nomination-pools: add permissionless condition to chill

prdoc/pr_3453.prdoc

@@ -0,0 +1,12 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: "[pallet-nomination-pools]: `chill` is permissionless if depositor's stake is less than `min_nominator_bond`"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Nomination pools currently have an issue whereby member funds cannot be unbonded if the depositor bonded amount is less than MinNominatorBond.
+      This PR makes the `chill` function permissionless if this condition is met.
+crates:
+  - name: pallet-nomination-pools

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

@@ -2411,6 +2411,16 @@ pub mod pallet {
 			let who = ensure_signed(origin)?;
 			let bonded_pool = BondedPool::<T>::get(pool_id).ok_or(Error::<T>::PoolNotFound)?;
 			ensure!(bonded_pool.can_nominate(&who), Error::<T>::NotNominator);
+
+			let depositor_points = PoolMembers::<T>::get(&bonded_pool.roles.depositor)
+				.ok_or(Error::<T>::PoolMemberNotFound)?
+				.active_points();
+
+			ensure!(
+				bonded_pool.points_to_balance(depositor_points) >= Self::depositor_min_bond(),
+				Error::<T>::MinimumBondNotMet
+			);
+
 			T::Staking::nominate(&bonded_pool.bonded_account(), validators)
 		}
 
@@ -2573,18 +2583,42 @@ pub mod pallet {
 
 		/// Chill on behalf of the pool.
 		///
-		/// The dispatch origin of this call must be signed by the pool nominator or the pool
+		/// The dispatch origin of this call can be signed by the pool nominator or the pool
 		/// root role, same as [`Pallet::nominate`].
 		///
+		/// Under certain conditions, this call can be dispatched permissionlessly (i.e. by any
+		/// account).
+		///
+		/// # Conditions for a permissionless dispatch
+		///
+		/// * When pool depositor has less than `MinNominatorBond` staked, otherwise  pool members
+		///   are unable to unbond.
+		///
+		/// # Conditions for permissioned dispatch
+		///
+		/// * The caller has a nominator or root role of the pool.
+		///
 		/// This directly forward the call to the staking pallet, on behalf of the pool bonded
 		/// account.
 		#[pallet::call_index(13)]
 		#[pallet::weight(T::WeightInfo::chill())]
 		pub fn chill(origin: OriginFor<T>, pool_id: PoolId) -> DispatchResult {
 			let who = ensure_signed(origin)?;
+
 			let bonded_pool = BondedPool::<T>::get(pool_id).ok_or(Error::<T>::PoolNotFound)?;
-			ensure!(bonded_pool.can_nominate(&who), Error::<T>::NotNominator);
-			T::Staking::chill(&bonded_pool.bonded_account())
+
+			let depositor_points = PoolMembers::<T>::get(&bonded_pool.roles.depositor)
+				.ok_or(Error::<T>::PoolMemberNotFound)?
+				.active_points();
+
+			if bonded_pool.points_to_balance(depositor_points) <
+				T::Staking::minimum_nominator_bond()
+			{
+				T::Staking::chill(&bonded_pool.bonded_account())
+			} else {
+				ensure!(bonded_pool.can_nominate(&who), Error::<T>::NotNominator);
+				T::Staking::chill(&bonded_pool.bonded_account())
+			}
 		}
 
 		/// `origin` bonds funds from `extra` for some pool member `member` into their respective

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

@@ -4848,6 +4848,18 @@ mod nominate {
 				Error::<Runtime>::NotNominator
 			);
 
+			// if `depositor` stake is less than the `MinimumNominatorBond`, they can't nominate
+			StakingMinBond::set(20);
+
+			// Can't nominate if depositor's stake is less than the `MinimumNominatorBond`
+			assert_noop!(
+				Pools::nominate(RuntimeOrigin::signed(900), 1, vec![21]),
+				Error::<Runtime>::MinimumBondNotMet
+			);
+
+			// restore `MinimumNominatorBond`
+			StakingMinBond::set(10);
+
 			// Root can nominate
 			assert_ok!(Pools::nominate(RuntimeOrigin::signed(900), 1, vec![21]));
 			assert_eq!(Nominations::get().unwrap(), vec![21]);
@@ -7338,3 +7350,33 @@ mod slash {
 		});
 	}
 }
+
+mod chill {
+	use super::*;
+
+	#[test]
+	fn chill_works() {
+		ExtBuilder::default().build_and_execute(|| {
+			// only nominator or root can chill
+			assert_noop!(
+				Pools::chill(RuntimeOrigin::signed(10), 1),
+				Error::<Runtime>::NotNominator
+			);
+
+			// root can chill and re-nominate
+			assert_ok!(Pools::chill(RuntimeOrigin::signed(900), 1));
+			assert_ok!(Pools::nominate(RuntimeOrigin::signed(900), 1, vec![31]));
+
+			// nominator can chill and re-nominate
+			assert_ok!(Pools::chill(RuntimeOrigin::signed(901), 1));
+			assert_ok!(Pools::nominate(RuntimeOrigin::signed(901), 1, vec![31]));
+
+			// if `depositor` stake is less than the `MinimumNominatorBond`, then this call
+			// becomes permissionless;
+			StakingMinBond::set(20);
+
+			// any account can chill
+			assert_ok!(Pools::chill(RuntimeOrigin::signed(10), 1));
+		})
+	}
+}