Control.Exception.ErrorList

Documentation

class IsList elist => ErrorList elist where

Methods

addError :: Text -> elist -> elist

oneError :: Text -> elist

Instances

ErrorList EList

data EList

Constructors

EList Text [Text]

Instances

IsList EList

Eq EList

Show EList

Render EList

ErrorList EList

type Item EList = Text

throwError1 :: (ErrorList e, MonadError e m) => Text -> m a

Throws a single-message eror list.

throwErrorC :: (ErrorList e, MonadError e m) => [Text] -> m a

Concatenates a list of strings and throws them as an error.

addError1 :: (ErrorList e, MonadError e m) => Text -> e -> m a

Throws a new error with the given string added on.

addErrorC :: (ErrorList e, MonadError e m) => [Text] -> e -> m a

Throws a new error with the concatenation of the argument added on.

assert :: (ErrorList e, MonadError e m) => Bool -> Text -> m ()

If the test is false, throws an error with the given message.

assertC :: (ErrorList e, MonadError e m) => Bool -> [Text] -> m ()

Same as assert, but concatenates a text list.

wrapJust :: MonadError e m => m a -> m (Maybe a)

Wraps a successful result in a Just and a failure in a Nothing.

withHandler :: MonadError e m => (e -> m a) -> m a -> m a

Useful when the handler is more concise than the action.

ifErrorDo :: MonadError e m => m a -> m a -> m a

Specifies what to do if the given action fails.

ifErrorReturn :: MonadError e m => m a -> a -> m a

Performs an action, returning the second argument if it fails.

showError :: (Render e, Render b) => (a -> Either e b) -> a -> IO ()

Pretty-prints errors that use Either.

showError' :: (Render e, Render b) => (a -> (Either e b, c)) -> a -> IO ()

Pretty-prints errors that use Either, appearing in tuples.

errorC :: [Text] -> a

Concatenates a list of Text and makes an error out of it.

oneErrorC :: ErrorList e => [Text] -> e

Pretty-prints an error list. Considers the first item of the list to be the "main" message; subsequent messages are listed after. printErrors :: ErrorList e => e -> IO () printErrors (ErrorList err errs) = do P.putStrLn ("Error: " <> unpack err) P.mapM_ (P.putStrLn . unpack . (" " <>)) errs

Same as oneError but concatenates its argument.

firstSuccess :: (ErrorList e, MonadError e m) => Text -> [m a] -> m a

inContext :: (ErrorList e, MonadError e m) => Text -> m a -> m a

Tries something and throws an error if it fails.