Options.Applicative.Builder

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

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

strArgument :: Mod ArgumentFields String -> Parser String

Builder for a 'String' argument.

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

Builder for an argument parser.

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

An option that always fails and displays a message.

strOption :: Mod OptionFields String -> Parser String

Builder for an option taking a 'String' argument.

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

Specify a short name for an option.

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

Specify a long name for an option.

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

Specify the help text for an option.

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

Show the default value for this option using a function.

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

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

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 :: forall a. ParseError -> Mod OptionFields a

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

hidden :: forall f a. Mod f a

Hide this option from the brief description.

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

Add a list of possible completion values.

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 :: 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 :: forall m. Monoid m => m

Trivial option modifier.

str :: ReadM String

String 'Option' reader.

int :: ReadM Int

Int 'Option' reader.

number :: ReadM Number

Number 'Option' reader.

boolean :: ReadM Boolean

Boolean 'Option' reader.

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

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

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

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

disabled :: forall a. ReadM a

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

newtype InfoMod a

Modifier for 'ParserInfo'.

Constructors

• InfoMod (ParserInfo a -> ParserInfo a)

Instances

• Newtype (InfoMod a) _
• Monoid (InfoMod a)
• Semigroup (InfoMod a)

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 :: 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).

header :: forall a. String -> InfoMod a

Specify a header for this parser.

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

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

footer :: forall a. String -> InfoMod a

Specify a footer for this parser.

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

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

progDesc :: forall a. String -> InfoMod a

Specify a short program description.

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

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

failureCode :: forall a. ExitCode -> InfoMod a

Specify an exit code if a parse error occurs.

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

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

newtype PrefsMod

Constructors

• PrefsMod (ParserPrefs -> ParserPrefs)

Instances

• Newtype PrefsMod _
• Monoid PrefsMod
• Semigroup PrefsMod

multiSuffix :: String -> PrefsMod

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

disambiguate :: PrefsMod

Turn on disambiguation.

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

showHelpOnError :: PrefsMod

Show full help text on any error.

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 :: PrefsMod

Turn off backtracking after subcommand is parsed.

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 :: Int -> PrefsMod

Set the maximum width of the generated help text.

prefs :: PrefsMod -> ParserPrefs

Create a ParserPrefs given a modifier

defaultPrefs :: ParserPrefs

Default preferences.

newtype OptionFields a

Instances

• Newtype (OptionFields a) _
• HasName OptionFields
• HasCompleter OptionFields
• HasValue OptionFields
• HasMetavar OptionFields

data 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

newtype FlagFields a

Instances

• Newtype (FlagFields a) _
• HasName FlagFields

newtype CommandFields a

Instances

• Newtype (CommandFields a) _
• HasMetavar CommandFields

newtype ArgumentFields a

Instances

• Newtype (ArgumentFields a) _
• HasCompleter ArgumentFields
• HasValue ArgumentFields
• HasMetavar ArgumentFields

class HasCompleter f 

Instances

• HasCompleter OptionFields
• HasCompleter ArgumentFields

class HasMetavar f 

Instances

• HasMetavar OptionFields
• HasMetavar ArgumentFields
• HasMetavar CommandFields

class HasName f 

Instances

• HasName OptionFields
• HasName FlagFields

class HasValue f 

Instances

• HasValue OptionFields
• HasValue ArgumentFields

internal :: forall f a. Mod f a

Hide this option from the help text

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

• Newtype (ReadM a) _
• Functor ReadM
• Apply ReadM
• Applicative ReadM
• Alt ReadM
• Bind ReadM
• Monad ReadM
• MonadThrow String ReadM

data ParseError

Constructors

• ErrorMsg String
• InfoMsg String
• ShowHelpText
• MissingError IsCmdStart SomeParser
• ExpectsArgError String
• UnexpectedError String SomeParser

Instances

• Semigroup ParseError

readerError :: forall a. String -> ReadM a

Abort option reader by exiting with an error message.

readerAbort :: forall a. ParseError -> ReadM a

Abort option reader by exiting with a 'ParseError'.