src/Build/Artifact.hs · elk

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elk/src/Build/Artifact.hs

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1{-# OPTIONS_GHC -W #-}

2{-# LANGUAGE FlexibleContexts #-}

3module Build.Artifact (read) where

5import Prelude hiding (read)

6import Control.Monad.Error (MonadError, throwError, MonadIO, liftIO)

7import qualified Data.ByteString.Lazy as LBS

8import qualified Data.Binary as Binary

9import System.Directory (doesFileExist)

12read :: (MonadIO m, MonadError String m, Binary.Binary a) => FilePath -> m a

13read filePath =

14 do exists <- liftIO (doesFileExist filePath)

15 if exists then decode else throwError notFound

16 where

17 decode =

18 do bytes <- liftIO (LBS.readFile filePath)

19 case Binary.decodeOrFail bytes of

20 Right (_, _, binaryInfo) -> return binaryInfo

21 Left (_, _, _) -> throwError corrupted

23 corrupted =

24 concat

25 [ "Error reading build artifact ", filePath, "\n"

26 , " The file was generated by a previous build and may be outdated or corrupt.\n"

27 , " Please remove the file and try again."

28 ]

30 notFound =

31 "Unable to find file " ++ filePath ++ " for deserialization!"