src/Distribution/GetOpt.hs

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.GetOpt
    -- Copyright   :  (c) Sven Panne 2002-2005
    -- License     :  BSD-style (see the file libraries/base/LICENSE)
    --
    -- Maintainer  :  libraries@haskell.org
    -- Portability :  portable
    --
    -- This is a fork of "System.Console.GetOpt" with the following changes:
    --
    -- * Treat "cabal --flag command" as "cabal command --flag" e.g.
    --   "cabal -v configure" to mean "cabal configure -v" For flags that are
    --   not recognised as global flags, pass them on to the sub-command. See
    --   the difference in 'shortOpt'.
    --
    -- * Line wrapping in the 'usageInfo' output, plus a more compact
    --   rendering of short options, and slightly less padding.
    --
    -- If you want to take on the challenge of merging this with the GetOpt
    -- from the base package then go for it!
    --
    {-# LANGUAGE TupleSections #-}
    {-# LANGUAGE NamedFieldPuns #-}
    module Distribution.GetOpt (
       -- * GetOpt
       getOpt, getOpt',
       usageInfo,
       ArgOrder(..),
       OptDescr(..),
       ArgDescr(..),

       -- * Example
       -- | See "System.Console.GetOpt" for examples
    ) where

    import Prelude ()
    import Distribution.Compat.Prelude
    import System.Console.GetOpt
             ( ArgOrder(..), OptDescr(..), ArgDescr(..) )

    data OptKind a                -- kind of cmd line arg (internal use only):
       = Opt       a                --    an option
       | UnreqOpt  String           --    an un-recognized option
       | NonOpt    String           --    a non-option
       | EndOfOpts                  --    end-of-options marker (i.e. "--")
       | OptErr    String           --    something went wrong...

    data OptHelp a = OptHelp {
          optNames :: a,
          optHelp :: String
        }

    -- | Return a string describing the usage of a command, derived from
    -- the header (first argument) and the options described by the
    -- second argument.
    usageInfo :: String                    -- header
              -> [OptDescr a]              -- option descriptors
              -> String                    -- nicely formatted decription of options
    usageInfo header optDescr = unlines (header : table)
      where
        options = flip map optDescr $ \(Option sos los ad d) ->
          OptHelp
            { optNames =
              intercalate ", " $
                map (fmtShort ad) sos ++
                map (fmtLong  ad) (take 1 los)
            , optHelp = d
            }

        maxOptNameWidth = 30
        descolWidth = 80 - (maxOptNameWidth + 3)

        table :: [String]
        table = do
          OptHelp{optNames, optHelp} <- options
          let wrappedHelp = wrapText descolWidth optHelp
          if length optNames >= maxOptNameWidth
            then [" " ++ optNames] ++
                 renderColumns [] wrappedHelp
            else renderColumns [optNames] wrappedHelp

        renderColumns :: [String] -> [String] -> [String]
        renderColumns xs ys = do
          (x, y) <- zipDefault "" "" xs ys
          return $ " " ++ padTo maxOptNameWidth x ++ " " ++ y

        padTo n x  = take n (x ++ repeat ' ')

    zipDefault :: a -> b -> [a] -> [b] -> [(a,b)]
    zipDefault _  _  []     []     = []
    zipDefault _  bd (a:as) []     = (a,bd) : map (,bd) as
    zipDefault ad _  []     (b:bs) = (ad,b) : map (ad,) bs
    zipDefault ad bd (a:as) (b:bs) = (a,b)  : zipDefault ad bd as bs

    fmtShort :: ArgDescr a -> Char -> String
    fmtShort (NoArg  _   ) so = "-" ++ [so]
    fmtShort (ReqArg _  _) so = "-" ++ [so]
    fmtShort (OptArg _  _) so = "-" ++ [so]
      -- unlike upstream GetOpt we omit the arg name for short options

    fmtLong :: ArgDescr a -> String -> String
    fmtLong (NoArg  _   ) lo = "--" ++ lo
    fmtLong (ReqArg _ ad) lo = "--" ++ lo ++ "=" ++ ad
    fmtLong (OptArg _ ad) lo = "--" ++ lo ++ "[=" ++ ad ++ "]"

    wrapText :: Int -> String -> [String]
    wrapText width = map unwords . wrap 0 [] . words
      where wrap :: Int -> [String] -> [String] -> [[String]]
            wrap 0   []   (w:ws)
              | length w + 1 > width
              = wrap (length w) [w] ws
            wrap col line (w:ws)
              | col + length w + 1 > width
              = reverse line : wrap 0 [] (w:ws)
            wrap col line (w:ws)
              = let col' = col + length w + 1
                 in wrap col' (w:line) ws
            wrap _ []   [] = []
            wrap _ line [] = [reverse line]

    {-|
    Process the command-line, and return the list of values that matched
    (and those that didn\'t). The arguments are:

    * The order requirements (see 'ArgOrder')

    * The option descriptions (see 'OptDescr')

    * The actual command line arguments (presumably got from
      'System.Environment.getArgs').

