/
Common.hs
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/
Common.hs
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{-# LANGUAGE Rank2Types #-}
module Options.Applicative.Common (
-- * Option parsers
--
-- | A 'Parser' is composed of a list of options. Several kinds of options
-- are supported:
--
-- * Flags: simple no-argument options. When a flag is encountered on the
-- command line, its value is returned.
--
-- * Options: options with an argument. An option can define a /reader/,
-- which converts its argument from String to the desired value, or throws a
-- parse error if the argument does not validate correctly.
--
-- * Arguments: positional arguments, validated in the same way as option
-- arguments.
--
-- * Commands. A command defines a completely independent sub-parser. When a
-- command is encountered, the whole command line is passed to the
-- corresponding parser.
--
Parser,
liftOpt,
showOption,
-- * Program descriptions
--
-- A 'ParserInfo' describes a command line program, used to generate a help
-- screen. Two help modes are supported: brief and full. In brief mode, only
-- an option and argument summary is displayed, while in full mode each
-- available option and command, including hidden ones, is described.
--
-- A basic 'ParserInfo' with default values for fields can be created using
-- the 'info' function.
--
-- A 'ParserPrefs' contains general preferences for all command-line
-- options, and can be built with the 'prefs' function.
ParserInfo(..),
ParserPrefs(..),
-- * Running parsers
runParserInfo,
runParserFully,
runParser,
evalParser,
-- * Low-level utilities
mapParser,
treeMapParser,
optionNames
) where
import Control.Applicative
import Control.Monad (guard, mzero, msum, when, liftM)
import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.State (StateT(..), get, put, runStateT)
import Data.List (isPrefixOf)
import Data.Maybe (maybeToList, isJust)
import Prelude
import Options.Applicative.Internal
import Options.Applicative.Types
showOption :: OptName -> String
showOption (OptLong n) = "--" ++ n
showOption (OptShort n) = '-' : [n]
optionNames :: OptReader a -> [OptName]
optionNames (OptReader names _ _) = names
optionNames (FlagReader names _) = names
optionNames _ = []
isOptionPrefix :: OptName -> OptName -> Bool
isOptionPrefix (OptShort x) (OptShort y) = x == y
isOptionPrefix (OptLong x) (OptLong y) = x `isPrefixOf` y
isOptionPrefix _ _ = False
-- | Create a parser composed of a single option.
liftOpt :: Option a -> Parser a
liftOpt = OptP
argMatches :: MonadP m => OptReader a -> String
-> Maybe (StateT Args m a)
argMatches opt arg = case opt of
ArgReader rdr -> Just . lift $
runReadM (crReader rdr) arg
CmdReader _ _ f ->
flip fmap (f arg) $ \subp -> StateT $ \args -> do
prefs <- getPrefs
let runSubparser
| prefBacktrack prefs = \i a ->
runParser (infoPolicy i) CmdStart (infoParser i) a
| otherwise = \i a
-> (,) <$> runParserInfo i a <*> pure []
enterContext arg subp *> runSubparser subp args <* exitContext
_ -> Nothing
optMatches :: MonadP m => Bool -> OptReader a -> OptWord -> Maybe (StateT Args m a)
optMatches disambiguate opt (OptWord arg1 val) = case opt of
OptReader names rdr no_arg_err -> do
guard $ has_name arg1 names
Just $ do
args <- get
let mb_args = uncons $ maybeToList val ++ args
let missing_arg = lift $ missingArgP no_arg_err (crCompleter rdr)
(arg', args') <- maybe missing_arg return mb_args
put args'
lift $ runReadM (withReadM (errorFor arg1) (crReader rdr)) arg'
FlagReader names x -> do
guard $ has_name arg1 names
Just $ do
args <- get
let val' = (\s -> '-' : s) <$> val
put $ maybeToList val' ++ args
return x
_ -> Nothing
where
errorFor name msg = "option " ++ showOption name ++ ": " ++ msg
has_name a
| disambiguate = any (isOptionPrefix a)
| otherwise = elem a
isArg :: OptReader a -> Bool
isArg (ArgReader _) = True
isArg _ = False
data OptWord = OptWord OptName (Maybe String)
parseWord :: String -> Maybe OptWord
parseWord ('-' : '-' : w) = Just $ let
(opt, arg) = case span (/= '=') w of
(_, "") -> (w, Nothing)
(w', _ : rest) -> (w', Just rest)
in OptWord (OptLong opt) arg
parseWord ('-' : w) = case w of
[] -> Nothing
(a : rest) -> Just $ let
arg = rest <$ guard (not (null rest))
in OptWord (OptShort a) arg
parseWord _ = Nothing
searchParser :: Monad m
=> (forall r . Option r -> NondetT m r)
-> Parser a -> NondetT m (Parser a)
searchParser _ (NilP _) = mzero
searchParser f (OptP opt) = liftM pure (f opt)
searchParser f (MultP p1 p2) = foldr1 (<!>)
[ do p1' <- searchParser f p1
return (p1' <*> p2)
, do p2' <- searchParser f p2
return (p1 <*> p2') ]
searchParser f (AltP p1 p2) = msum
[ searchParser f p1
, searchParser f p2 ]
searchParser f (BindP p k) = msum
[ do p' <- searchParser f p
return $ BindP p' k
, case evalParser p of
Nothing -> mzero
Just aa -> searchParser f (k aa) ]
searchOpt :: MonadP m => ParserPrefs -> OptWord -> Parser a
-> NondetT (StateT Args m) (Parser a)
searchOpt pprefs w = searchParser $ \opt -> do
let disambiguate = prefDisambiguate pprefs
&& optVisibility opt > Internal
case optMatches disambiguate (optMain opt) w of
Just matcher -> lift matcher
Nothing -> mzero
searchArg :: MonadP m => String -> Parser a
-> NondetT (StateT Args m) (Parser a)
searchArg arg = searchParser $ \opt -> do
when (isArg (optMain opt)) cut
case argMatches (optMain opt) arg of
Just matcher -> lift matcher
Nothing -> mzero
stepParser :: MonadP m => ParserPrefs -> ArgPolicy -> String
-> Parser a -> NondetT (StateT Args m) (Parser a)
stepParser _ OnlyPositionalPolicy arg p =
searchArg arg p
stepParser pprefs DefaultPositionalPolicy arg p = case parseWord arg of
Just w -> searchOpt pprefs w p <|> searchArg arg p
Nothing -> searchArg arg p
stepParser pprefs _ arg p = case parseWord arg of
Just w -> searchOpt pprefs w p
Nothing -> searchArg arg p
-- | Apply a 'Parser' to a command line, and return a result and leftover
-- arguments. This function returns an error if any parsing error occurs, or
-- if any options are missing and don't have a default value.
