Control.Exception.Enclosed

The purpose of this module is to allow you to capture all exceptions originating from within the enclosed computation, while still reacting to asynchronous exceptions aimed at the calling thread.

This way, you can be sure that the function that calls, for example, catchAny, will still respond to ThreadKilled or Timeout events raised by another thread (with throwTo), while capturing all exceptions, synchronous or asynchronous, resulting from the execution of the enclosed computation.

One particular use case is to allow the safe execution of code from various libraries (which you do not control), capturing any faults that might occur, while remaining responsive to higher level events and control actions.

This library was originally developed by Michael Snoyman for the ClassyPrelude library, and was latter 'spun-off' into a separate independent package.

For a more detailed explanation of the motivation behind this functions, see:

https://www.fpcomplete.com/user/snoyberg/general-haskell/exceptions/catching-all-exceptions

and

https://groups.google.com/forum/#!topic/haskell-cafe/e9H2I-3uVJE

Exceptions

catchAny :: MonadBaseControl IO m => m a -> (SomeException -> m a) -> m a

A version of catch which is specialized for any exception. This simplifies usage as no explicit type signatures are necessary.

Note that since version 0.5.9, this function now has proper support for asynchronous exceptions, by only catching exceptions generated by the internal (enclosed) action.

Since 0.5.6

handleAny :: MonadBaseControl IO m => (SomeException -> m a) -> m a -> m a

A version of handle which is specialized for any exception. This simplifies usage as no explicit type signatures are necessary.

Note that since version 0.5.9, this function now has proper support for asynchronous exceptions, by only catching exceptions generated by the internal (enclosed) action.

Since 0.5.6

tryAny :: MonadBaseControl IO m => m a -> m (Either SomeException a)

A version of try which is specialized for any exception. This simplifies usage as no explicit type signatures are necessary.

Note that since version 0.5.9, this function now has proper support for asynchronous exceptions, by only catching exceptions generated by the internal (enclosed) action.

Since 0.5.6

catchAnyDeep :: (NFData a, MonadBaseControl IO m) => m a -> (SomeException -> m a) -> m a

An extension to catchAny which ensures that the return value is fully evaluated. See tryAnyDeep.

Since 0.5.9

handleAnyDeep :: (NFData a, MonadBaseControl IO m) => (SomeException -> m a) -> m a -> m a

flip catchAnyDeep

Since 0.5.6

tryAnyDeep :: (NFData a, MonadBaseControl IO m) => m a -> m (Either SomeException a)

An extension to tryAny which ensures that the return value is fully evaluated. In other words, if you get a Right response here, you can be confident that using it will not result in another exception.

Since 0.5.9

catchIO :: MonadBaseControl IO m => m a -> (IOException -> m a) -> m a

A version of catch which is specialized for IO exceptions. This simplifies usage as no explicit type signatures are necessary.

Since 0.5.6

handleIO :: MonadBaseControl IO m => (IOException -> m a) -> m a -> m a

A version of handle which is specialized for IO exceptions. This simplifies usage as no explicit type signatures are necessary.

Since 0.5.6

tryIO :: MonadBaseControl IO m => m a -> m (Either IOException a)

A version of try which is specialized for IO exceptions. This simplifies usage as no explicit type signatures are necessary.

Since 0.5.6

Force types

Helper functions for situations where type inferer gets confused.

asIOException :: IOException -> IOException

Since 0.5.6

asSomeException :: SomeException -> SomeException

Since 0.5.6