Module

Options.Applicative.Builder

This module contains utility functions and combinators to create parsers for individual options.

Each parser builder takes an option modifier. A modifier can be created by composing the basic modifiers provided by this module using the 'Monoid' operations 'mempty' and 'append', or their aliases 'idm' and '<>'.

For example:

out = strOption
    ( long "output"
   <> short 'o'
   <> metavar "FILENAME" )

creates a parser for an option called output.

#subparser

subparser :: forall a. Mod CommandFields a -> Parser a

Builder for a command parser. The 'command' modifier can be used to specify individual commands.

#strArgument

strArgument :: Mod ArgumentFields String -> Parser String

Builder for a 'String' argument.

#argument

argument :: forall a. ReadM a -> Mod ArgumentFields a -> Parser a

Builder for an argument parser.

#flag

flag :: forall a. a -> a -> Mod FlagFields a -> Parser a

Builder for a flag parser.

A flag that switches from a "default value" to an "active value" when encountered. For a simple boolean value, use switch instead.

Note: Because this parser will never fail, it can not be used with combinators such as 'some' or 'many', as these combinators continue until a failure occurs. See @flag'@.

#flag'

flag' :: forall a. a -> Mod FlagFields a -> Parser a

Builder for a flag parser without a default value.

Same as 'flag', but with no default value. In particular, this flag will never parse successfully by itself.

It still makes sense to use it as part of a composite parser. For example

length <$> many (flag' () (short 't'))

is a parser that counts the number of "-t" arguments on the command line, alternatively

flag' true (long "on") <|> flag' false (long "off")

will require the user to enter '--on' or '--off' on the command line.

#switch

switch :: Mod FlagFields Boolean -> Parser Boolean

Builder for a boolean flag.

Note: Because this parser will never fail, it can not be used with combinators such as 'some' or 'many', as these combinators continue until a failure occurs. See @flag'@.

switch = flag false true

#abortOption

abortOption :: forall a. ParseError -> Mod OptionFields (a -> a) -> Parser (a -> a)

An option that always fails.

When this option is encountered, the option parser immediately aborts with the given parse error. If you simply want to output a message, use 'infoOption' instead.

#infoOption

infoOption :: forall a. String -> Mod OptionFields (a -> a) -> Parser (a -> a)

An option that always fails and displays a message.

#strOption

strOption :: Mod OptionFields String -> Parser String

Builder for an option taking a 'String' argument.

#option

option :: forall a. ReadM a -> Mod OptionFields a -> Parser a

Builder for an option using the given reader.

This is a regular option, and should always have either a long or short name specified in the modifiers (or both).

nameParser = option str ( long "name" <> short 'n' )

#short

short :: forall f a. HasName f => Char -> Mod f a

Specify a short name for an option.

#long

long :: forall f a. HasName f => String -> Mod f a

Specify a long name for an option.

#help

help :: forall a f. String -> Mod f a

Specify the help text for an option.

#helpDoc

helpDoc :: forall f a. Maybe Doc -> Mod f a

Specify the help text for an option as a 'Text.PrettyPrint.ANSI.Leijen.Doc' value.

#value

value :: forall f a. HasValue f => a -> Mod f a

Specify a default value for an option.

Note: Because this modifier means the parser will never fail, do not use it with combinators such as 'some' or 'many', as these combinators continue until a failure occurs. Careless use will thus result in a hang.

To display the default value, combine with showDefault or showDefaultWith.

#showDefaultWith

showDefaultWith :: forall f a. (a -> String) -> Mod f a

Show the default value for this option using a function.

#showDefault

showDefault :: forall f a. Show a => Mod f a

Show the default value for this option using its 'Show' instance.

#metavar

metavar :: forall f a. HasMetavar f => String -> Mod f a

Specify a metavariable for the argument.

Metavariables have no effect on the actual parser, and only serve to specify the symbolic name for an argument to be displayed in the help text.

#noArgError

noArgError :: forall a. ParseError -> Mod OptionFields a

Specify the error to display when no argument is provided to this option.

#hidden

hidden :: forall f a. Mod f a

Hide this option from the brief description.

