How would one use dejafu with safe-exceptions or unliftio?

[robinp]

Those libs are getting some traction. I wonder if it is possible to run dejafu against those? Also, would it be able to take into account the different behavior of exception handling primitives (regarding using uninterruptibleMask in cleanup for example)?

[barrucadu]

safe-exceptions uses the typeclasses from the exceptions library, which dejafu also uses, so I think all the safe-exceptions functionality will just work, except for:

• throwTo - because it uses Control.Exception.throwTo
• catching exceptions thrown by assert or impureThrow - because they use primitive IO exception mechanisms

Though if you've got any examples where dejafu doesn't work, I'd be interested to see them.

unliftio is trickier, because its whole idea is to run things in IO, eg UnliftIO.Concurrent.forkIO is

forkIO :: MonadUnliftIO m => m () -> m ThreadId
forkIO m = withRunInIO $ \run -> C.forkIO $ run m

Where that C is Control.Concurrent. dejafu is based on abstracting over IO, because we can't inspect IO actions. I don't have a good answer for how unliftio could be handled, yet.

Also, would it be able to take into account the different behavior of exception handling primitives (regarding using uninterruptibleMask in cleanup for example)?

I'm not sure what you mean.

[robinp]

Thanks for clarifying safe-exception usage. I had in mind the different constraint on say onException (MonadCatch vs MonadMask), but if dejafu is coded against those as well then fine.

For unliftio, could one bridge the constraints from concurrency with that from unliftio?

[barrucadu]

For unliftio, could one bridge the constraints from concurrency with that from unliftio?

You could certainly make a type which is an instance of both concurrency and unliftio (well, I don't see any immediate reasons why not), but I'm pretty sure the Program type which dejafu uses for testing can't be given a lawful MonadUnliftIO instance, because there's continuations and state involved. So in practice you wouldn't be able to test with dejafu something of type (MonadConc m, MonadUnliftIO m) => m a.