[Staking] Noop refactor to prep pallet for currency fungible migration (

#5399)

This is a no-op refactor of staking pallet to move all `T::Currency` api
calls under one module.

A followup PR (#5501)
will implement the Currency <> Fungible migration for the pallet.

Introduces the new `asset` module that centralizes all interaction with
`T::Currency`. This is an attempt to try minimising staking logic
changes to minimal parts of the codebase.

## Things of note
- `T::Currency::free_balance` in current implementation includes both
staked (locked) and liquid tokens (kinda sounds wrong to call it free
then). This PR renames it to `stakeable_balance` (any better name
suggestions?). With #5501, this will become `free balance that can be
held/staked` + `already held/staked balance`.

substrate/frame/delegated-staking/src/impls.rs

@@ -124,7 +124,7 @@ impl<T: Config> DelegationMigrator for Pallet<T> {
 
 	/// Only used for testing.
 	#[cfg(feature = "runtime-benchmarks")]
-	fn migrate_to_direct_staker(agent: Agent<Self::AccountId>) {
+	fn force_kill_agent(agent: Agent<Self::AccountId>) {
 		<Agents<T>>::remove(agent.clone().get());
 		<Delegators<T>>::iter()
 			.filter(|(_, delegation)| delegation.agent == agent.clone().get())
@@ -136,8 +136,6 @@ impl<T: Config> DelegationMigrator for Pallet<T> {
 				);
 				<Delegators<T>>::remove(&delegator);
 			});
-
-		T::CoreStaking::migrate_to_direct_staker(&agent.get());
 	}
 }
 

substrate/frame/delegated-staking/src/tests.rs

@@ -676,7 +676,7 @@ mod staking_integration {
 			// in equal parts. lets try to migrate this nominator into delegate based stake.
 
 			// all balance currently is in 200
-			assert_eq!(Balances::free_balance(agent), agent_amount);
+			assert_eq!(pallet_staking::asset::stakeable_balance::<T>(&agent), agent_amount);
 
 			// to migrate, nominator needs to set an account as a proxy delegator where staked funds
 			// will be moved and delegated back to this old nominator account. This should be funded

substrate/frame/election-provider-multi-phase/test-staking-e2e/src/lib.rs

@@ -322,24 +322,24 @@ fn automatic_unbonding_pools() {
 		assert_eq!(<Runtime as pallet_nomination_pools::Config>::MaxUnbonding::get(), 1);
 
 		// init state of pool members.
-		let init_free_balance_2 = Balances::free_balance(2);
-		let init_free_balance_3 = Balances::free_balance(3);
+		let init_stakeable_balance_2 = pallet_staking::asset::stakeable_balance::<Runtime>(&2);
+		let init_stakeable_balance_3 = pallet_staking::asset::stakeable_balance::<Runtime>(&3);
 
 		let pool_bonded_account = Pools::generate_bonded_account(1);
 
 		// creates a pool with 5 bonded, owned by 1.
 		assert_ok!(Pools::create(RuntimeOrigin::signed(1), 5, 1, 1, 1));
-		assert_eq!(locked_amount_for(pool_bonded_account), 5);
+		assert_eq!(staked_amount_for(pool_bonded_account), 5);
 
 		let init_tvl = TotalValueLocked::<Runtime>::get();
 
 		// 2 joins the pool.
 		assert_ok!(Pools::join(RuntimeOrigin::signed(2), 10, 1));
-		assert_eq!(locked_amount_for(pool_bonded_account), 15);
+		assert_eq!(staked_amount_for(pool_bonded_account), 15);
 
 		// 3 joins the pool.
 		assert_ok!(Pools::join(RuntimeOrigin::signed(3), 10, 1));
-		assert_eq!(locked_amount_for(pool_bonded_account), 25);
+		assert_eq!(staked_amount_for(pool_bonded_account), 25);
 
 		assert_eq!(TotalValueLocked::<Runtime>::get(), 25);
 
@@ -350,7 +350,7 @@ fn automatic_unbonding_pools() {
 		assert_ok!(Pools::unbond(RuntimeOrigin::signed(2), 2, 10));
 
 		// amount is still locked in the pool, needs to wait for unbonding period.
-		assert_eq!(locked_amount_for(pool_bonded_account), 25);
+		assert_eq!(staked_amount_for(pool_bonded_account), 25);
 
 		// max chunks in the ledger are now filled up (`MaxUnlockingChunks == 1`).
 		assert_eq!(unlocking_chunks_of(pool_bonded_account), 1);
@@ -372,8 +372,8 @@ fn automatic_unbonding_pools() {
 		assert_eq!(current_era(), 3);
 		System::reset_events();
 
