63 lines
2.0 KiB
Haskell
63 lines
2.0 KiB
Haskell
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{-# LANGUAGE CPP #-}
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{-# LANGUAGE OverloadedStrings #-}
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module Data.GraphQL.Error (
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parseError,
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CollectErrsT,
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addErr,
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addErrMsg,
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runCollectErrs,
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joinErrs,
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errWrap
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) where
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import qualified Data.Aeson as Aeson
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import Data.Text (Text, pack)
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import Control.Arrow ((&&&))
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#if !MIN_VERSION_base(4,8,0)
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import Control.Applicative (Applicative, pure)
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import Data.Foldable (Foldable, concatMap)
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import Prelude hiding (concatMap)
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#endif
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-- | Wraps a parse error into a list of errors.
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parseError :: Applicative f => String -> f Aeson.Value
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parseError s =
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pure $ Aeson.object [("errors", Aeson.toJSON [makeErrorMsg $ pack s])]
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-- | A wrapper for an applicative functor, for passing around error messages.
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type CollectErrsT f a = f (a,[Aeson.Value])
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-- | Takes a (wrapped) list (foldable functor) of values and errors and
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-- joins the values into a list and concatenates the errors.
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joinErrs
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:: (Functor m, Functor f, Foldable f)
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=> m (f (a,[Aeson.Value])) -> CollectErrsT m (f a)
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joinErrs = fmap $ fmap fst &&& concatMap snd
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-- | Wraps the given applicative to handle errors
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errWrap :: Functor f => f a -> f (a, [Aeson.Value])
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errWrap = fmap (flip (,) [])
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-- | Adds an error to the list of errors.
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addErr :: Functor f => Aeson.Value -> CollectErrsT f a -> CollectErrsT f a
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addErr v = (fmap . fmap) (v :)
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makeErrorMsg :: Text -> Aeson.Value
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makeErrorMsg s = Aeson.object [("message",Aeson.toJSON s)]
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-- | Convenience function for just wrapping an error message.
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addErrMsg :: Functor f => Text -> CollectErrsT f a -> CollectErrsT f a
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addErrMsg = addErr . makeErrorMsg
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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 :: Functor f => CollectErrsT f Aeson.Value -> f Aeson.Value
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runCollectErrs = fmap finalD
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where finalD (dat,errs) =
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Aeson.object $
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if null errs
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then [("data",dat)]
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else [("data",dat),("errors",Aeson.toJSON $ reverse errs)]
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