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|
--------------------------------------------------------------------------------
module Language.Haskell.Stylish.Parse
( parseModule
) where
--------------------------------------------------------------------------------
import Control.Monad.Error (throwError)
import Data.Maybe (fromMaybe)
import qualified Language.Haskell.Exts.Annotated as H
--------------------------------------------------------------------------------
import Language.Haskell.Stylish.Config
import Language.Haskell.Stylish.Step
--------------------------------------------------------------------------------
-- | Filter out lines which use CPP macros
unCpp :: String -> String
unCpp = unlines . map unCpp' . lines
where
unCpp' ('#' : _) = ""
unCpp' xs = xs
--------------------------------------------------------------------------------
-- | If the given string is prefixed with an UTF-8 Byte Order Mark, drop it
-- because haskell-src-exts can't handle it.
dropBom :: String -> String
dropBom ('\xfeff' : str) = str
dropBom str = str
--------------------------------------------------------------------------------
-- | Read an extension name from a string
parseExtension :: String -> Either String H.Extension
parseExtension str = case reads str of
[(x, "")] -> return x
_ -> throwError $ "Unknown extension: " ++ str
--------------------------------------------------------------------------------
-- | Abstraction over HSE's parsing
parseModule :: Extensions -> Maybe FilePath -> String -> Either String Module
parseModule extraExts mfp string = do
-- Determine the extensions: those specified in the file and the extra ones
extraExts' <- mapM parseExtension extraExts
let fileExts = fromMaybe [] $ H.readExtensions string
exts = fileExts ++ extraExts'
-- Parsing options...
fp = fromMaybe "<unknown>" mfp
mode = H.defaultParseMode
{H.extensions = exts, H.fixities = Nothing}
-- Preprocessing
string' = dropBom $ (if H.CPP `elem` exts then unCpp else id) $ string
case H.parseModuleWithComments mode string' of
H.ParseOk md -> return md
err -> throwError $
"Language.Haskell.Stylish.Parse.parseModule: could not parse " ++
fp ++ ": " ++ show err
|
