Allow privileged virtual bond in Staking pallet (#3889)

This is the first PR in preparation for https://github.com/paritytech/polkadot-sdk/issues/454. ## Follow ups: - https://github.com/paritytech/polkadot-sdk/pull/3904. - https://github.com/paritytech/polkadot-sdk/pull/3905. Overall changes are documented here (lot more visual 😍): https://hackmd.io/@ak0n/454-np-governance [Maybe followup](https://github.com/paritytech/polkadot-sdk/issues/4217) with migration of storage item `VirtualStakers` as a bool or enum in `Ledger`. ## Context We want to achieve a way for a user (`Delegator`) to delegate their funds to another account (`Agent`). Delegate implies the funds are locked in delegator account itself. Agent can act on behalf of delegator to stake directly on Staking pallet. The delegation feature is added to Staking via another pallet `delegated-staking` worked on [here](https://github.com/paritytech/polkadot-sdk/pull/3904). ## Introduces: ### StakingUnchecked Trait As the name implies, this trait allows unchecked (non-locked) mutation of staking ledger. These apis are only meant to be used by other pallets in the runtime and should not be exposed directly to user code path. Also related: https://github.com/paritytech/polkadot-sdk/issues/3888. ### Virtual Bond Allows other pallets to stake via staking pallet while managing the locks on these accounts themselves. Introduces another storage `VirtualStakers` that whitelist these accounts. We also restrict virtual stakers to set reward account as themselves. Since the account has no locks, we cannot support compounding of rewards. Conservatively, we require them to set a separate account different from the staker. Since these are code managed, it should be easy for another pallet to redistribute reward and rebond them. ### Slashes Since there is no actual lock maintained by staking-pallet for virtual stakers, this pallet does not apply any slashes. It is then important for pallets managing virtual stakers to listen to slashing events and apply necessary slashes.
2026-07-22 12:35:42 +00:00 · 2024-04-20 02:05:34 +02:00
parent 4eabe5e0dd
commit e504c41a5a
9 changed files with 514 additions and 73 deletions
@@ -27,7 +27,7 @@ use frame_support::{
 	assert_noop, assert_ok, assert_storage_noop,
 	dispatch::{extract_actual_weight, GetDispatchInfo, WithPostDispatchInfo},
 	pallet_prelude::*,
-	traits::{Currency, Get, ReservableCurrency},
+	traits::{Currency, Get, InspectLockableCurrency, ReservableCurrency},
 };

 use mock::*;
@@ -623,12 +623,8 @@ fn nominating_and_rewards_should_work() {
 			));
 			assert_ok!(Staking::nominate(RuntimeOrigin::signed(1), vec![11, 21, 31]));

-			assert_ok!(Staking::bond(
-				RuntimeOrigin::signed(3),
-				1000,
-				RewardDestination::Account(3)
-			));
-			assert_ok!(Staking::nominate(RuntimeOrigin::signed(3), vec![11, 21, 41]));
+			// the second nominator is virtual.
+			bond_virtual_nominator(3, 333, 1000, vec![11, 21, 41]);

 			// the total reward for era 0
 			let total_payout_0 = current_total_payout_for_duration(reward_time_per_era());
@@ -694,10 +690,12 @@ fn nominating_and_rewards_should_work() {
 			);
 			// Nominator 3: has [400/1800 ~ 2/9 from 10] + [600/2200 ~ 3/11 from 21]'s reward. ==>
 			// 2/9 + 3/11
+			assert_eq!(Balances::total_balance(&3), initial_balance);
+			// 333 is the reward destination for 3.
 			assert_eq_error_rate!(
-				Balances::total_balance(&3),
-				initial_balance + (2 * payout_for_11 / 9 + 3 * payout_for_21 / 11),
-				2,
+				Balances::total_balance(&333),
+				2 * payout_for_11 / 9 + 3 * payout_for_21 / 11,
+				2
 			);

 			// Validator 11: got 800 / 1800 external stake => 8/18 =? 4/9 => Validator's share = 5/9
@@ -1893,7 +1891,7 @@ fn reap_stash_works() {
 		.balance_factor(10)
 		.build_and_execute(|| {
 			// given
-			assert_eq!(Balances::free_balance(11), 10 * 1000);
+			assert_eq!(Balances::balance_locked(STAKING_ID, &11), 10 * 1000);
 			assert_eq!(Staking::bonded(&11), Some(11));

 			assert!(<Ledger<Test>>::contains_key(&11));
@@ -1919,6 +1917,8 @@ fn reap_stash_works() {
 			assert!(!<Bonded<Test>>::contains_key(&11));
 			assert!(!<Validators<Test>>::contains_key(&11));
 			assert!(!<Payee<Test>>::contains_key(&11));
+			// lock is removed.
+			assert_eq!(Balances::balance_locked(STAKING_ID, &11), 0);
 		});
 }

