migrate virtual stakers code

substrate/frame/staking/src/pallet/impls.rs

@@ -1159,8 +1159,38 @@ impl<T: Config> Pallet<T> {
  }
 
  pub(super) fn do_migrate_currency(stash: &T::AccountId) -> DispatchResult {
- // we can't do anything for virtual stakers since their funds are not managed/held by
- // this pallet.
+ if Self::is_virtual_staker(stash) {
+ // Funds for virtual stakers not managed/held by this pallet. We only need to clear
+ // the extra consumer we used to have with OldCurrency.
+ frame_system::Pallet::<T>::dec_consumers(&stash);
+
+ // The delegation system that manages the virtual staker needed to increment provider
+ // previously because of the consumer needed by this pallet. In reality, this stash
+ // is just a key for managing the ledger and the account does not need to hold any
+ // balance or exist. We decrement this provider.
+ let actual_providers = frame_system::Pallet::<T>::providers(stash);
+
+ let expected_providers =
+ // provider is expected to be 1 but someone can always transfer some free funds to
+ // these accounts, increasing the provider.
+ if asset::free_to_stake::<T>(&stash) >= asset::existential_deposit::<T>() {
+ 2
+ } else {
+ 1
+ };
+
+ // We should never have more than expected providers.
+ ensure!(actual_providers <= expected_providers, Error::<T>::BadState);
+
+ // if actual provider is less than expected, it is already migrated.
+ ensure!(actual_providers == expected_providers, Error::<T>::AlreadyMigrated);
+
+ // dec provider
+ let _ = frame_system::Pallet::<T>::dec_providers(&stash)?;
+
+ return Ok(())
+ }
+
  ensure!(!Self::is_virtual_staker(stash), Error::<T>::VirtualStakerNotAllowed);
  let ledger = Self::ledger(Stash(stash.clone()))?;
  let locked: BalanceOf<T> = T::OldCurrency::balance_locked(STAKING_ID, stash).into();