Wreq: Stop 404s throwing exceptions - haskell

Question

I am trying to test broken links but, when I use Wreq's get method and run into a 404, I get an exception (see bottom) rather than a statusCode to handle. Only 200s seem to be returned.
I tried to follow the error-handling code in the tutorial but I can't find a way to return the same type as get u. Moreover, this seems to be more complexity than I need in this instance.
How can I simply prevent the exception and just return the responseStatus as is
verifySeatme :: Maybe URL -> IO UrlStatus
verifySeatme url = do
case url of
Nothing -> return None
Just "" -> return None
Just u -> do
seatmeResp <- get u --`E.catch` handler
-- r ^? responseBody . key "url"
-- could also check for redirect to errorPage.aspx
if seatmeResp ^. W.responseStatus . statusCode == 200
then return (Working u)
else return Broken
where
handler e#(StatusCodeException s respHeaders _) =
do
return respHeaders
Here is the exception thrown, and you can see it has the stateCode i want
*Main> re <- get "https://www.seatme.nl/restaurant/1371/Londen.htm"
*** Exception: StatusCodeException (Status {statusCode = 404, statusMessage = "Not Found"}) [("Cache-Control","private"),....
Yuras suggested using options, but I have been unable to work from the example using params to one using checkStatus :: Lens' Options (Maybe StatusChecker):
getData :: IO Restos
getData = do
let opts = defaults & customStatusHandler
jdata <- asJSON =<< getWith opts "http://localhost/restos-short.json" :: IO Resp
let
restos = jdata ^. W.responseBody
verified <- mapM processEntry restos
return verified
-- type StatusChecker = Status -> ResponseHeaders -> CookieJar -> Maybe SomeException
customStatusHandler :: W.StatusChecker
customStatusHandler st res _ =
Just res

Answer 1

NOTE: the answer is outdated, see other answers.
I never used Wreq, but it looks like you should use getWith to pass custom options and checkStatus to configure status handling.
An example:
getWith (set checkStatus (Just $ \_ _ _ -> Nothing) defaults)
"http://google.com/hello/world"
The \_ _ _ -> Nothing is a function to check status code, see StatusChecker. It returns nothing indicating that any status code is OK.

Answer 2

To expand on the answer by Evelyn Schneider, I got this to work with
r <- getWith opts url
where
opts = set Network.Wreq.checkResponse (Just $ \_ _ -> return ()) defaults

Answer 3

For posterity: newer versions of wreq (starting with 0.5) have replaced checkStatus with checkResponse, which takes different arguments. An equivalent to Yuras' answer would now be:
getWith opts url
where opts = set checkResponse (\_ _ -> return ()) defaults

Answer 4

Here's the checkStatus function I ended up with after researching a bit. I couldn't figure out how to convert a HttpException to a SomeException, but then I found Control.Monad.Catch.SomeException. This will ignore 404s and re-throw all other exceptions.
import Network.HTTP.Client.Types
import Network.HTTP.Types.Status
import Network.HTTP.Types.Header
import qualified Control.Exception as E
import Control.Monad.Catch (SomeException(..))
notFoundMeansNothing :: Status -> ResponseHeaders -> CookieJar -> Maybe E.SomeException
notFoundMeansNothing s h c
| s == status404 = Nothing
| otherwise =
if statusIsClientError s || statusIsServerError s then
Just . SomeException $ StatusCodeException s h c
else
Nothing