@@ -6849,6 +6849,226 @@ mod staking_interface {
 	}
 }

+mod staking_unchecked {
+	use sp_staking::{Stake, StakingInterface, StakingUnchecked};
+
+	use super::*;
+
+	#[test]
+	fn virtual_bond_does_not_lock() {
+		ExtBuilder::default().build_and_execute(|| {
+			mock::start_active_era(1);
+			assert_eq!(Balances::free_balance(10), 1);
+			// 10 can bond more than its balance amount since we do not require lock for virtual
+			// bonding.
+			assert_ok!(<Staking as StakingUnchecked>::virtual_bond(&10, 100, &15));
+			// nothing is locked on 10.
+			assert_eq!(Balances::balance_locked(STAKING_ID, &10), 0);
+			// adding more balance does not lock anything as well.
+			assert_ok!(<Staking as StakingInterface>::bond_extra(&10, 1000));
+			// but ledger is updated correctly.
+			assert_eq!(
+				<Staking as StakingInterface>::stake(&10),
+				Ok(Stake { total: 1100, active: 1100 })
+			);
+
+			// lets try unbonding some amount.
+			assert_ok!(<Staking as StakingInterface>::unbond(&10, 200));
+			assert_eq!(
+				Staking::ledger(10.into()).unwrap(),
+				StakingLedgerInspect {
+					stash: 10,
+					total: 1100,
+					active: 1100 - 200,
+					unlocking: bounded_vec![UnlockChunk { value: 200, era: 1 + 3 }],
+					legacy_claimed_rewards: bounded_vec![],
+				}
+			);
+
+			assert_eq!(
+				<Staking as StakingInterface>::stake(&10),
+				Ok(Stake { total: 1100, active: 900 })
+			);
+			// still no locks.
+			assert_eq!(Balances::balance_locked(STAKING_ID, &10), 0);
+
+			mock::start_active_era(2);
+			// cannot withdraw without waiting for unbonding period.
+			assert_ok!(<Staking as StakingInterface>::withdraw_unbonded(10, 0));
+			assert_eq!(
+				<Staking as StakingInterface>::stake(&10),
+				Ok(Stake { total: 1100, active: 900 })
+			);
+
+			// in era 4, 10 can withdraw unlocking amount.
+			mock::start_active_era(4);
+			assert_ok!(<Staking as StakingInterface>::withdraw_unbonded(10, 0));
+			assert_eq!(
+				<Staking as StakingInterface>::stake(&10),
+				Ok(Stake { total: 900, active: 900 })
+			);
+
+			// unbond all.
+			assert_ok!(<Staking as StakingInterface>::unbond(&10, 900));
+			assert_eq!(
+				<Staking as StakingInterface>::stake(&10),
+				Ok(Stake { total: 900, active: 0 })
+			);
+			mock::start_active_era(7);
+			assert_ok!(<Staking as StakingInterface>::withdraw_unbonded(10, 0));
+
+			// ensure withdrawing all amount cleans up storage.
+			assert_eq!(Staking::ledger(10.into()), Err(Error::<Test>::NotStash));
+			assert_eq!(VirtualStakers::<Test>::contains_key(10), false);
+		})
+	}
+
+	#[test]
+	fn virtual_staker_cannot_pay_reward_to_self_account() {
+		ExtBuilder::default().build_and_execute(|| {
+			// cannot set payee to self
+			assert_noop!(
+				<Staking as StakingUnchecked>::virtual_bond(&10, 100, &10),
+				Error::<Test>::RewardDestinationRestricted
+			);
+
+			// to another account works
+			assert_ok!(<Staking as StakingUnchecked>::virtual_bond(&10, 100, &11));
+
+			// cannot set via set_payee as well.
+			assert_noop!(
+				<Staking as StakingInterface>::update_payee(&10, &10),
+				Error::<Test>::RewardDestinationRestricted
+			);
+		});
+	}
+
+	#[test]
+	fn virtual_staker_cannot_bond_again() {
+		ExtBuilder::default().build_and_execute(|| {
+			// 200 virtual bonds
+			bond_virtual_nominator(200, 201, 500, vec![11, 21]);
+
+			// Tries bonding again
+			assert_noop!(
+				<Staking as StakingUnchecked>::virtual_bond(&200, 200, &201),
+				Error::<Test>::AlreadyBonded
+			);
+
+			// And again with a different reward destination.
+			assert_noop!(
+				<Staking as StakingUnchecked>::virtual_bond(&200, 200, &202),
+				Error::<Test>::AlreadyBonded
+			);
+
+			// Direct bond is not allowed as well.
+			assert_noop!(
+				<Staking as StakingInterface>::bond(&200, 200, &202),
+				Error::<Test>::AlreadyBonded
