How to easily port the code for V3 pallets (early V3 syntax) to new syntax (4.0.0-dev)?

Question

We have a lot of pallets that have early V3 syntax, example here: https://github.com/threefoldtech/tfchain/blob/development/substrate-node/pallets/pallet-burning/src/lib.rs

We want to port them to the new pallet syntax of polkadot version 0.9.18, since we are also upgrading the entire runtime and node to be compatible with future upgrades / changes.

Also, what happens with the storage that is currently on our networks when we will upgrade all the pallets to use the new syntax? Will we need storage migration for all the objects?

Answer 1

You can take a look at the upgrade guidelines for converting to the new FRAME V2 macros.

There is also a checklist of things to check to make sure you don't inadvertently cause a breaking change.

In general, storage items should not need to be migrated at all, since the only main change here is syntax, not actually the underlying logic.

You can find a huge number of practical examples of migrations here: https://github.com/paritytech/substrate/issues/7882