-		let locked_before_withdraw_pool = locked_amount_for(pool_bonded_account);
-		assert_eq!(Balances::free_balance(pool_bonded_account), 26);
+		let staked_before_withdraw_pool = staked_amount_for(pool_bonded_account);
+		assert_eq!(pallet_staking::asset::stakeable_balance::<Runtime>(&pool_bonded_account), 26);
 
 		// now unbonding 3 will work, although the pool's ledger still has the unlocking chunks
 		// filled up.
@@ -391,20 +391,21 @@ fn automatic_unbonding_pools() {
 		);
 
 		// balance of the pool remains the same, it hasn't withdraw explicitly from the pool yet.
-		assert_eq!(Balances::free_balance(pool_bonded_account), 26);
+		assert_eq!(pallet_staking::asset::stakeable_balance::<Runtime>(&pool_bonded_account), 26);
 		// but the locked amount in the pool's account decreases due to the auto-withdraw:
-		assert_eq!(locked_before_withdraw_pool - 10, locked_amount_for(pool_bonded_account));
+		assert_eq!(staked_before_withdraw_pool - 10, staked_amount_for(pool_bonded_account));
 
 		// TVL correctly updated.
 		assert_eq!(TotalValueLocked::<Runtime>::get(), 25 - 10);
 
 		// however, note that the withdrawing from the pool still works for 2, the funds are taken
-		// from the pool's free balance.
-		assert_eq!(Balances::free_balance(pool_bonded_account), 26);
+		// from the pool's non staked balance.
+		assert_eq!(pallet_staking::asset::stakeable_balance::<Runtime>(&pool_bonded_account), 26);
+		assert_eq!(pallet_staking::asset::staked::<Runtime>(&pool_bonded_account), 15);
 		assert_ok!(Pools::withdraw_unbonded(RuntimeOrigin::signed(2), 2, 10));
-		assert_eq!(Balances::free_balance(pool_bonded_account), 16);
+		assert_eq!(pallet_staking::asset::stakeable_balance::<Runtime>(&pool_bonded_account), 16);
 
-		assert_eq!(Balances::free_balance(2), 20);
+		assert_eq!(pallet_staking::asset::stakeable_balance::<Runtime>(&2), 20);
 		assert_eq!(TotalValueLocked::<Runtime>::get(), 15);
 
 		// 3 cannot withdraw yet.
@@ -423,9 +424,15 @@ fn automatic_unbonding_pools() {
 		assert_ok!(Pools::withdraw_unbonded(RuntimeOrigin::signed(3), 3, 10));
 
 		// final conditions are the expected.
-		assert_eq!(Balances::free_balance(pool_bonded_account), 6); // 5 init bonded + ED
-		assert_eq!(Balances::free_balance(2), init_free_balance_2);
-		assert_eq!(Balances::free_balance(3), init_free_balance_3);
+		assert_eq!(pallet_staking::asset::stakeable_balance::<Runtime>(&pool_bonded_account), 6); // 5 init bonded + ED
+		assert_eq!(
+			pallet_staking::asset::stakeable_balance::<Runtime>(&2),
+			init_stakeable_balance_2
+		);
+		assert_eq!(
+			pallet_staking::asset::stakeable_balance::<Runtime>(&3),
+			init_stakeable_balance_3
+		);
 
 		assert_eq!(TotalValueLocked::<Runtime>::get(), init_tvl);
 	});

substrate/frame/election-provider-multi-phase/test-staking-e2e/src/mock.rs

@@ -915,9 +915,8 @@ pub(crate) fn set_minimum_election_score(
 	.map_err(|_| ())
 }
 
-pub(crate) fn locked_amount_for(account_id: AccountId) -> Balance {
-	let lock = pallet_balances::Locks::<Runtime>::get(account_id);
-	lock[0].amount
+pub(crate) fn staked_amount_for(account_id: AccountId) -> Balance {
+	pallet_staking::asset::staked::<Runtime>(&account_id)
 }
 
 pub(crate) fn staking_events() -> Vec<pallet_staking::Event<Runtime>> {

substrate/frame/fast-unstake/src/tests.rs

@@ -137,15 +137,16 @@ fn deregister_works() {
 	ExtBuilder::default().build_and_execute(|| {
 		ErasToCheckPerBlock::<T>::put(1);
 
-		assert_eq!(<T as Config>::Currency::reserved_balance(&1), 0);
+		// reserved balance prior to registering for fast unstake.
+		let pre_reserved = <T as Config>::Currency::reserved_balance(&1);
 
 		// Controller account registers for fast unstake.
 		assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(1)));
-		assert_eq!(<T as Config>::Currency::reserved_balance(&1), Deposit::get());
+		assert_eq!(<T as Config>::Currency::reserved_balance(&1) - pre_reserved, Deposit::get());
 
