142 lines
4.5 KiB
Haskell
142 lines
4.5 KiB
Haskell
{-# LANGUAGE DuplicateRecordFields #-}
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{-# LANGUAGE ExistentialQuantification #-}
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{-# LANGUAGE RecordWildCards #-}
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-- | Error handling.
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module Language.GraphQL.Error
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( CollectErrsT
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, Error(..)
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, Path(..)
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, Resolution(..)
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, ResolverException(..)
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, Response(..)
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, ResponseEventStream
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, addErr
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, addErrMsg
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, parseError
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, runCollectErrs
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, singleError
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) where
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import Conduit
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import Control.Exception (Exception(..))
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import Control.Monad.Trans.State (StateT, modify, runStateT)
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import Data.HashMap.Strict (HashMap)
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import Data.Sequence (Seq(..), (|>))
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import qualified Data.Sequence as Seq
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import Data.Text (Text)
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import qualified Data.Text as Text
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import Language.GraphQL.AST (Location(..), Name)
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import Language.GraphQL.Execute.Coerce
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import qualified Language.GraphQL.Type.Schema as Schema
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import Prelude hiding (null)
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import Text.Megaparsec
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( ParseErrorBundle(..)
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, PosState(..)
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, SourcePos(..)
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, errorOffset
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, parseErrorTextPretty
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, reachOffset
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, unPos
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)
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-- | Executor context.
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data Resolution m = Resolution
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{ errors :: Seq Error
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, types :: HashMap Name (Schema.Type m)
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}
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-- | Wraps a parse error into a list of errors.
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parseError :: (Applicative f, Serialize a)
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=> ParseErrorBundle Text Void
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-> f (Response a)
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parseError ParseErrorBundle{..} =
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pure $ Response null $ fst
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$ foldl go (Seq.empty, bundlePosState) bundleErrors
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where
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errorObject s SourcePos{..} = Error
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{ message = Text.pack $ init $ parseErrorTextPretty s
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, locations = [Location (unPos' sourceLine) (unPos' sourceColumn)]
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, path = []
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}
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unPos' = fromIntegral . unPos
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go (result, state) x =
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let (_, newState) = reachOffset (errorOffset x) state
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sourcePosition = pstateSourcePos newState
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in (result |> errorObject x sourcePosition, newState)
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-- | A wrapper to pass error messages around.
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type CollectErrsT m = StateT (Resolution m) m
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-- | Adds an error to the list of errors.
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{-# DEPRECATED #-}
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addErr :: Monad m => Error -> CollectErrsT m ()
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addErr v = modify appender
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where
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appender :: Monad m => Resolution m -> Resolution m
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appender resolution@Resolution{..} = resolution{ errors = errors |> v }
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{-# DEPRECATED #-}
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makeErrorMessage :: Text -> Error
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makeErrorMessage s = Error s [] []
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-- | Constructs a response object containing only the error with the given
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-- message.
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{-# DEPRECATED #-}
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singleError :: Serialize a => Text -> Response a
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singleError message = Response null $ Seq.singleton $ Error message [] []
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-- | Convenience function for just wrapping an error message.
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{-# DEPRECATED #-}
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addErrMsg :: (Monad m, Serialize a) => Text -> CollectErrsT m a
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addErrMsg errorMessage = (addErr . makeErrorMessage) errorMessage >> pure null
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-- | If an error can be associated to a particular field in the GraphQL result,
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-- it must contain an entry with the key path that details the path of the
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-- response field which experienced the error. This allows clients to identify
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-- whether a null result is intentional or caused by a runtime error.
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data Path
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= Segment Text -- ^ Field name.
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| Index Int -- ^ List index if a field returned a list.
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deriving (Eq, Show)
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-- | @GraphQL@ error.
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data Error = Error
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{ message :: Text
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, locations :: [Location]
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, path :: [Path]
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} deriving (Eq, Show)
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-- | The server\'s response describes the result of executing the requested
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-- operation if successful, and describes any errors encountered during the
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-- request.
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data Response a = Response
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{ data' :: a
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, errors :: Seq Error
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} deriving (Eq, Show)
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-- | Each event in the underlying Source Stream triggers execution of the
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-- subscription selection set. The results of the execution generate a Response
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-- Stream.
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type ResponseEventStream m a = ConduitT () (Response a) m ()
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-- | Only exceptions that inherit from 'ResolverException' a cought by the
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-- executor.
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data ResolverException = forall e. Exception e => ResolverException e
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instance Show ResolverException where
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show (ResolverException e) = show e
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instance Exception ResolverException
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-- | Runs the given query computation, but collects the errors into an error
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-- list, which is then sent back with the data.
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runCollectErrs :: (Monad m, Serialize a)
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=> HashMap Name (Schema.Type m)
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-> CollectErrsT m a
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-> m (Response a)
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runCollectErrs types' res = do
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(dat, Resolution{..}) <- runStateT res
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$ Resolution{ errors = Seq.empty, types = types' }
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pure $ Response dat errors
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