Cabal-1.10.1.0: A framework for packaging Haskell software

Portability | portable
Maintainer | cabal-devel@haskell.org

Distribution.Simple.Command

Contents

- Command interface
  - Constructing commands
  - Associating actions with commands
  - Running commands
- Option Fields
  - Constructing Option Fields
  - Liftings & Projections
- Option Descriptions
  - OptDescr `smart` constructors

Description

This is to do with command line handling. The Cabal command line is organised into a number of named sub-commands (much like darcs). The `CommandUI` abstraction represents one of these sub-commands, with a name, description, a set of flags. Commands can be associated with actions and run. It handles some common stuff automatically, like the `--help` and command line completion flags. It is designed to allow other tools make derived commands. This feature is used heavily in `cabal-install`.

Synopsis

- data CommandUI flags = CommandUI {
  - commandName :: String
  - commandSynopsis :: String
  - commandUsage :: String -> String
  - commandDescription :: Maybe (String -> String)
  - commandDefaultFlags :: flags
  - commandOptions :: ShowOrParseArgs -> [OptionField flags]
  }
- commandShowOptions :: CommandUI flags -> flags -> [String]
- data CommandParse flags
  - = CommandHelp (String -> String)
  - | CommandList [String]
  - | CommandErrors [String]
  - | CommandReadyToGo flags
- commandParseArgs :: CommandUI flags -> Bool -> [String] -> CommandParse (flags -> flags, [String])
- data ShowOrParseArgs
  - = ShowArgs
  - | ParseArgs
- makeCommand :: String -> String -> Maybe (String -> String) -> flags -> (ShowOrParseArgs -> [OptionField flags]) -> CommandUI flags
- data Command action
- commandAddAction :: CommandUI flags -> (flags -> [String] -> action) -> Command action
- noExtraFlags :: [String] -> IO ()
- commandsRun :: CommandUI a -> [Command action] -> [String] -> CommandParse (a, CommandParse action)
- data OptionField a = OptionField {
  - optionName :: Name
  - optionDescr :: [OptDescr a]
  }
- type Name = String
- option :: SFlags -> LFlags -> Description -> get -> set -> MkOptDescr get set a -> OptionField a
- multiOption :: Name -> get -> set -> [get -> set -> OptDescr a] -> OptionField a
- liftOption :: (b -> a) -> (a -> b -> b) -> OptionField a -> OptionField b
- viewAsFieldDescr :: OptionField a -> FieldDescr a
- data OptDescr a
  - = ReqArg Description OptFlags ArgPlaceHolder (ReadE (a -> a)) (a -> [String])
  - | OptArg Description OptFlags ArgPlaceHolder (ReadE (a -> a)) (a -> a) (a -> [Maybe String])
  - | ChoiceOpt [(Description, OptFlags, a -> a, a -> Bool)]
  - | BoolOpt Description OptFlags OptFlags (Bool -> a -> a) (a -> Maybe Bool)
- type Description = String
- type SFlags = [Char]
- type LFlags = [String]
- type OptFlags = (SFlags, LFlags)
- type ArgPlaceHolder = String
- type MkOptDescr get set a = SFlags -> LFlags -> Description -> get -> set -> OptDescr a
- reqArg :: Monoid b => ArgPlaceHolder -> ReadE b -> (b -> [String]) -> MkOptDescr (a -> b) (b -> a -> a) a
- reqArg' :: Monoid b => ArgPlaceHolder -> (String -> b) -> (b -> [String]) -> MkOptDescr (a -> b) (b -> a -> a) a
- optArg :: Monoid b => ArgPlaceHolder -> ReadE b -> b -> (b -> [Maybe String]) -> MkOptDescr (a -> b) (b -> a -> a) a
- optArg' :: Monoid b => ArgPlaceHolder -> (Maybe String -> b) -> (b -> [Maybe String]) -> MkOptDescr (a -> b) (b -> a -> a) a
- noArg :: (Eq b, Monoid b) => b -> MkOptDescr (a -> b) (b -> a -> a) a
- boolOpt :: (b -> Maybe Bool) -> (Bool -> b) -> SFlags -> SFlags -> MkOptDescr (a -> b) (b -> a -> a) a
- boolOpt' :: (b -> Maybe Bool) -> (Bool -> b) -> OptFlags -> OptFlags -> MkOptDescr (a -> b) (b -> a -> a) a
- choiceOpt :: Eq b => [(b, OptFlags, Description)] -> MkOptDescr (a -> b) (b -> a -> a) a
- choiceOptFromEnum :: (Bounded b, Enum b, Show b, Eq b) => MkOptDescr (a -> b) (b -> a -> a) a

# Command interface

data CommandUI flags

Constructors

CommandUI |

Fields

commandName :: String

  The name of the command as it would be entered on the command line. For example `"build"`.

commandSynopsis :: String

  A short, one line description of the command to use in help texts.

commandUsage :: String -> String

  The useage line summary for this command

commandDescription :: Maybe (String -> String)

  Additional explanation of the command to use in help texts.

commandDefaultFlags :: flags

  Initial / empty flags

commandOptions :: ShowOrParseArgs -> [OptionField flags]

