Options.Applicative.Helper

Helper functions to complement Options.Applicative

To use, do something like this:

module Main where

import Options.Applicative
import Options.Applicative.Helper

data ParserResult = Result1
                  | Result2
                  | Result3
  deriving (Show)

main :: IO ()
main =
  do myResult <- helperExecParser myParser (fpDesc "Demonstration")
     doSomethingWith myResult

myParser :: Parser ParserResult
myParser =
  subconcat [ command "result1"
                      (infoHelper (pure Result1)
                                  (fpDesc "Result1"))
            , command "result2"
                      (infoHelper (pure Result2)
                                  (fpDesc "Result2"))
            , command "result3"
                      (infoHelper (pure Result3)
                                  (fpDesc "Result3"))
            ]

doSomethingWith :: ParserResult -> IO ()
doSomethingWith = print

Documentation

infoHelper :: Parser a -> InfoMod a -> ParserInfo a

Wrapper around info and helper

info (helper <*> a) ...

Instead, it's just

infoHelper a ...

altconcat :: Alternative f => [f a] -> f a

Sort of like mconcat for Alternatives

Instead of

foo <|> bar <|> baz <|> quux <|> ...

Now, it's just

altconcat [ foo
          , bar
          , baz
          , quux
          ...
          ]

subconcat :: [Mod CommandFields a] -> Parser a

altconcat . fmap subparser

Instead of

subparser (command "foo" ...)
  <|> subparser (command "bar" ...)
  <|> subparser (command "baz" ...)
  ...

Instead it's

subconcat [ command "foo" ...
          , command "bar" ...
          , command "baz" ...
          ...
          ]

fpDesc :: String -> InfoMod a

mappend fullDesc . progDesc

mconcat [ fullDesc
        , progDesc "whatever"
        ...
        ]

Now, it's just

mconcat [ fpDesc "whatever"
        ...
        ]

helperPrefs :: ParserPrefs

Preferences that I like. Using these preferences, your app will

• disambiguate shortened subcommands
• show help whenever someone makes an error.

Note that you should use this in combination with infoHelper for maximum helpfulness.

prefs helperPrefsMod

helperPrefsMod :: PrefsMod

The PrefsMod for helperPrefs so that you can add on your own preferences.

mappend disambiguate showHelpOnError

helperExecParser :: Parser a -> InfoMod a -> IO a

Wrapper around customExecParser, helperPrefs, and infoHelper

helperExecParser a b = customExecParser helperPrefs (infoHelper a b)