59 lines
1.6 KiB
Haskell
59 lines
1.6 KiB
Haskell
{-# LANGUAGE ConstraintKinds #-}
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{-# LANGUAGE ExistentialQuantification #-}
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{-# LANGUAGE FlexibleContexts #-}
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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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module Nix.Frames
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( NixLevel(..)
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, Frames
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, Framed
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, NixFrame(..)
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, NixException(..)
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, withFrame
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, throwError
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, module Data.Typeable
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, module Control.Exception
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)
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where
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import Control.Exception hiding ( catch
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, evaluate
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)
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import Control.Monad.Catch
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import Control.Monad.Reader
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import Data.Typeable hiding ( typeOf )
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import Nix.Utils
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data NixLevel = Fatal | Error | Warning | Info | Debug
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deriving (Ord, Eq, Bounded, Enum, Show)
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data NixFrame = NixFrame
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{ frameLevel :: NixLevel
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, frame :: SomeException
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}
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instance Show NixFrame where
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show (NixFrame level f) =
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"Nix frame at level " ++ show level ++ ": " ++ show f
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type Frames = [NixFrame]
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type Framed e m = (MonadReader e m, Has e Frames, MonadThrow m)
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newtype NixException = NixException Frames
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deriving Show
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instance Exception NixException
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withFrame
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:: forall s e m a . (Framed e m, Exception s) => NixLevel -> s -> m a -> m a
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withFrame level f = local (over hasLens (NixFrame level (toException f) :))
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throwError
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:: forall s e m a . (Framed e m, Exception s, MonadThrow m) => s -> m a
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throwError err = do
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context <- asks (view hasLens)
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traceM "Throwing error..."
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throwM $ NixException (NixFrame Error (toException err) : context)
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