 		// Controller then changes mind and deregisters.
 		assert_ok!(FastUnstake::deregister(RuntimeOrigin::signed(1)));
-		assert_eq!(<T as Config>::Currency::reserved_balance(&1), 0);
+		assert_eq!(<T as Config>::Currency::reserved_balance(&1) - pre_reserved, 0);
 
 		// Ensure stash no longer exists in the queue.
 		assert_eq!(Queue::<T>::get(1), None);
@@ -243,15 +244,19 @@ mod on_idle {
 			CurrentEra::<T>::put(BondingDuration::get());
 
 			// given
-			assert_eq!(<T as Config>::Currency::reserved_balance(&1), 0);
+			// reserved balance prior to registering for fast unstake.
+			let pre_reserved = <T as Config>::Currency::reserved_balance(&1);
 
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(1)));
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(3)));
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(5)));
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(7)));
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(9)));
 
-			assert_eq!(<T as Config>::Currency::reserved_balance(&1), Deposit::get());
+			assert_eq!(
+				<T as Config>::Currency::reserved_balance(&1) - pre_reserved,
+				Deposit::get()
+			);
 
 			assert_eq!(Queue::<T>::count(), 5);
 			assert_eq!(Head::<T>::get(), None);
@@ -279,6 +284,9 @@ mod on_idle {
 			// when
 			next_block(true);
 
+			// pre_reserve may change due to unstaked amount.
+			let pre_reserved = <T as Config>::Currency::reserved_balance(&1);
+
 			// then
 			assert_eq!(
 				Head::<T>::get(),
@@ -289,7 +297,7 @@ mod on_idle {
 			);
 			assert_eq!(Queue::<T>::count(), 3);
 
-			assert_eq!(<T as Config>::Currency::reserved_balance(&1), 0);
+			assert_eq!(<T as Config>::Currency::reserved_balance(&1) - pre_reserved, 0);
 
 			assert_eq!(
 				fast_unstake_events_since_last_call(),

substrate/frame/nomination-pools/benchmarking/src/inner.rs

@@ -41,7 +41,7 @@ use sp_runtime::{
 	traits::{Bounded, StaticLookup, Zero},
 	Perbill,
 };
-use sp_staking::EraIndex;
+use sp_staking::{EraIndex, StakingUnchecked};
 // `frame_benchmarking::benchmarks!` macro needs this
 use pallet_nomination_pools::Call;
 
@@ -131,6 +131,8 @@ fn migrate_to_transfer_stake<T: Config>(pool_id: PoolId) {
 			)
 			.expect("member should have enough balance to transfer");
 		});
+
+	pallet_staking::Pallet::<T>::migrate_to_direct_staker(&pool_acc);
 }
 
 fn vote_to_balance<T: pallet_nomination_pools::Config>(

substrate/frame/nomination-pools/src/adapter.rs

@@ -460,6 +460,6 @@ impl<
 
 	#[cfg(feature = "runtime-benchmarks")]
 	fn remove_as_agent(pool: Pool<Self::AccountId>) {
-		Delegation::migrate_to_direct_staker(pool.into())
+		Delegation::force_kill_agent(pool.into())
 	}
 }

substrate/frame/offences/benchmarking/src/inner.rs

@@ -20,7 +20,7 @@
 use alloc::{vec, vec::Vec};
 
 use frame_benchmarking::v1::{account, benchmarks};
-use frame_support::traits::{Currency, Get};
+use frame_support::traits::Get;
 use frame_system::{Config as SystemConfig, Pallet as System, RawOrigin};
 
 use sp_runtime::{
@@ -77,8 +77,7 @@ where
 }
 
 type LookupSourceOf<T> = <<T as SystemConfig>::Lookup as StaticLookup>::Source;
-type BalanceOf<T> =
-	<<T as StakingConfig>::Currency as Currency<<T as SystemConfig>::AccountId>>::Balance;
+type BalanceOf<T> = <T as StakingConfig>::CurrencyBalance;
 
 struct Offender<T: Config> {
 	pub controller: T::AccountId,
@@ -89,7 +88,7 @@ struct Offender<T: Config> {
 }
 
 fn bond_amount<T: Config>() -> BalanceOf<T> {
-	T::Currency::minimum_balance().saturating_mul(10_000u32.into())
+	pallet_staking::asset::existential_deposit::<T>().saturating_mul(10_000u32.into())
 }
 
