3.1 to 5.0rc1 when I map the exception to 404, the exception is rethrown after being handled.

I have mitigated the issue with Response.CompleteAsync(), and it works when the app is running normally, but the exception is still thrown and this breaks my integration tests.

To Reproduce

The easiest way to reproduce is adding a lambda exception handler in this form:

            app.UseExceptionHandler(errorApp =>
            {
                errorApp.Run(async context =>
                {
                    var contextFeature = context.Features.Get<IExceptionHandlerFeature>();
                    context.Response.StatusCode = (int)HttpStatusCode.NotFound;
                    
                    await context.Response.WriteAsJsonAsync(new { Message = "Not found" });
                    await context.Response.CompleteAsync();
                });
            });

And create a controller throwing an exception, call this controller and see that the exception is rethrown after being handled.

Further technical details

• ASP.NET Core version: 5.0rc1
• Using VS 16.8.0 Preview 3.2

[JunTaoLuo]

I'll update the announcement when I'm back in the office and I'll close the issue once it's updated.

[jkotalik]

@Tratcher did you mean to reopen this? oops, now see you want this for announcement.

[JunTaoLuo]

Announcement aspnet/Announcements#434 has been updated.