  All the Option fields for this command

commandShowOptions :: CommandUI flags -> flags -> [String]

Show flags in the standard long option command line format

data CommandParse flags

Constructors

CommandHelp (String -> String) |
CommandList [String] |
CommandErrors [String] |
CommandReadyToGo flags |

Instances

Functor CommandParse |

commandParseArgs

Arguments

:: CommandUI flags |
-> Bool | Is the command a global or subcommand?
-> [String] |
-> CommandParse (flags -> flags, [String]) |

Parse a bunch of command line arguments

## Constructing commands

data ShowOrParseArgs

Constructors

ShowArgs |
ParseArgs |

makeCommand

Arguments

:: String | name
-> String | short description
-> Maybe (String -> String) | long description
-> flags | initial/empty flags
-> (ShowOrParseArgs -> [OptionField flags]) | options
-> CommandUI flags |

Make a Command from standard `GetOpt` options.

## Associating actions with commands

data Command action

commandAddAction :: CommandUI flags -> (flags -> [String] -> action) -> Command action

noExtraFlags :: [String] -> IO ()

Utility function, many commands do not accept additional flags. This action fails with a helpful error message if the user supplies any extra.

## Running commands

commandsRun :: CommandUI a -> [Command action] -> [String] -> CommandParse (a, CommandParse action)

# Option Fields

data OptionField a

We usually have a datatype for storing configuration values, where every field stores a configuration option, and the user sets the value either via command line flags or a configuration file. An individual OptionField models such a field, and we usually build a list of options associated to a configuration datatype.

Constructors

OptionField |

Fields

optionName :: Name
optionDescr :: [OptDescr a]

type Name = String

## Constructing Option Fields

option :: SFlags -> LFlags -> Description -> get -> set -> MkOptDescr get set a -> OptionField a

Create an option taking a single OptDescr. No explicit Name is given for the Option, the name is the first LFlag given.

multiOption

Arguments

:: Name |
-> get |
-> set |
-> [get -> set -> OptDescr a] | MkOptDescr constructors partially applied to flags and description.
-> OptionField a |

Create an option taking several OptDescrs. You will have to give the flags and description individually to the OptDescr constructor.

## Liftings & Projections

liftOption :: (b -> a) -> (a -> b -> b) -> OptionField a -> OptionField b

viewAsFieldDescr :: OptionField a -> FieldDescr a

to view as a FieldDescr, we sort the list of interfaces (Req > Bool > Choice > Opt) and consider only the first one.

# Option Descriptions

data OptDescr a

An OptionField takes one or more OptDescrs, describing the command line interface for the field.

Constructors

ReqArg Description OptFlags ArgPlaceHolder (ReadE (a -> a)) (a -> [String]) |
OptArg Description OptFlags ArgPlaceHolder (ReadE (a -> a)) (a -> a) (a -> [Maybe String]) |
ChoiceOpt [(Description, OptFlags, a -> a, a -> Bool)] |
BoolOpt Description OptFlags OptFlags (Bool -> a -> a) (a -> Maybe Bool) |

type Description = String

type SFlags = [Char]

Short command line option strings

type LFlags = [String]

Long command line option strings

type OptFlags = (SFlags, LFlags)

type ArgPlaceHolder = String

## OptDescr `smart` constructors

type MkOptDescr get set a = SFlags -> LFlags -> Description -> get -> set -> OptDescr a

reqArg :: Monoid b => ArgPlaceHolder -> ReadE b -> (b -> [String]) -> MkOptDescr (a -> b) (b -> a -> a) a

Create a string-valued command line interface.

reqArg' :: Monoid b => ArgPlaceHolder -> (String -> b) -> (b -> [String]) -> MkOptDescr (a -> b) (b -> a -> a) a

(String -> a) variant of reqArg

optArg :: Monoid b => ArgPlaceHolder -> ReadE b -> b -> (b -> [Maybe String]) -> MkOptDescr (a -> b) (b -> a -> a) a

Create a string-valued command line interface with a default value.

optArg' :: Monoid b => ArgPlaceHolder -> (Maybe String -> b) -> (b -> [Maybe String]) -> MkOptDescr (a -> b) (b -> a -> a) a

(String -> a) variant of optArg

noArg :: (Eq b, Monoid b) => b -> MkOptDescr (a -> b) (b -> a -> a) a

boolOpt :: (b -> Maybe Bool) -> (Bool -> b) -> SFlags -> SFlags -> MkOptDescr (a -> b) (b -> a -> a) a

boolOpt' :: (b -> Maybe Bool) -> (Bool -> b) -> OptFlags -> OptFlags -> MkOptDescr (a -> b) (b -> a -> a) a

choiceOpt :: Eq b => [(b, OptFlags, Description)] -> MkOptDescr (a -> b) (b -> a -> a) a

create a Choice option

choiceOptFromEnum :: (Bounded b, Enum b, Show b, Eq b) => MkOptDescr (a -> b) (b -> a -> a) a

create a Choice option out of an enumeration type. As long flags, the Show output is used. As short flags, the first character which does not conflict with a previous one is used.