Magicbane.Config

Utility functions and reexports for System.Envy, an environment variable config reader.

Documentation

showEnv :: IO ()

Display all environment variables, for convenience

unsetEnvironment' :: ToEnv a => a -> IO (Either String ())

Unset Environment using a value of class ToEnv

unsetEnvironment :: EnvList a -> IO (Either String ())

Unset Environment from a ToEnv constrained type

setEnvironment' :: ToEnv a => a -> IO (Either String ())

Set environment directly using a value of class ToEnv

setEnvironment :: EnvList a -> IO (Either String ())

Set environment via a ToEnv constrained type

decodeEnv :: FromEnv a => IO (Either String a)

Environment retrieval with failure info

makeEnv :: [EnvVar] -> EnvList a

Smart constructor, environment creation helper.

gFromEnvCustom :: (DefConfig a, Generic a, GFromEnv (Rep a)) => Option -> Parser a

Meant for specifying a custom Option for environment retrieval

instance FromEnv PGConfig where
  fromEnv = gFromEnvCustom Option { dropPrefixCount = 8, customPrefix = "PG" }

envMaybe

Arguments

:: Var a

=> String

Key to look up.

-> Parser (Maybe a)

Return Nothing if variable isn't set.

Environment variable getter returning Maybe

env

Arguments

:: Var a

=> String

Key to look up.

-> Parser a

Return a value of this type or throw an error.

Environment variable getter. Fails if the variable is not set or fails to parse.

runEnv :: Parser a -> IO (Either String a)

For use with Generics, no FromEnv typeclass necessary

getPgConfig :: IO (Either String ConnectInfo)
getPgConfig = runEnv $ gFromEnvCustom defOption

newtype Parser a

Parser Monad for environment variable retrieval

Constructors

Parser

Fields

• runParser :: ExceptT String IO a

Instances

Monad Parser

Defined in System.Envy

Methods

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

(>>) :: Parser a -> Parser b -> Parser b

return :: a -> Parser a

fail :: String -> Parser a

Functor Parser

Defined in System.Envy

Methods

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

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

Applicative Parser

Defined in System.Envy

Methods

pure :: a -> Parser a

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

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

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

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

Alternative Parser

Defined in System.Envy

Methods

empty :: Parser a

(<|>) :: Parser a -> Parser a -> Parser a

some :: Parser a -> Parser [a]

many :: Parser a -> Parser [a]

MonadPlus Parser

Defined in System.Envy

Methods

mzero :: Parser a

mplus :: Parser a -> Parser a -> Parser a

MonadIO Parser

Defined in System.Envy

Methods

liftIO :: IO a -> Parser a

MonadError String Parser

Defined in System.Envy

Methods

throwError :: String -> Parser a

catchError :: Parser a -> (String -> Parser a) -> Parser a

class FromEnv a where

FromEnv Typeclass w/ Generic default implementation

Methods

fromEnv :: Parser a

class DefConfig a where

Type class for objects which have a default configuration.

Minimal complete definition

defConfig

Methods

defConfig :: a

data Option

For customizing environment variable generation

Constructors

Option

Fields

• dropPrefixCount :: Int

  Applied first

• customPrefix :: String

  Converted toUpper

Instances

Show Option

Defined in System.Envy

Methods

showsPrec :: Int -> Option -> ShowS

show :: Option -> String

showList :: [Option] -> ShowS

class ToEnv a where

Type class for objects which can be converted to a set of environment variable settings.

Minimal complete definition

toEnv

Methods

toEnv :: a -> EnvList a

Convert an object into a list of environment variable settings.

data EnvList a

List of environment variables. Captures a "phantom type" which allows the type checker to detect the proper implementation of toEnv to use.

Instances

Show (EnvList a)

Defined in System.Envy

Methods

showsPrec :: Int -> EnvList a -> ShowS

show :: EnvList a -> String

showList :: [EnvList a] -> ShowS

class Typeable a => Var a where

Class for converting to / from an environment variable

Minimal complete definition

toVar, fromVar

Methods

toVar :: a -> String

Convert a value into an environment variable.

fromVar :: String -> Maybe a

Parse an environment variable.

Instances

Var Bool

Defined in System.Envy

Methods

toVar :: Bool -> String

fromVar :: String -> Maybe Bool

Var Double

Defined in System.Envy

Methods

toVar :: Double -> String

fromVar :: String -> Maybe Double

Var Int

Defined in System.Envy

Methods

toVar :: Int -> String

fromVar :: String -> Maybe Int

Var Int8

Defined in System.Envy

Methods

toVar :: Int8 -> String

fromVar :: String -> Maybe Int8

Var Int16

Defined in System.Envy

Methods

toVar :: Int16 -> String

fromVar :: String -> Maybe Int16

Var Int32

Defined in System.Envy

Methods

toVar :: Int32 -> String

fromVar :: String -> Maybe Int32

Var Int64

Defined in System.Envy

Methods

toVar :: Int64 -> String

fromVar :: String -> Maybe Int64

Var Integer

Defined in System.Envy

Methods

toVar :: Integer -> String

fromVar :: String -> Maybe Integer

Var Word8

Defined in System.Envy

Methods

toVar :: Word8 -> String

fromVar :: String -> Maybe Word8

Var Word16

Defined in System.Envy

Methods

toVar :: Word16 -> String

fromVar :: String -> Maybe Word16

Var Word32

Defined in System.Envy

Methods

toVar :: Word32 -> String

fromVar :: String -> Maybe Word32

Var Word64

Defined in System.Envy

Methods

toVar :: Word64 -> String

fromVar :: String -> Maybe Word64

Var ()

Defined in System.Envy

Methods

toVar :: () -> String

fromVar :: String -> Maybe ()

Var String

Defined in System.Envy

Methods

toVar :: String -> String

fromVar :: String -> Maybe String

Var ByteString

Defined in System.Envy

Methods

toVar :: ByteString -> String

fromVar :: String -> Maybe ByteString

Var ByteString

Defined in System.Envy

Methods

toVar :: ByteString -> String

fromVar :: String -> Maybe ByteString

Var Text

Defined in System.Envy

Methods

toVar :: Text -> String

fromVar :: String -> Maybe Text

Var UTCTime

Defined in System.Envy

Methods

toVar :: UTCTime -> String

fromVar :: String -> Maybe UTCTime

Var Text

Defined in System.Envy

Methods

toVar :: Text -> String

fromVar :: String -> Maybe Text

Var Day

Defined in System.Envy

Methods

toVar :: Day -> String

fromVar :: String -> Maybe Day

Var a => Var (Maybe a)

Defined in System.Envy

Methods

toVar :: Maybe a -> String

fromVar :: String -> Maybe (Maybe a)

decodeEnvy :: FromEnv a => IO (Maybe a)

withEnvConfig :: FromEnv α => (α -> IO ()) -> IO ()

Reads an Envy configuration from the env variables and launches the given action if successful. (Does environment variable reading ever fail in practice? Probably not.)