graphql/src/Language/GraphQL/Error.hs

86 lines
3.0 KiB
Haskell
Raw Normal View History

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
2019-09-20 08:47:14 +02:00
-- | Error handling.
module Language.GraphQL.Error
2019-07-14 05:58:05 +02:00
( parseError
, CollectErrsT
, addErr
, addErrMsg
, runCollectErrs
, runAppendErrs
2019-07-23 06:04:33 +02:00
, singleError
2019-07-14 05:58:05 +02:00
) where
import qualified Data.Aeson as Aeson
import Data.Text (Text)
import Data.Void (Void)
2019-06-28 11:12:28 +02:00
import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.State ( StateT
, modify
, runStateT
)
import Text.Megaparsec ( ParseErrorBundle(..)
, SourcePos(..)
, errorOffset
, parseErrorTextPretty
, reachOffset
, unPos
)
-- | Wraps a parse error into a list of errors.
parseError :: Applicative f => ParseErrorBundle Text Void -> f Aeson.Value
parseError ParseErrorBundle{..} =
pure $ Aeson.object [("errors", Aeson.toJSON $ fst $ foldl go ([], bundlePosState) bundleErrors)]
where
errorObject s SourcePos{..} = Aeson.object
[ ("message", Aeson.toJSON $ init $ parseErrorTextPretty s)
, ("line", Aeson.toJSON $ unPos sourceLine)
, ("column", Aeson.toJSON $ unPos sourceColumn)
]
go (result, state) x =
let (sourcePosition, _, newState) = reachOffset (errorOffset x) state
in (errorObject x sourcePosition : result, newState)
2019-06-28 11:12:28 +02:00
-- | A wrapper to pass error messages around.
type CollectErrsT m = StateT [Aeson.Value] m
-- | Adds an error to the list of errors.
2019-06-28 11:12:28 +02:00
addErr :: Monad m => Aeson.Value -> CollectErrsT m ()
addErr v = modify (v :)
2019-07-23 06:04:33 +02:00
makeErrorMessage :: Text -> Aeson.Value
makeErrorMessage s = Aeson.object [("message", Aeson.toJSON s)]
-- | Constructs a response object containing only the error with the given
-- message.
singleError :: Text -> Aeson.Value
singleError message = Aeson.object
[ ("errors", Aeson.toJSON [makeErrorMessage message])
]
-- | Convenience function for just wrapping an error message.
2019-06-28 11:12:28 +02:00
addErrMsg :: Monad m => Text -> CollectErrsT m ()
2019-07-23 06:04:33 +02:00
addErrMsg = addErr . makeErrorMessage
2019-06-28 11:12:28 +02:00
-- | Appends the given list of errors to the current list of errors.
appendErrs :: Monad m => [Aeson.Value] -> CollectErrsT m ()
appendErrs errs = modify (errs ++)
-- | Runs the given query computation, but collects the errors into an error
-- list, which is then sent back with the data.
runCollectErrs :: Monad m => CollectErrsT m Aeson.Value -> m Aeson.Value
runCollectErrs res = do
(dat, errs) <- runStateT res []
if null errs
then return $ Aeson.object [("data", dat)]
else return $ Aeson.object [("data", dat), ("errors", Aeson.toJSON $ reverse errs)]
-- | Runs the given computation, collecting the errors and appending them
-- to the previous list of errors.
runAppendErrs :: Monad m => CollectErrsT m a -> CollectErrsT m a
runAppendErrs f = do
(v, errs) <- lift $ runStateT f []
appendErrs errs
return v