Function is_recovering_from_trap

pub fn is_recovering_from_trap() -> bool

Tells you whether the current async fn is being canceled due to a trap/panic.

If a function traps/panics, then the canister state is rewound to the beginning of the function. However, due to the way async works, the beginning of the function as the IC understands it is actually the most recent await from an inter-canister-call. This means that part of the function will have executed, and part of it won’t.

When this happens the CDK will cancel the task, causing destructors to be run. If you need any functions to be run no matter what happens, they should happen in a destructor; the scopeguard crate provides a convenient wrapper for this. In a destructor, is_recovering_from_trap serves the same purpose as std::thread::panicking - it tells you whether the destructor is executing because of a trap, as opposed to just because the scope was exited, so you could e.g. implement mutex poisoning.