src/Elm/Utils.hs · elk

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elk/src/Elm/Utils.hs

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1{-# OPTIONS_GHC -Wall #-}

2{-# LANGUAGE FlexibleContexts #-}

3module Elm.Utils ((|>), (<|), getAsset, run, unwrappedRun, CommandError(..)) where

5import Control.Monad.Error (MonadError, MonadIO, liftIO, throwError)

6import System.Directory (doesFileExist)

7import System.Environment (getEnv)

8import System.Exit (ExitCode(ExitSuccess, ExitFailure))

9import System.FilePath ((</>))

10import System.IO.Error (tryIOError)

11import System.Process (readProcessWithExitCode)

13import qualified Elm.Compiler.Version as Version

16{-| Forward function application `x |> f == f x`. This function is useful

17for avoiding parenthesis and writing code in a more natural way.

18-}

19(|>) :: a -> (a -> b) -> b

20x |> f = f x

23{-| Backward function application `f <| x == f x`. This function is useful for

24avoiding parenthesis.

25-}

26(<|) :: (a -> b) -> a -> b

27f <| x = f x

30infixr 0 <|

31infixl 0 |>

34-- RUN EXECUTABLES

36data CommandError

37 = MissingExe String

38 | CommandFailed String String

41{-| Run a command, throw an error if the command is not found or if something

42goes wrong.

43-}

44run :: (MonadError String m, MonadIO m) => String -> [String] -> m String

45run command args =

46 do result <- liftIO (unwrappedRun command args)

47 case result of

48 Right out -> return out

49 Left err ->

50 throwError (context (message err))

51 where

52 context msg =

53 "failure when running:" ++ concatMap (' ':) (command:args) ++ "\n" ++ msg

55 message err =

56 case err of

57 CommandFailed stderr stdout ->

58 stdout ++ stderr

59 MissingExe msg ->

60 msg

63unwrappedRun :: String -> [String] -> IO (Either CommandError String)

64unwrappedRun command args =

65 do (exitCode, stdout, stderr) <- readProcessWithExitCode command args ""

66 return $

67 case exitCode of

68 ExitSuccess -> Right stdout

69 ExitFailure code

70 | code == 127 -> Left (missingExe command) -- UNIX

71 | code == 9009 -> Left (missingExe command) -- Windows

72 | otherwise -> Left (CommandFailed stdout stderr)

75missingExe :: String -> CommandError

76missingExe command =

77 MissingExe $

78 "Could not find command '" ++ command ++ "'. Do you have it installed?\n\

79 \ Can it be run from anywhere? Is it on your PATH?"

83-- GET STATIC ASSETS

85{-| Get the absolute path to a data file. If you install with cabal it will look

86-}

87getAsset :: String -> (FilePath -> IO FilePath) -> FilePath -> IO FilePath

88getAsset project getDataFileName name =

89 do path <- getDataFileName name

90 exists <- doesFileExist path

91 if exists

92 then return path

93 else do

94 environment <- tryIOError (getEnv "ELM_HOME")

95 case environment of

96 Right env ->

97 return (env </> project </> name)

99 Left _ ->

100 fail (errorNotFound name)

101

102

103errorNotFound :: FilePath -> String

104errorNotFound name =

105 unlines

106 [ "Unable to find the ELM_HOME environment variable when searching"

107 , "for the " ++ name ++ " file."

108 , ""

109 , "If you installed Elm Platform with the Mac or Windows installer, it looks like"

110 , "ELM_HOME was not set automatically. Look up how to set environment variables"

111 , "on your platform and set ELM_HOME to the directory that contains Elm's static"