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--------------------------------------------------------------------------------
module Language.Haskell.Stylish.Parse
( parseModule
) where
--------------------------------------------------------------------------------
import Control.Monad.Error (throwError)
import Data.Maybe (fromMaybe, listToMaybe)
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 . go False . lines
where
go _ [] = []
go isMultiline (x : xs) =
let isCpp = isMultiline || listToMaybe x == Just '#'
nextMultiline = isCpp && not (null x) && last x == '\\'
in (if isCpp then "" else x) : go nextMultiline 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
--------------------------------------------------------------------------------
-- | 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
let noBom = dropBom string
extraExts' = map H.classifyExtension extraExts
(lang, fileExts) = fromMaybe (Nothing, []) $ H.readExtensions noBom
exts = fileExts ++ extraExts'
-- Parsing options...
fp = fromMaybe "<unknown>" mfp
mode = H.defaultParseMode
{ H.extensions = exts
, H.fixities = Nothing
, H.baseLanguage = case lang of
Nothing -> H.baseLanguage H.defaultParseMode
Just l -> l
}
-- Preprocessing
noCpp =
if H.EnableExtension H.CPP `elem` exts then unCpp noBom else noBom
case H.parseModuleWithComments mode noCpp of
H.ParseOk md -> return md
err -> throwError $
"Language.Haskell.Stylish.Parse.parseModule: could not parse " ++
fp ++ ": " ++ show err
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