    'getOpt' returns a triple consisting of the option arguments, a list
    of non-options, and a list of error messages.
    -}
    getOpt :: ArgOrder a                   -- non-option handling
           -> [OptDescr a]                 -- option descriptors
           -> [String]                     -- the command-line arguments
           -> ([a],[String],[String])      -- (options,non-options,error messages)
    getOpt ordering optDescr args = (os,xs,es ++ map errUnrec us)
       where (os,xs,us,es) = getOpt' ordering optDescr args

    {-|
    This is almost the same as 'getOpt', but returns a quadruple
    consisting of the option arguments, a list of non-options, a list of
    unrecognized options, and a list of error messages.
    -}
    getOpt' :: ArgOrder a                         -- non-option handling
            -> [OptDescr a]                       -- option descriptors
            -> [String]                           -- the command-line arguments
            -> ([a],[String], [String] ,[String]) -- (options,non-options,unrecognized,error messages)
    getOpt' _        _        []         =  ([],[],[],[])
    getOpt' ordering optDescr (arg:args) = procNextOpt opt ordering
       where procNextOpt (Opt o)      _                 = (o:os,xs,us,es)
             procNextOpt (UnreqOpt u) _                 = (os,xs,u:us,es)
             procNextOpt (NonOpt x)   RequireOrder      = ([],x:rest,[],[])
             procNextOpt (NonOpt x)   Permute           = (os,x:xs,us,es)
             procNextOpt (NonOpt x)   (ReturnInOrder f) = (f x :os, xs,us,es)
             procNextOpt EndOfOpts    RequireOrder      = ([],rest,[],[])
             procNextOpt EndOfOpts    Permute           = ([],rest,[],[])
             procNextOpt EndOfOpts    (ReturnInOrder f) = (map f rest,[],[],[])
             procNextOpt (OptErr e)   _                 = (os,xs,us,e:es)

             (opt,rest) = getNext arg args optDescr
             (os,xs,us,es) = getOpt' ordering optDescr rest

    -- take a look at the next cmd line arg and decide what to do with it
    getNext :: String -> [String] -> [OptDescr a] -> (OptKind a,[String])
    getNext ('-':'-':[]) rest _        = (EndOfOpts,rest)
    getNext ('-':'-':xs) rest optDescr = longOpt xs rest optDescr
    getNext ('-': x :xs) rest optDescr = shortOpt x xs rest optDescr
    getNext a            rest _        = (NonOpt a,rest)

    -- handle long option
    longOpt :: String -> [String] -> [OptDescr a] -> (OptKind a,[String])
    longOpt ls rs optDescr = long ads arg rs
       where (opt,arg) = break (=='=') ls
             getWith p = [ o  | o@(Option _ xs _ _) <- optDescr
                              , isJust (find (p opt) xs)]
             exact     = getWith (==)
             options   = if null exact then getWith isPrefixOf else exact
             ads       = [ ad | Option _ _ ad _ <- options ]
             optStr    = "--" ++ opt

             long (_:_:_)      _        rest     = (errAmbig options optStr,rest)
             long [NoArg  a  ] []       rest     = (Opt a,rest)
             long [NoArg  _  ] ('=':_)  rest     = (errNoArg optStr,rest)
             long [ReqArg _ d] []       []       = (errReq d optStr,[])
             long [ReqArg f _] []       (r:rest) = (Opt (f r),rest)
             long [ReqArg f _] ('=':xs) rest     = (Opt (f xs),rest)
             long [OptArg f _] []       rest     = (Opt (f Nothing),rest)
             long [OptArg f _] ('=':xs) rest     = (Opt (f (Just xs)),rest)
             long _            _        rest     = (UnreqOpt ("--"++ls),rest)

    -- handle short option
    shortOpt :: Char -> String -> [String] -> [OptDescr a] -> (OptKind a,[String])
    shortOpt y ys rs optDescr = short ads ys rs
      where options = [ o  | o@(Option ss _ _ _) <- optDescr, s <- ss, y == s ]
            ads     = [ ad | Option _ _ ad _ <- options ]
            optStr  = '-':[y]

            short (_:_:_)        _  rest     = (errAmbig options optStr,rest)
            short (NoArg  a  :_) [] rest     = (Opt a,rest)
            short (NoArg  a  :_) xs rest     = (Opt a,('-':xs):rest)
            short (ReqArg _ d:_) [] []       = (errReq d optStr,[])
            short (ReqArg f _:_) [] (r:rest) = (Opt (f r),rest)
            short (ReqArg f _:_) xs rest     = (Opt (f xs),rest)
            short (OptArg f _:_) [] rest     = (Opt (f Nothing),rest)
            short (OptArg f _:_) xs rest     = (Opt (f (Just xs)),rest)
            short []             [] rest     = (UnreqOpt optStr,rest)
            short []             xs rest     = (UnreqOpt (optStr++xs),rest)
            -- This is different vs upstream = (UnreqOpt optStr,('-':xs):rest)
            -- Apparently this was part of the change so that flags that are
            -- not recognised as global flags are passed on to the sub-command.
            -- But why was no equivalent change required for longOpt? So could
            -- this change go upstream?

    -- miscellaneous error formatting

    errAmbig :: [OptDescr a] -> String -> OptKind a
    errAmbig ods optStr = OptErr (usageInfo header ods)
       where header = "option `" ++ optStr ++ "' is ambiguous; could be one of:"

    errReq :: String -> String -> OptKind a
    errReq d optStr = OptErr ("option `" ++ optStr ++ "' requires an argument " ++ d ++ "\n")

    errUnrec :: String -> String
    errUnrec optStr = "unrecognized option `" ++ optStr ++ "'\n"

    errNoArg :: String -> OptKind a
    errNoArg optStr = OptErr ("option `" ++ optStr ++ "' doesn't allow an argument\n")