runParser :: MonadP m => ArgPolicy -> IsCmdStart -> Parser a -> Args -> m (a, Args)
runParser policy _ p ("--" : argt) | policy /= OnlyPositionalPolicy
= runParser OnlyPositionalPolicy CmdCont p argt
runParser policy isCmdStart p args = case args of
[] -> exitP isCmdStart p result
(arg : argt) -> do
prefs <- getPrefs
(mp', args') <- do_step prefs arg argt
case mp' of
Nothing -> hoistMaybe result <|> parseError arg
Just p' -> runParser (newPolicy arg) CmdCont p' args'
where
result = (,) <$> evalParser p <*> pure args
do_step prefs arg argt = (`runStateT` argt)
. disamb (not (prefDisambiguate prefs))
$ stepParser prefs policy arg p
newPolicy a = case policy of
NoInterspersePolicy -> if isJust (parseWord a) then NoInterspersePolicy else OnlyPositionalPolicy
x -> x
parseError :: MonadP m => String -> m a
parseError arg = errorP . ErrorMsg $ msg
where
msg = case arg of
('-':_) -> "Invalid option `" ++ arg ++ "'"
_ -> "Invalid argument `" ++ arg ++ "'"
runParserInfo :: MonadP m => ParserInfo a -> Args -> m a
runParserInfo i = runParserFully (infoPolicy i) (infoParser i)
runParserFully :: MonadP m => ArgPolicy -> Parser a -> Args -> m a
runParserFully policy p args = do
(r, args') <- runParser policy CmdStart p args
case args' of
[] -> return r
a:_ -> parseError a
-- | The default value of a 'Parser'. This function returns an error if any of
-- the options don't have a default value.
evalParser :: Parser a -> Maybe a
evalParser (NilP r) = r
evalParser (OptP _) = Nothing
evalParser (MultP p1 p2) = evalParser p1 <*> evalParser p2
evalParser (AltP p1 p2) = evalParser p1 <|> evalParser p2
evalParser (BindP p k) = evalParser p >>= evalParser . k
-- | Map a polymorphic function over all the options of a parser, and collect
-- the results in a list.
mapParser :: (forall x. OptHelpInfo -> Option x -> b)
-> Parser a -> [b]
mapParser f = flatten . treeMapParser f
where
flatten (Leaf x) = [x]
flatten (MultNode xs) = xs >>= flatten
flatten (AltNode xs) = xs >>= flatten
-- | Like 'mapParser', but collect the results in a tree structure.
treeMapParser :: (forall x . OptHelpInfo -> Option x -> b)
-> Parser a
-> OptTree b
treeMapParser g = simplify . go False False g
where
has_default :: Parser a -> Bool
has_default p = isJust (evalParser p)
go :: Bool -> Bool
-> (forall x . OptHelpInfo -> Option x -> b)
-> Parser a
-> OptTree b
go _ _ _ (NilP _) = MultNode []
go m d f (OptP opt)
| optVisibility opt > Internal
= Leaf (f (OptHelpInfo m d) opt)
| otherwise
= MultNode []
go m d f (MultP p1 p2) = MultNode [go m d f p1, go m d f p2]
go m d f (AltP p1 p2) = AltNode [go m d' f p1, go m d' f p2]
where d' = d || has_default p1 || has_default p2
go _ d f (BindP p _) = go True d f p
simplify :: OptTree a -> OptTree a
simplify (Leaf x) = Leaf x
simplify (MultNode xs) =
case concatMap (remove_mult . simplify) xs of
[x] -> x
xs' -> MultNode xs'
where
remove_mult (MultNode ts) = ts
remove_mult t = [t]
simplify (AltNode xs) =
case concatMap (remove_alt . simplify) xs of
[] -> MultNode []
[x] -> x
xs' -> AltNode xs'
where
remove_alt (AltNode ts) = ts
remove_alt (MultNode []) = []
remove_alt t = [t]