asp .net 5 can't return json with 404 status code

[VladislavMorozov]

I use .net 5.0.202 with system.text,json.
I have exception handler

With processing errors.

(failed)net::ERR_INCOMPLETE_CHUNKED_ENCODING

[VladislavMorozov]

Other http codes (4xx) return a valid json

[VladislavMorozov]

test project
WebApplication1.zip

[fvoronin]

I did a little investigation and found that the problem occurs when we set the StatusCode = 404 in the response. In this case, the web server transmitting the response in "Transfer-Encoding: chunked" mode does not transmit a zero-length chunk at the end of the response body.

Compare. As now:

HTTP/1.1 404 Not Found
Date: Thu, 22 Apr 2021 06:40:36 GMT
Content-Type: application/problem+json
Server: Kestrel
Cache-Control: no-cache,no-store
Pragma: no-cache
Transfer-Encoding: chunked
Expires: -1

75
{"title":"title","status":404,"detail":"details","traceId":"00-93249638518c924dafd48997d28c8303-ccd2508c5de5a34d-00"}

As it should be:

HTTP/1.1 500 Internal Server Error
Date: Thu, 22 Apr 2021 06:40:03 GMT
Content-Type: application/problem+json
Server: Kestrel
Cache-Control: no-cache,no-store
Pragma: no-cache
Transfer-Encoding: chunked
Expires: -1

75
{"title":"title","status":404,"detail":"details","traceId":"00-0bad9468621ebd4981854389e389ba9d-29a0cf6cc2c0e44d-00"}
0

@Tratcher, I'd like to take a deeper look at it.

[davidfowl]

It's by design, you can disable this behavior with https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.builder.exceptionhandleroptions.allowstatuscode404response?view=aspnetcore-5.0.

[davidfowl]

@VladislavMorozov there are also built in helpers for writing JSON responses as well:

• https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.httpresponsejsonextensions.writeasjsonasync?view=aspnetcore-5.0#Microsoft_AspNetCore_Http_HttpResponseJsonExtensions_WriteAsJsonAsync_Microsoft_AspNetCore_Http_HttpResponse_System_Object_System_Type_System_Text_Json_JsonSerializerOptions_System_Threading_CancellationToken_
• https://docs.microsoft.com/en-us/aspnet/core/web-api/route-to-code?view=aspnetcore-5.0#create-json-web-apis

[VladislavMorozov]

But before it works on .net 5 :) Thanks for help

[VladislavMorozov]

@davidfowl It works with https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.builder.exceptionhandleroptions.allowstatuscode404response?view=aspnetcore-5.0
Thanks. But I don't understand how this works on previous versions of .net 5 :)

[davidfowl]

But I don't understand how this works on previous versions of .net 5 :)

Because we changed the behavior. https://docs.microsoft.com/en-us/dotnet/core/compatibility/aspnet-core/5.0/middleware-exception-handler-throws-original-exception

We added this API later but never updated the original change it seems:

#26567

cc @JunTaoLuo @Tratcher

[VladislavMorozov]

@davidfowl It's okay that server return (failed)net::ERR_INCOMPLETE_CHUNKED_ENCODING ?

[Tratcher]

@davidfowl It's okay that server return (failed)net::ERR_INCOMPLETE_CHUNKED_ENCODING ?

That means the rethrown exception caused the connection to be closed and the response aborted. There's another issue where we disabled the 404 rethrow if there was a body to prevent this kind of abort.

[Tratcher]

Correction, @JunTaoLuo and I talked about adding a HasStarted check here, but it doesn't look like it's happened yet.

aspnetcore/src/Middleware/Diagnostics/src/ExceptionHandler/ExceptionHandlerMiddleware.cs

Line 135 in 9817a81

if (context.Response.StatusCode != StatusCodes.Status404NotFound || _options.AllowStatusCode404Response)

@JunTaoLuo do you remember if there's another issue for that, or did we change our minds?