 fn create_offender<T: Config>(n: u32, nominators: u32) -> Result<Offender<T>, &'static str> {
@@ -99,7 +98,7 @@ fn create_offender<T: Config>(n: u32, nominators: u32) -> Result<Offender<T>, &'
 	let amount = bond_amount::<T>();
 	// add twice as much balance to prevent the account from being killed.
 	let free_amount = amount.saturating_mul(2u32.into());
-	T::Currency::make_free_balance_be(&stash, free_amount);
+	pallet_staking::asset::set_stakeable_balance::<T>(&stash, free_amount);
 	Staking::<T>::bond(
 		RawOrigin::Signed(stash.clone()).into(),
 		amount,
@@ -116,7 +115,7 @@ fn create_offender<T: Config>(n: u32, nominators: u32) -> Result<Offender<T>, &'
 	for i in 0..nominators {
 		let nominator_stash: T::AccountId =
 			account("nominator stash", n * MAX_NOMINATORS + i, SEED);
-		T::Currency::make_free_balance_be(&nominator_stash, free_amount);
+		pallet_staking::asset::set_stakeable_balance::<T>(&nominator_stash, free_amount);
 
 		Staking::<T>::bond(
 			RawOrigin::Signed(nominator_stash.clone()).into(),
@@ -172,6 +171,14 @@ fn make_offenders<T: Config>(
 }
 
 benchmarks! {
+	where_clause {
+		where
+		<T as frame_system::Config>::RuntimeEvent: TryInto<pallet_staking::Event<T>>,
+		<T as frame_system::Config>::RuntimeEvent: TryInto<pallet_balances::Event<T>>,
+		<T as frame_system::Config>::RuntimeEvent: TryInto<pallet_offences::Event>,
+		<T as frame_system::Config>::RuntimeEvent: TryInto<frame_system::Event<T>>,
+	}
+
 	report_offence_grandpa {
 		let n in 0 .. MAX_NOMINATORS.min(MaxNominationsOf::<T>::get());
 
@@ -196,17 +203,19 @@ benchmarks! {
 		let _ = Offences::<T>::report_offence(reporters, offence);
 	}
 	verify {
-		// make sure that all slashes have been applied
 		#[cfg(test)]
-		assert_eq!(
-			System::<T>::event_count(), 0
-			+ 1 // offence
-			+ 3 // reporter (reward + endowment)
-			+ 1 // offenders reported
-			+ 3 // offenders slashed
-			+ 1 // offenders chilled
-			+ 3 * n // nominators slashed
-		);
+		{
+			// make sure that all slashes have been applied
+			// (n nominators + one validator) * (slashed + unlocked) + deposit to reporter + reporter
+			// account endowed + some funds rescinded from issuance.
+			assert_eq!(System::<T>::read_events_for_pallet::<pallet_balances::Event<T>>().len(), 2 * (n + 1) as usize + 3);
+			// (n nominators + one validator) * slashed + Slash Reported
+			assert_eq!(System::<T>::read_events_for_pallet::<pallet_staking::Event<T>>().len(), 1 * (n + 1) as usize + 1);
+			// offence
+			assert_eq!(System::<T>::read_events_for_pallet::<pallet_offences::Event>().len(), 1);
+			// reporter new account
+			assert_eq!(System::<T>::read_events_for_pallet::<frame_system::Event<T>>().len(), 1);
+		}
 	}
 
 	report_offence_babe {
@@ -233,17 +242,19 @@ benchmarks! {
 		let _ = Offences::<T>::report_offence(reporters, offence);
 	}
 	verify {
-		// make sure that all slashes have been applied
 		#[cfg(test)]
-		assert_eq!(
-			System::<T>::event_count(), 0
-			+ 1 // offence
-			+ 3 // reporter (reward + endowment)
-			+ 1 // offenders reported
-			+ 3 // offenders slashed
-			+ 1 // offenders chilled
-			+ 3 * n // nominators slashed
-		);
+		{
+			// make sure that all slashes have been applied
+			// (n nominators + one validator) * (slashed + unlocked) + deposit to reporter + reporter
+			// account endowed + some funds rescinded from issuance.
+			assert_eq!(System::<T>::read_events_for_pallet::<pallet_balances::Event<T>>().len(), 2 * (n + 1) as usize + 3);
+			// (n nominators + one validator) * slashed + Slash Reported
+			assert_eq!(System::<T>::read_events_for_pallet::<pallet_staking::Event<T>>().len(), 1 * (n + 1) as usize + 1);
+			// offence
+			assert_eq!(System::<T>::read_events_for_pallet::<pallet_offences::Event>().len(), 1);
+			// reporter new account
+			assert_eq!(System::<T>::read_events_for_pallet::<frame_system::Event<T>>().len(), 1);
+		}
 	}
 
 	impl_benchmark_test_suite!(Pallet, crate::mock::new_test_ext(), crate::mock::Test);