+			);
+		});
+	}
+
+	#[test]
+	fn normal_staker_cannot_virtual_bond() {
+		ExtBuilder::default().build_and_execute(|| {
+			// 101 is a nominator trying to virtual bond
+			assert_noop!(
+				<Staking as StakingUnchecked>::virtual_bond(&101, 200, &102),
+				Error::<Test>::AlreadyBonded
+			);
+
+			// validator 21 tries to virtual bond
+			assert_noop!(
+				<Staking as StakingUnchecked>::virtual_bond(&21, 200, &22),
+				Error::<Test>::AlreadyBonded
+			);
+		});
+	}
+
+	#[test]
+	fn migrate_virtual_staker() {
+		ExtBuilder::default().build_and_execute(|| {
+			// give some balance to 200
+			Balances::make_free_balance_be(&200, 2000);
+
+			// stake
+			assert_ok!(Staking::bond(RuntimeOrigin::signed(200), 1000, RewardDestination::Staked));
+			assert_eq!(Balances::balance_locked(crate::STAKING_ID, &200), 1000);
+
+			// migrate them to virtual staker
+			<Staking as StakingUnchecked>::migrate_to_virtual_staker(&200);
+			// payee needs to be updated to a non-stash account.
+			assert_ok!(<Staking as StakingInterface>::update_payee(&200, &201));
+
+			// ensure the balance is not locked anymore
+			assert_eq!(Balances::balance_locked(crate::STAKING_ID, &200), 0);
+
+			// and they are marked as virtual stakers
+			assert_eq!(Pallet::<Test>::is_virtual_staker(&200), true);
+		});
+	}
+
+	#[test]
+	fn virtual_nominators_are_lazily_slashed() {
+		ExtBuilder::default().build_and_execute(|| {
+			mock::start_active_era(1);
+			let slash_percent = Perbill::from_percent(5);
+			let initial_exposure = Staking::eras_stakers(active_era(), &11);
+			// 101 is a nominator for 11
+			assert_eq!(initial_exposure.others.first().unwrap().who, 101);
+			// make 101 a virtual nominator
+			<Staking as StakingUnchecked>::migrate_to_virtual_staker(&101);
+			// set payee different to self.
+			assert_ok!(<Staking as StakingInterface>::update_payee(&101, &102));
+
+			// cache values
+			let nominator_stake = Staking::ledger(101.into()).unwrap().active;
+			let nominator_balance = balances(&101).0;
+			let validator_stake = Staking::ledger(11.into()).unwrap().active;
+			let validator_balance = balances(&11).0;
+			let exposed_stake = initial_exposure.total;
+			let exposed_validator = initial_exposure.own;
+			let exposed_nominator = initial_exposure.others.first().unwrap().value;
+
+			// 11 goes offline
+			on_offence_now(
+				&[OffenceDetails { offender: (11, initial_exposure.clone()), reporters: vec![] }],
+				&[slash_percent],
+			);
+
+			let slash_amount = slash_percent * exposed_stake;
+			let validator_share =
+				Perbill::from_rational(exposed_validator, exposed_stake) * slash_amount;
+			let nominator_share =
+				Perbill::from_rational(exposed_nominator, exposed_stake) * slash_amount;
+
+			// both slash amounts need to be positive for the test to make sense.
+			assert!(validator_share > 0);
+			assert!(nominator_share > 0);
+
+			// both stakes must have been decreased pro-rata.
+			assert_eq!(
+				Staking::ledger(101.into()).unwrap().active,
+				nominator_stake - nominator_share
+			);
+			assert_eq!(
+				Staking::ledger(11.into()).unwrap().active,
+				validator_stake - validator_share
+			);
+
+			// validator balance is slashed as usual
+			assert_eq!(balances(&11).0, validator_balance - validator_share);
+			// Because slashing happened.
+			assert!(is_disabled(11));
+
+			// but virtual nominator's balance is not slashed.
+			assert_eq!(Balances::free_balance(&101), nominator_balance);
+			// but slash is broadcasted to slash observers.
+			assert_eq!(SlashObserver::get().get(&101).unwrap(), &nominator_share);
+		})
+	}
+}
 mod ledger {
 	use super::*;

@@ -7327,7 +7547,6 @@ mod ledger {

 mod ledger_recovery {
 	use super::*;
-	use frame_support::traits::InspectLockableCurrency;

 	#[test]
 	fn inspect_recovery_ledger_simple_works() {