Crux.Config

This module deals with loading configurations.

Writing configurations

data Config opts

Loading options from multiple sources. First we load configuration from a file, then we consider environment variables, and finally we update using the command line flags. If there is no configuration file provided, then this is equivalent to having an empty configuration file, so the config file schema should be able to cope with missing settings.

Constructors

Config

Fields

• cfgFile :: SectionsSpec opts

  Configuration file settings (and, implicitly, defaults).

• cfgEnv :: [EnvDescr opts]

  Settings from environment variables

• cfgCmdLineFlag :: [OptDescr opts]

  Command line flags.

cfgJoin :: Config a -> Config b -> Config (a, b)

Configuration files

data SectionsSpec a

A list of section specifications used to process a whole group of key-value pairs. Multiple section specifications can be combined using this type's Applicative instance.

To create SectionsSpec values see Config.Schema.Spec

Instances

Applicative SectionsSpec

Defined in Config.Schema.Types

Methods

pure :: a -> SectionsSpec a

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

liftA2 :: (a -> b -> c) -> SectionsSpec a -> SectionsSpec b -> SectionsSpec c

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

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

Functor SectionsSpec

Defined in Config.Schema.Types

Methods

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

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

section

Arguments

:: Text

Option name

-> ValueSpec a

What type of value we expect

-> a

Default value to use if option not specified

-> Text

Documentation

-> SectionsSpec a

An option that can be configured in the file.

sectionMaybe

Arguments

:: Text

Option name

-> ValueSpec a

What type of value we expect

-> Text

Documentation

-> SectionsSpec (Maybe a)

yesOrNoSpec :: ValueSpec Bool

Specification for using atoms yes and no to represent booleans True and False respectively

stringSpec :: ValueSpec String

Specification for matching any text as a String

numSpec :: Num a => ValueSpec a

Specification for matching any integral number.

fractionalSpec :: Fractional a => ValueSpec a

Specification for matching any fractional number.

Since: config-schema-0.2.0.0

oneOrList

Arguments

:: ValueSpec a

element specification

-> ValueSpec [a]

Specification that matches either a single element or multiple elements in a list. This can be convenient for allowing the user to avoid having to specify singleton lists in the configuration file.

fileSpec :: ValueSpec FilePath

dirSpec :: ValueSpec FilePath

listSpec

Arguments

:: ValueSpec a

element specification

-> ValueSpec [a]

Primitive specification for matching a list of values each satisfying a given element specification.

Environment variables

data EnvDescr opts

How the value of an environment variable contributes to the options.

Constructors

EnvVar

Fields

• evName :: String

  Name of variable

• evDoc :: String

  Documentation

• evValue :: String -> OptSetter opts

  How it affects the options

mapEnvDescr :: (OptSetter a -> OptSetter b) -> EnvDescr a -> EnvDescr b

liftEnvDescr :: Lens' a b -> EnvDescr b -> EnvDescr a

Lifts an EnvDescr for some smaller type b into an EnvDescr with the same name and documentation, but operating over a larger type a. Useful for embedding the options of another executable within an executable with possibly additional options.

liftOptDescr :: Lens' a b -> OptDescr b -> OptDescr a

Lifts an OptDescr for some smaller type b into an OptDescr with the same name and documentation, but operating over a larger type a. Useful for embedding the options of another executable within an executable with possibly additional options.

Command line options

data OptDescr a

Describe an option.

Constructors

Option

Fields

• optShortFlags :: [Char]
• optLongFlags :: [String]
• optDescription :: String
• optArgument :: ArgDescr a

data ArgDescr a

Describe an option argumnet.

Constructors

NoArg (OptSetter a)

This option does not take an argument.

ReqArg String (String -> OptSetter a)

This option has a required argument. The string describes the type of the argument.

OptArg String (Maybe String -> OptSetter a)

This option has an optional argument. The string describes the type of the argument.

type OptSetter a = a -> Either String a

Manipulate options of type a, with support for errors.

mapOptDescr :: (OptSetter a -> OptSetter b) -> OptDescr a -> OptDescr b

mapArgDescr :: (OptSetter a -> OptSetter b) -> ArgDescr a -> ArgDescr b

parsePosNum :: (Read a, Num a, Ord a) => String -> (a -> opts -> opts) -> String -> OptSetter opts