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{- optparse-applicative additions
-
- Copyright 2015 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
module Utility.OptParse where
import Options.Applicative
import Data.Monoid
import Prelude
-- | A switch that can be enabled using --foo and disabled using --no-foo.
--
-- The option modifier is applied to only the option that is *not* enabled
-- by default. For example:
--
-- > invertableSwitch "recursive" True (help "do not recurse into directories")
--
-- This example makes --recursive enabled by default, so
-- the help is shown only for --no-recursive.
invertableSwitch
:: String -- ^ long option
-> Bool -- ^ is switch enabled by default?
-> Mod FlagFields Bool -- ^ option modifier
-> Parser Bool
invertableSwitch longopt defv optmod = invertableSwitch' longopt defv
(if defv then mempty else optmod)
(if defv then optmod else mempty)
-- | Allows providing option modifiers for both --foo and --no-foo.
invertableSwitch'
:: String -- ^ long option (eg "foo")
-> Bool -- ^ is switch enabled by default?
-> Mod FlagFields Bool -- ^ option modifier for --foo
-> Mod FlagFields Bool -- ^ option modifier for --no-foo
-> Parser Bool
invertableSwitch' longopt defv enmod dismod = collapse <$> many
( flag' True (enmod <> long longopt)
<|> flag' False (dismod <> long nolongopt)
)
where
nolongopt = "no-" ++ longopt
collapse [] = defv
collapse l = last l
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