#style

style :: forall f a. (Doc -> Doc) -> Mod f a

Apply a function to the option description in the usage text.

import Options.Applicative.Help flag' () (short 't' <> style bold)

NOTE: This builder is more flexible than its name and example allude. One of the motivating examples for its addition was to used const to completely replace the usage text of an option.

#command

command :: forall a. String -> ParserInfo a -> Mod CommandFields a

Add a command to a subparser option.

Suggested usage for multiple commands is to add them to a single subparser. e.g.

sample :: Parser Sample
sample = subparser
       ( command "hello"
         (info hello (progDesc "Print greeting"))
      <> command "goodbye"
         (info goodbye (progDesc "Say goodbye"))
       )

#commandGroup

commandGroup :: forall a. String -> Mod CommandFields a

Add a description to a group of commands.

Advanced feature for separating logical groups of commands on the parse line.

If using the same metavar for each group of commands, it may yield a more attractive usage text combined with hidden for some groups.

#completeWith

completeWith :: forall f a. HasCompleter f => Array String -> Mod f a

Add a list of possible completion values.

#action

action :: forall f a. HasCompleter f => String -> Mod f a

Add a bash completion action. Common actions include file and directory. See http://www.gnu.org/software/bash/manual/html_node/Programmable-Completion-Builtins.html#Programmable-Completion-Builtins for a complete list.

#completer

completer :: forall f a. HasCompleter f => Completer -> Mod f a

Add a completer to an argument.

A completer is a function String -> Effect String which, given a partial argument, returns all possible completions for that argument.

#idm

idm :: forall m. Monoid m => m

Trivial option modifier.

#str

str :: ReadM String

String 'Option' reader.

#int

int :: ReadM Int

Int 'Option' reader.

#number

number :: ReadM Number

Number 'Option' reader.

#boolean

boolean :: ReadM Boolean

Boolean 'Option' reader.

#maybeReader

maybeReader :: forall a. (String -> Maybe a) -> ReadM a

Convert a function producing a 'Maybe' into a reader.

#eitherReader

eitherReader :: forall a. (String -> Either String a) -> ReadM a

Convert a function producing an 'Either' into a reader.

#disabled

disabled :: forall a. ReadM a

Null 'Option' reader. All arguments will fail validation.

#InfoMod

newtype InfoMod a

Modifier for 'ParserInfo'.

Constructors

InfoMod (ParserInfo a -> ParserInfo a)

Instances

#fullDesc

fullDesc :: forall a. InfoMod a

Show a full description in the help text of this parser (i.e. options with the hidden modifier will still be displayed, unlike briefDesc).

#briefDesc

briefDesc :: forall a. InfoMod a

Only show a brief description in the help text of this parser (i.e. options with the hidden modifier will NOT be displayed, unlike fullDesc).

#headerDoc

headerDoc :: forall a. Maybe Doc -> InfoMod a

Specify a header for this parser as a 'Text.PrettyPrint.ANSI.Leijen.Doc' value.

#footerDoc

footerDoc :: forall a. Maybe Doc -> InfoMod a

Specify a footer for this parser as a 'Text.PrettyPrint.ANSI.Leijen.Doc' value.

#progDesc

progDesc :: forall a. String -> InfoMod a

Specify a short program description.

#progDescDoc

progDescDoc :: forall a. Maybe Doc -> InfoMod a

Specify a short program description as a 'Text.PrettyPrint.ANSI.Leijen.Doc' value.

#failureCode

failureCode :: forall a. ExitCode -> InfoMod a

Specify an exit code if a parse error occurs.

#noIntersperse

noIntersperse :: forall a. InfoMod a

Disable parsing of regular options after arguments. After a positional argument is parsed, all remaining options and arguments will be treated as a positional arguments. Not recommended in general as users often expect to be able to freely intersperse regular options and flags within command line options.

#forwardOptions

forwardOptions :: forall a. InfoMod a

Intersperse matched options and arguments normally, but allow unmatched options to be treated as positional arguments. This is sometimes useful if one is wrapping a third party cli tool and needs to pass options through, while also providing a handful of their own options. Not recommended in general as typos by the user may not yield a parse error and cause confusion.

#info

info :: forall a. Parser a -> InfoMod a -> ParserInfo a

Create a 'ParserInfo' given a 'Parser' and a modifier.

