Implementing hooks for Flow streams

[PaulRBerg]

Received a feature request for this from a user. They were originally looking for permissioned withdrawals, but we ended up talking about hooks - they said hooks would have worked, too.

WDYT @sablier-labs/evm?

[andreivladbrg]

we have: #45

we can do this. but i'd say that it would be more complex compared to lockup

[PaulRBerg]

Why? We'd only do it for senders.

[smol-ninja]

There could be a security risk where sender can block withdraw from the stream by reverting on the hook callback. Senders can be a Gnosis SAFE in the beginning so we won't see it as a red flag and later on they can add module to their Gnosis SAFE that reverts on the hook callback.

Unless, we do it the old way i.e. put it inside a try..catch block but then recipient can avoid the hook call by passing insufficient gas.

It can be a problem either way.

[PaulRBerg]

oh, right .. this is why we implemented the hook allowlist 🫤

I will close this discussion. The better solution for the problem reported in the OP is to allow users to make withdrawals permissioned.

[smol-ninja]

The way our hooks work is that they require the target to be the recipient i.e. users will have to deposit their streams into the target contract. So, how would it work in case of this user? Are you sure hooks can solve his problem?

Or we can think of re-designing hooks from the scratch to make them usable in this way.

[PaulRBerg]

It's a case of the sender wanting to be notified that a withdrawal was performed.

[smol-ninja]

See the above comment.