| Copyright | (c) 2021 Xy Ren |
|---|---|
| License | BSD3 |
| Maintainer | xy.r@outlook.com |
| Stability | experimental |
| Portability | non-portable (GHC only) |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
Cleff.Error
Contents
Description
Synopsis
- data Error e :: Effect where
- ThrowError :: e -> Error e m a
- CatchError :: m a -> (e -> m a) -> Error e m a
- throwError :: Error e :> es => e -> Eff es a
- catchError :: Error e :> es => Eff es a -> (e -> Eff es a) -> Eff es a
- fromEither :: Error e :> es => Either e a -> Eff es a
- fromException :: forall e es a. (Exception e, '[Error e, IOE] :>> es) => IO a -> Eff es a
- fromExceptionVia :: (Exception ex, '[Error er, IOE] :>> es) => (ex -> er) -> IO a -> Eff es a
- fromExceptionEff :: forall e es a. (Exception e, '[Error e, IOE] :>> es) => Eff es a -> Eff es a
- fromExceptionEffVia :: (Exception ex, '[Error er, IOE] :>> es) => (ex -> er) -> Eff es a -> Eff es a
- note :: Error e :> es => e -> Maybe a -> Eff es a
- catchErrorJust :: Error e :> es => (e -> Maybe b) -> Eff es a -> (b -> Eff es a) -> Eff es a
- catchErrorIf :: Error e :> es => (e -> Bool) -> Eff es a -> (e -> Eff es a) -> Eff es a
- handleError :: Error e :> es => (e -> Eff es a) -> Eff es a -> Eff es a
- handleErrorJust :: Error e :> es => (e -> Maybe b) -> (b -> Eff es a) -> Eff es a -> Eff es a
- handleErrorIf :: Error e :> es => (e -> Bool) -> (e -> Eff es a) -> Eff es a -> Eff es a
- tryError :: Error e :> es => Eff es a -> Eff es (Either e a)
- tryErrorJust :: Error e :> es => (e -> Maybe b) -> Eff es a -> Eff es (Either b a)
- runError :: forall e es a. Eff (Error e ': es) a -> Eff es (Either e a)
- mapError :: forall e e' es. Error e' :> es => (e -> e') -> Eff (Error e ': es) ~> Eff es
Effect
data Error e :: Effect where Source #
An effect capable of breaking out of current control flow by raising an exceptional value e. This effect roughly
corresponds to the MonadError typeclass and ExceptT monad transformer in mtl.
Constructors
| ThrowError :: e -> Error e m a | |
| CatchError :: m a -> (e -> m a) -> Error e m a |
Operations
fromExceptionVia :: (Exception ex, '[Error er, IOE] :>> es) => (ex -> er) -> IO a -> Eff es a Source #
Like fromException, but allows to transform the exception into another error type.
fromExceptionEff :: forall e es a. (Exception e, '[Error e, IOE] :>> es) => Eff es a -> Eff es a Source #
fromExceptionEffVia :: (Exception ex, '[Error er, IOE] :>> es) => (ex -> er) -> Eff es a -> Eff es a Source #
Like fromExceptionEff, but allows to transform the exception into another error type.
note :: Error e :> es => e -> Maybe a -> Eff es a Source #
Try to extract a value from Maybe, throw an error otherwise.
catchErrorJust :: Error e :> es => (e -> Maybe b) -> Eff es a -> (b -> Eff es a) -> Eff es a Source #
A variant of catchError that allows a predicate to choose whether to catch (Just) or rethrow (Nothing) the
error.
catchErrorIf :: Error e :> es => (e -> Bool) -> Eff es a -> (e -> Eff es a) -> Eff es a Source #
A variant of catchError that allows a predicate to choose whether to catch (True) or rethrow (False) the
error.
handleError :: Error e :> es => (e -> Eff es a) -> Eff es a -> Eff es a Source #
Flipped version of catchError.
handleErrorJust :: Error e :> es => (e -> Maybe b) -> (b -> Eff es a) -> Eff es a -> Eff es a Source #
Flipped version of catchErrorJust.
handleErrorIf :: Error e :> es => (e -> Bool) -> (e -> Eff es a) -> Eff es a -> Eff es a Source #
Flipped version of catchErrorIf.
tryError :: Error e :> es => Eff es a -> Eff es (Either e a) Source #
Runs a computation, returning a Left value if an error was thrown.
Interpretations
runError :: forall e es a. Eff (Error e ': es) a -> Eff es (Either e a) Source #
Run an Error effect.
Caveat: runError is implemented with Exceptions therefore inherits some of its unexpected behaviors.
Errors thrown in forked threads will not be directly caught by catchErrors in the parent thread. Instead it will
incur an exception, and we won't be quite able to display the details of that exception properly at that point.
Therefore please properly handle the errors in the forked threads separately.
However if you use async and wait for the action in the same effect scope (i.e. they get to be interpreted by
the same runError handler), the error will be caught in the parent thread even if you don't deal with it in the
forked thread. But if you passed the Async value out of the effect scope and waited for it elsewhere, the error
will again not be caught. The best choice is not to pass Async values around randomly.