#PrefsMod

newtype PrefsMod

Constructors

PrefsMod (ParserPrefs -> ParserPrefs)

Instances

#multiSuffix

multiSuffix :: String -> PrefsMod

Include a suffix to attach to the metavar when multiple values can be entered.

#disambiguate

disambiguate :: PrefsMod

Turn on disambiguation.

See https://github.com/pcapriotti/optparse-applicative#disambiguation

#showHelpOnError

showHelpOnError :: PrefsMod

Show full help text on any error.

#showHelpOnEmpty

showHelpOnEmpty :: PrefsMod

Show the help text if the user enters only the program name or subcommand.

This will suppress a "Missing:" error and show the full usage instead if a user just types the name of the program.

#noBacktrack

noBacktrack :: PrefsMod

Turn off backtracking after subcommand is parsed.

#subparserInline

subparserInline :: PrefsMod

Allow full mixing of subcommand and parent arguments by inlining selected subparsers into the parent parser.

Note: When this option is used, preferences for the subparser which effect the parser behaviour (such as noIntersperse) are ignored.

#columns

columns :: Int -> PrefsMod

Set the maximum width of the generated help text.

#prefs

prefs :: PrefsMod -> ParserPrefs

Create a ParserPrefs given a modifier

#defaultPrefs

defaultPrefs :: ParserPrefs

Default preferences.

Re-exports from Options.Applicative.Builder.Internal

#OptionFields

newtype OptionFields :: forall k. k -> Typenewtype OptionFields a

Instances

#Mod

data Mod :: (Type -> Type) -> Type -> Typedata Mod f a

An option modifier.

Option modifiers are values that represent a modification of the properties of an option.

The type parameter @a@ is the pure type of the option, while @f@ is a record containing its properties (e.g. 'OptionFields' for regular options, 'FlagFields' for flags, etc...).

An option modifier consists of 3 elements:

A field modifier, of the form @f a -> f a@. These are essentially (compositions of) setters for some of the properties supported by @f@.
An optional default value and function to display it.
A property modifier, of the form @OptProperties -> OptProperties@. This is just like the field modifier, but for properties applicable to any option.

Modifiers are instances of 'Monoid', and can be composed as such.

One rarely needs to deal with modifiers directly, as most of the times it is sufficient to pass them to builders (such as 'strOption' or 'flag') to create options (see 'Options.Applicative.Builder').

Contraints are often used to ensure that the modifiers can be sensibly applied. For example, positional arguments can't be specified by long or short names, so the 'HasName' constraint is used to ensure we have a flag or option.

Instances

Monoid (Mod f a)
Semigroup (Mod f a)
@since 0.13.0.0

#FlagFields

newtype FlagFields a

Instances

Newtype (FlagFields a) _
HasName FlagFields

#CommandFields

newtype CommandFields a

Instances

Newtype (CommandFields a) _
HasMetavar CommandFields

#ArgumentFields

newtype ArgumentFields :: forall k. k -> Typenewtype ArgumentFields a

Instances

#HasCompleter

class HasCompleter :: forall k. (k -> Type) -> Constraintclass HasCompleter f

Instances

#HasMetavar

class HasMetavar :: forall k. (k -> Type) -> Constraintclass HasMetavar f

Instances

#HasName

class HasName :: forall k. (k -> Type) -> Constraintclass HasName f

Instances

HasName OptionFields
HasName FlagFields

#HasValue

class HasValue :: forall k. (k -> Type) -> Constraintclass HasValue f

Instances

#internal

internal :: forall f a. Mod f a

Hide this option from the help text

Re-exports from Options.Applicative.Types

#ReadM

newtype ReadM a

A reader is used by the 'option' and 'argument' builders to parse the data passed by the user on the command line into a data type.

The most common are 'str' which is used for 'String', there are readers for Int, Number, Boolean.

More complex types can use the 'eitherReader' or 'maybeReader' functions to pattern match or use a more expressive parser like a member of the 'Parsec' family. A newtype over 'ReaderT String Except', used by option readers.

Instances

#ParseError

data ParseError

Constructors

Instances

Semigroup ParseError

#readerError

readerError :: forall a. String -> ReadM a

Abort option reader by exiting with an error message.

#readerAbort

readerAbort :: forall a. ParseError -> ReadM a

Abort option reader by exiting with a 'ParseError'.