Options.Applicative.Extra

Extra parser utilities

This module contains high-level functions to run parsers.

helper :: Parser (a -> a)

A hidden "helper" option which always fails.

A common usage pattern is to apply this applicatively when creating a ParserInfo

opts :: ParserInfo Sample
opts = info (sample <**> helper) mempty

hsubparser :: Mod CommandFields a -> Parser a

Builder for a command parser with a "helper" option attached. Used in the same way as subparser, but includes a "--help|-h" inside the subcommand.

execParser :: ParserInfo a -> IO a

Run a program description.

Parse command line arguments. Display help text and exit if any parse error occurs.

execParserMaybe :: ParserInfo a -> [String] -> Maybe a

Deprecated: Use execParserPure together with getParseResult instead

Run a program description in pure code.

This function behaves like execParser, but can be called from pure code. Note that, in case of errors, no message is displayed, and this function simply returns Nothing.

If you need to keep track of error messages, use execParserPure instead.

customExecParser :: ParserPrefs -> ParserInfo a -> IO a

Run a program description with custom preferences.

customExecParserMaybe :: ParserPrefs -> ParserInfo a -> [String] -> Maybe a

Deprecated: Use execParserPure together with getParseResult instead

Run a program description with custom preferences in pure code.

See execParserMaybe for details.

execParserPure

Arguments

:: ParserPrefs

Global preferences for this parser

-> ParserInfo a

Description of the program to run

-> [String]

Program arguments

-> ParserResult a

The most general way to run a program description in pure code.

getParseResult :: ParserResult a -> Maybe a

Extract the actual result from a ParserResult value.

This function returns Nothing in case of errors. Possible error messages or completion actions are simply discarded.

If you want to display error messages and invoke completion actions appropriately, use handleParseResult instead.

handleParseResult :: ParserResult a -> IO a

Handle ParserResult.

parserFailure :: ParserPrefs -> ParserInfo a -> ParseError -> [Context] -> ParserFailure ParserHelp

Generate a ParserFailure from a ParseError in a given Context.

This function can be used, for example, to show the help text for a parser:

handleParseResult . Failure $ parserFailure pprefs pinfo ShowHelpText mempty

renderFailure :: ParserFailure ParserHelp -> String -> (String, ExitCode)

newtype ParserFailure h

Constructors

ParserFailure

Fields

• execFailure :: String -> (h, ExitCode, Int)

Instances

Functor ParserFailure

Methods

fmap :: (a -> b) -> ParserFailure a -> ParserFailure b

(<$) :: a -> ParserFailure b -> ParserFailure a

Show h => Show (ParserFailure h)

Methods

showsPrec :: Int -> ParserFailure h -> ShowS

show :: ParserFailure h -> String

showList :: [ParserFailure h] -> ShowS

overFailure :: (ParserHelp -> ParserHelp) -> ParserResult a -> ParserResult a

data ParserResult a

Result of execParserPure.

Constructors

Success a

Failure (ParserFailure ParserHelp)

CompletionInvoked CompletionResult

Instances

Monad ParserResult

Methods

(>>=) :: ParserResult a -> (a -> ParserResult b) -> ParserResult b

(>>) :: ParserResult a -> ParserResult b -> ParserResult b

return :: a -> ParserResult a

fail :: String -> ParserResult a

Functor ParserResult

Methods

fmap :: (a -> b) -> ParserResult a -> ParserResult b

(<$) :: a -> ParserResult b -> ParserResult a

Applicative ParserResult

Methods

pure :: a -> ParserResult a

(<*>) :: ParserResult (a -> b) -> ParserResult a -> ParserResult b

(*>) :: ParserResult a -> ParserResult b -> ParserResult b

(<*) :: ParserResult a -> ParserResult b -> ParserResult a

Show a => Show (ParserResult a)

Methods

showsPrec :: Int -> ParserResult a -> ShowS

show :: ParserResult a -> String

showList :: [ParserResult a] -> ShowS

data ParserPrefs

Global preferences for a top-level Parser.

Constructors

ParserPrefs

Fields

• prefMultiSuffix :: String

  metavar suffix for multiple options

• prefDisambiguate :: Bool

  automatically disambiguate abbreviations (default: False)

• prefShowHelpOnError :: Bool

  always show help text on parse errors (default: False)

• prefShowHelpOnEmpty :: Bool

  show the help text for a command or subcommand if it fails with no input (default: False)

• prefBacktrack :: Bool

  backtrack to parent parser when a subcommand fails (default: True)

• prefColumns :: Int

  number of columns in the terminal, used to format the help page (default: 80)

Instances

Eq ParserPrefs

Methods

(==) :: ParserPrefs -> ParserPrefs -> Bool

(/=) :: ParserPrefs -> ParserPrefs -> Bool

Show ParserPrefs

Methods

showsPrec :: Int -> ParserPrefs -> ShowS

show :: ParserPrefs -> String

showList :: [ParserPrefs] -> ShowS

newtype CompletionResult

Constructors

CompletionResult

Fields

• execCompletion :: String -> IO String

Instances

Show CompletionResult

Methods

showsPrec :: Int -> CompletionResult -> ShowS

show :: CompletionResult -> String

showList :: [CompletionResult] -> ShowS