Access to more data from migration function.

[skilesare]

It would be great to have access to the following things from the migration function as they are sometimes necessary to properly migrate:

this - to get canister ID
args - args that the canister was called with during the upgrade
caller - the caller of the upgrade
- access to system items to schedule timers / send cycles

[alexandru-uta]

hey @skilesare , thanks for your message; could you also please share your use-case?

[skilesare]

Sure...

this - I need to pass my canister ID to a new component I'm instantiating that is part of my canister state.
args - I am a child canister in a fleet of canisters and I'm being upgraded. As part of the upgrade I need to be assigned to a parent canister that my owner is managing...It needs to pass the argument in the upgrade call.
caller - I only want to allow certain canisters to upgrade me(maybe certain controllers can stop/start but only specific canisters can upgrade...or I want to blackhole an upgrade)
system access - I need to set a timer to do some clean up.

The immediate use case is that I'd like to use my migration pattern(initially explained at https://forum.dfinity.org/t/day-origyn-motoko-gift-1-migration-pathway/14756 and actually implemented at https://github.com/icdevsorg/icrc75.mo/tree/main/src/migrations) in the migration function, but I'd need access to those things for it to work.

Original Request: https://forum.dfinity.org/t/new-motoko-migration-pattern/44057/6?u=skilesare