dhall-haskell/dhall-json/src/Dhall/DhallToYaml/Main.hs

109 lines
3.2 KiB
Haskell

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{- Shared code for the @dhall-to-yaml@ and @dhall-to-yaml-ng@ executables
-}
module Dhall.DhallToYaml.Main (main) where
import Control.Applicative (optional, (<|>))
import Control.Exception (SomeException)
import Data.ByteString (ByteString)
import Data.Monoid ((<>))
import Data.Text (Text)
import Dhall.JSON (parsePreservationAndOmission, parseConversion)
import Dhall.JSON.Yaml (Options(..), parseDocuments, parseQuoted)
import Options.Applicative (Parser, ParserInfo)
import qualified Control.Exception
import qualified Data.ByteString
import qualified Data.Text.IO as Text.IO
import qualified Data.Version
import qualified GHC.IO.Encoding
import qualified Options.Applicative as Options
import qualified System.Exit
import qualified System.IO
parseOptions :: Parser (Maybe Options)
parseOptions =
Just
<$> ( Options
<$> parseExplain
<*> Dhall.JSON.parsePreservationAndOmission
<*> parseDocuments
<*> parseQuoted
<*> Dhall.JSON.parseConversion
<*> optional parseFile
<*> optional parseOutput
)
<|> parseVersion
where
parseExplain =
Options.switch
( Options.long "explain"
<> Options.help "Explain error messages in detail"
)
parseFile =
Options.strOption
( Options.long "file"
<> Options.help "Read expression from a file instead of standard input"
<> Options.metavar "FILE"
)
parseVersion =
Options.flag'
Nothing
( Options.long "version"
<> Options.help "Display version"
)
parseOutput =
Options.strOption
( Options.long "output"
<> Options.help "Write YAML to a file instead of standard output"
<> Options.metavar "FILE"
)
parserInfo :: ParserInfo (Maybe Options)
parserInfo =
Options.info
(Options.helper <*> parseOptions)
( Options.fullDesc
<> Options.progDesc "Compile Dhall to YAML"
)
main
:: Data.Version.Version
-> (Options -> Maybe FilePath -> Text -> IO ByteString)
-> IO ()
main version dhallToYaml = do
GHC.IO.Encoding.setLocaleEncoding GHC.IO.Encoding.utf8
maybeOptions <- Options.execParser parserInfo
case maybeOptions of
Nothing -> do
putStrLn (Data.Version.showVersion version)
Just options@(Options {..}) -> do
handle $ do
contents <- case file of
Nothing -> Text.IO.getContents
Just path -> Text.IO.readFile path
let write =
case output of
Nothing -> Data.ByteString.putStr
Just file_ -> Data.ByteString.writeFile file_
write =<< dhallToYaml options file contents
handle :: IO a -> IO a
handle = Control.Exception.handle handler
where
handler :: SomeException -> IO a
handler e = do
System.IO.hPutStrLn System.IO.stderr ""
System.IO.hPrint System.IO.stderr e
System.Exit.exitFailure