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{-# LANGUAGE DeriveDataTypeable, DeriveGeneric #-}
{-
Copyright (C) 2006-2015 John MacFarlane <jgm@berkeley.edu>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-}
{- |
Module : Text.Pandoc.Error
Copyright : Copyright (C) 2006-2015 John MacFarlane
License : GNU GPL, version 2 or above
Maintainer : John MacFarlane <jgm@berkeley.edu>
Stability : alpha
Portability : portable
This module provides a standard way to deal with possible errors encounted
during parsing.
-}
module Text.Pandoc.Error (PandocError(..), handleError) where
import Text.Parsec.Error
import Text.Parsec.Pos hiding (Line)
import Text.Pandoc.Compat.Except
import GHC.Generics (Generic)
import Data.Generics (Typeable)
import Control.Exception (Exception)
type Input = String
data PandocError = -- | Generic parse failure
ParseFailure String
-- | Error thrown by a Parsec parser
| ParsecError Input ParseError
deriving (Show, Typeable, Generic)
instance Exception PandocError
instance Error PandocError where
strMsg = ParseFailure
-- | An unsafe method to handle `PandocError`s.
handleError :: Either PandocError a -> a
handleError (Right r) = r
handleError (Left err) =
case err of
ParseFailure string -> error string
ParsecError input err' ->
let errPos = errorPos err'
errLine = sourceLine errPos
errColumn = sourceColumn errPos
theline = (lines input ++ [""]) !! (errLine - 1)
in error $ "\nError at " ++ show err' ++ "\n" ++
theline ++ "\n" ++ replicate (errColumn - 1) ' ' ++
"^"
|
