servant-client doesn't return envelopes for non-2xx status codes

[bergmark]

Full reproduction: https://github.com/bergmark/sce

Using servant-0.13.1 and servant-checked-exceptions-2.0.0.0

data BadReq = BadReq deriving Show

deriveJSON defaultOptions ''BadReq

instance ErrStatus BadReq where toErrStatus BadReq = badRequest400

type API = Throws BadReq :> Get '[JSON] Value

api :: Proxy API
api = Proxy

server :: Server API
server = pureErrEnvelope BadReq

main :: IO ()
main = do
  tid <- forkIO (run 8080 $ serve api server)
  manager' <- newManager defaultManagerSettings
  print =<< runClientM (client api) (mkClientEnv manager' (BaseUrl Http "localhost" 8080 ""))
  killThread tid

I expected this to print the Error envelope but instead I get

Left (FailureResponse (Response {responseStatusCode = Status {statusCode = 400, statusMessage = "Bad Request"}, responseHeaders = fromList [("Transfer-Encoding","chunked"),("Date","Sun, 15 Jul 2018 17:53:24 GMT"),("Server","Warp/3.2.22"),("Content-Type","application/json;charset=utf-8")], responseHttpVersion = HTTP/1.1, responseBody = "{\"err\":[]}"}))

If i change the ErrStatus instance to return ok200 I get the envelope as expected:

Right (ErrEnvelope (Identity BadReq))

Is there something I'm missing?

[cdepillabout]

I have responded to this here: bergmark/sce#1.

[cdepillabout]

This also causes the example to fail:

$ stack exec -- servant-checked-exceptions-example-client foobar
Got a ServantErr: FailureResponse (Response {responseStatusCode = Status {statusCode = 404, statusMessage = "Not Found"}, responseHeaders = fromList [("Transfer-Encoding","chunked"),("Date","Mon, 16 Jul 2018 02:26:30 GMT"),("Server","Warp/3.2.22"),("Content-Type","application/json;charset=utf-8")], responseHttpVersion = HTTP/1.1, responseBody = "{\"err\":\"BadSearchTermErr\"}"})

I think for now, if you want to set exception statuses to something other than http 200, servant-client is not going to work correctly.

I said this on bergmark/sce#1 as well, but if someone wants to create an issue on the servant repo about this, I am willing to do the work to get servant-checked-exceptions fixed.

[bergmark]

Thanks a lot for digging into this!

I'll file an issue upstream.

[cdepillabout]

This was also reported by @jonathanknowles in #28.