Env.Internal.Error

This module contains an extensible error infrastructure.

Each kind of errors gets a separate type class which encodes a Prism (roughly a getter and a constructor). The Readers, then, have the constraints for precisely the set of errors they can return.

Documentation

data Error

The type of errors returned by envparse's Readers. These fall into 3 categories:

• Variables that are unset in the environment.
• Variables whose value is empty.
• Variables whose value cannot be parsed using the Read instance.

Constructors

UnsetError

EmptyError

UnreadError String

Instances

Eq Error

Show Error

AsUnread Error

AsEmpty Error

AsUnset Error

class AsUnset e where

The class of types that contain and can be constructed from the error returned from parsing unset variables.

Methods

unset :: e

tryUnset :: e -> Maybe ()

Instances

AsUnset Error

class AsEmpty e where

The class of types that contain and can be constructed from the error returned from parsing variables whose value is empty.

Methods

empty :: e

tryEmpty :: e -> Maybe ()

Instances

AsEmpty Error

class AsUnread e where

The class of types that contain and can be constructed from the error returned from parsing variable whose value cannot be parsed using the Read instance.

Methods

unread :: String -> e

tryUnread :: e -> Maybe String

Instances

AsUnread Error