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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,
-- * 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.
ParserInfo(..),
-- * Running parsers
runParser,
runParserFully,
evalParser,
-- * Low-level utilities
mapParser,
treeMapParser,
optionNames
) where
import Control.Applicative (pure, (<*>), (<$>), (<|>), empty)
import Control.Monad (guard, msum)
import Data.List (isPrefixOf)
import Data.Maybe (maybeToList, isJust)
import Data.Monoid (Monoid(..))
import Options.Applicative.Internal
import Options.Applicative.Types
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
data MatchResult
= NoMatch
| Match (Maybe String)
instance Monoid MatchResult where
mempty = NoMatch
mappend m@(Match _) _ = m
mappend _ m = m
type Matcher m a = [String] -> m (a, [String])
optMatches :: MonadP m => Bool -> OptReader a -> String -> Maybe (Matcher m a)
optMatches disambiguate opt arg = case opt of
OptReader names rdr no_arg_err -> do
(arg1, val) <- parsed
guard $ has_name arg1 names
return $ \args -> do
let mb_args = uncons $ maybeToList val ++ args
let missing_arg = missingArgP no_arg_err (crCompleter rdr)
(arg', args') <- maybe missing_arg return mb_args
r <- liftEither (crReader rdr arg')
return (r, args')
FlagReader names x -> do
(arg1, Nothing) <- parsed
guard $ has_name arg1 names
return $ \args -> return (x, args)
ArgReader rdr -> do
result <- crReader rdr arg
return $ \args -> return (result, args)
CmdReader _ f ->
flip fmap (f arg) $ \subp args -> do
setContext (Just arg) subp
prefs <- getPrefs
let runSubparser
| prefBacktrack prefs = runParser
| otherwise = \p a
-> (,) <$> runParserFully p a <*> pure []
runSubparser (infoParser subp) args
where
parsed =
case arg of
'-' : '-' : arg1 ->
Just $
case span (/= '=') arg1 of
(_, "") -> (OptLong arg1, Nothing)
(arg1', _ : rest) -> (OptLong arg1', Just rest)
'-' : arg1 ->
case arg1 of
[] -> Nothing
(a : rest) -> Just (OptShort a, if null rest then Nothing else Just rest)
_ -> Nothing
has_name a
| disambiguate = any (isOptionPrefix a)
| otherwise = elem a
stepParser :: MonadP m => ParserPrefs -> Parser a -> String -> [String] -> [m (Parser a, [String])]
stepParser _ (NilP _) _ _ = []
stepParser prefs (OptP opt) arg args =
case optMatches disambiguate (optMain opt) arg of
Just matcher -> pure $ do
(r, args') <- matcher args
return (pure r, args')
Nothing -> empty
where
disambiguate = prefDisambiguate prefs
&& optVisibility opt > Internal
stepParser prefs (MultP p1 p2) arg args = msum
[ flip map (stepParser prefs p1 arg args) $ \m ->
do (p1', args') <- m
return (p1' <*> p2, args')
, flip map (stepParser prefs p2 arg args) $ \m ->
do (p2', args') <- m
return (p1 <*> p2', args') ]
stepParser prefs (AltP p1 p2) arg args = msum
[ stepParser prefs p1 arg args
, stepParser prefs p2 arg args ]
stepParser prefs (BindP p k) arg args =
flip map (stepParser prefs p arg args) $ \m -> do
(p', args') <- m
x <- liftMaybe $ evalParser p'
return (k x, args')
-- | 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 => Parser a -> [String] -> m (a, [String])
runParser p args = case args of
[] -> exitP p result
(arg : argt) -> do
prefs <- getPrefs
x <- tryP $ do_step prefs arg argt
case x of
Left e -> case (result, e) of
(Just r, ErrorMsg _) -> return r
_ -> errorP e
Right (p', args') -> runParser p' args'
where
result = (,) <$> evalParser p <*> pure args
do_step prefs arg argt
| prefDisambiguate prefs
= case parses of
[m] -> m
_ -> empty
| otherwise
= case parses of
[] -> parseError arg
(m : _) -> m
where parses = stepParser prefs p arg argt
parseError :: MonadP m => String -> m a
parseError arg = errorP . ErrorMsg $ msg
where
msg = case arg of
('-':_) -> "Invalid option `" ++ arg ++ "'"
_ -> "Invalid argument `" ++ arg ++ "'"
runParserFully :: MonadP m => Parser a -> [String] -> m a
runParserFully p args = do
(r, args') <- runParser p args
guard $ null args'
return r
-- | 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]