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{- This Source Code Form is subject to the terms of the Mozilla Public License,
v. 2.0. If a copy of the MPL was not distributed with this file, You can
obtain one at https://mozilla.org/MPL/2.0/. -}
{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE RecordWildCards #-}
-- | Error handling.
module Language.GraphQL.Error
( Error(..)
, Path(..)
, ResolverException(..)
, Response(..)
, ResponseEventStream
, parseError
) where
import Conduit
import Control.Exception (Exception(..))
import Data.Sequence (Seq(..), (|>))
import qualified Data.Sequence as Seq
import Data.Text (Text)
import qualified Data.Text as Text
import Language.GraphQL.AST (Location(..))
import Language.GraphQL.Execute.Coerce
import Prelude hiding (null)
import Text.Megaparsec
( ParseErrorBundle(..)
, PosState(..)
, SourcePos(..)
, errorOffset
, parseErrorTextPretty
, reachOffset
, unPos
)
-- | Wraps a parse error into a list of errors.
parseError :: (Applicative f, Serialize a)
=> ParseErrorBundle Text Void
-> f (Response a)
parseError ParseErrorBundle{..} =
pure $ Response null $ fst
$ foldl go (Seq.empty, bundlePosState) bundleErrors
where
errorObject s SourcePos{..} = Error
{ message = Text.pack $ init $ parseErrorTextPretty s
, locations = [Location (unPos' sourceLine) (unPos' sourceColumn)]
, path = []
}
unPos' = fromIntegral . unPos
go (result, state) x =
let (_, newState) = reachOffset (errorOffset x) state
sourcePosition = pstateSourcePos newState
in (result |> errorObject x sourcePosition, newState)
-- | If an error can be associated to a particular field in the GraphQL result,
-- it must contain an entry with the key path that details the path of the
-- response field which experienced the error. This allows clients to identify
-- whether a null result is intentional or caused by a runtime error.
data Path
= Segment Text -- ^ Field name.
| Index Int -- ^ List index if a field returned a list.
deriving (Eq, Show)
-- | @GraphQL@ error.
data Error = Error
{ message :: Text
, locations :: [Location]
, path :: [Path]
} deriving (Eq, Show)
-- | The server\'s response describes the result of executing the requested
-- operation if successful, and describes any errors encountered during the
-- request.
data Response a = Response
{ data' :: a
, errors :: Seq Error
} deriving (Eq, Show)
-- | Each event in the underlying Source Stream triggers execution of the
-- subscription selection set. The results of the execution generate a Response
-- Stream.
type ResponseEventStream m a = ConduitT () (Response a) m ()
-- | Only exceptions that inherit from 'ResolverException' a cought by the
-- executor.
data ResolverException = forall e. Exception e => ResolverException e
instance Show ResolverException where
show (ResolverException e) = show e
instance Exception ResolverException
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