Safe Haskell	None
Language	Haskell2010

Development.GitRev.Utils.Environment

Description

Provides utilities for querying environment variables.

Since: 0.1

Synopsis

newtype LookupEnvError = MkLookupEnvError String
envValQ :: String -> Q (Either LookupEnvError String)
runInEnvDirQ :: String -> Q a -> Q (Either LookupEnvError a)
withEnvValQ :: String -> (String -> Q a) -> Q (Either LookupEnvError a)

Documentation

newtype LookupEnvError Source #

Environment variable lookup failure. The value is the variable we attempted to look up.

Since: 0.1

Constructors

MkLookupEnvError String

Instances

Instances details

Exception LookupEnvError Source #	Since: 0.1
Instance details Defined in Development.GitRev.Utils.Environment Methods toException :: LookupEnvError -> SomeException # fromException :: SomeException -> Maybe LookupEnvError # displayException :: LookupEnvError -> String # backtraceDesired :: LookupEnvError -> Bool #
Show LookupEnvError Source #	Since: 0.1
Instance details Defined in Development.GitRev.Utils.Environment Methods showsPrec :: Int -> LookupEnvError -> ShowS # show :: LookupEnvError -> String # showList :: [LookupEnvError] -> ShowS #
Eq LookupEnvError Source #	Since: 0.1
Instance details Defined in Development.GitRev.Utils.Environment Methods (==) :: LookupEnvError -> LookupEnvError -> Bool # (/=) :: LookupEnvError -> LookupEnvError -> Bool #
Lift LookupEnvError Source #	Since: 0.1
Instance details Defined in Development.GitRev.Utils.Environment Methods lift :: Quote m => LookupEnvError -> m Exp # liftTyped :: forall (m :: Type -> Type). Quote m => LookupEnvError -> Code m LookupEnvError #

envValQ Source #

Arguments

:: String	The environment variable `k`.
-> Q (Either LookupEnvError String)	The result `v` or an error.

Performs an environment variable lookup in Q.

Examples

Expand

>>> setEnv "SOME_VAR" "val"
>>> $$(qToCode $ envValQ "SOME_VAR")
Right "val"

Since: 0.1

runInEnvDirQ Source #

Arguments

:: String	The environment variable `k` that should point to some directory `d`.
-> Q a	The `Q` action `q`.
-> Q (Either LookupEnvError a)	The result of running `q` in directory `d`.

Runs the given Q-action under the directory d pointed to by the given environment variable.

Examples

Expand

>>> import System.Directory (listDirectory)
>>> setEnv "SOME_DIR" "./src"
>>> $$(qToCode $ runInEnvDirQ "SOME_DIR" $ runIO (listDirectory "./"))
Right ["Development"]

Since: 0.1

withEnvValQ Source #

Arguments

:: String	The environment variable `k` to lookup.
-> (String -> Q a)	Function to run on `k`'s value if `k` exists.
-> Q (Either LookupEnvError a)

Runs a Q-action on the result of an environment variable, if it exists.

Examples

Expand

>>> import System.Directory (listDirectory)
>>> setEnv "SOME_DIR" "./src"
>>> $$(qToCode $ withEnvValQ "SOME_DIR" (runIO . listDirectory))
Right ["Development"]

Since: 0.1