pallet-staking: Add extrinsic force_apply_min_commission (#10786)

* pallet-staking: Add extrinsic `force_apply_min_commission`

* Add benchmarks

* cargo run --quiet --profile=production  --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Bound iteration by  max_validator_count

* cargo run --quiet --profile=production  --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Only apply to 1 validator

* Update doc comments

* Uncomment tests

* cargo run --quiet --profile=production  --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Accept signed origins

* cargo run --quiet --profile=production  --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Remove contains_key check

* Add test for try_mutate_exists

* Impove try_mutate_exists docs

* Delete redundant try_mutate_exists tests;

* Delete residual from removed test

* cargo run --quiet --profile=production  --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Return an error when the stash does not exist

* Update try_mutate_exist doc wording

* Update frame/staking/src/pallet/mod.rs

* Apply suggestions from code review

Co-authored-by: Parity Bot <[email protected]>
Co-authored-by: Shawn Tabrizi <[email protected]>

frame/staking/src/benchmarking.rs

@@ -900,6 +900,35 @@ benchmarks! {
 		assert!(!T::SortedListProvider::contains(&stash));
 	}
 
+	force_apply_min_commission {
+		// Clean up any existing state
+		clear_validators_and_nominators::<T>();
+
+		// Create a validator with a commission of 50%
+		let (stash, controller) =
+			create_stash_controller::<T>(1, 1, RewardDestination::Staked)?;
+		let validator_prefs =
+			ValidatorPrefs { commission: Perbill::from_percent(50), ..Default::default() };
+		Staking::<T>::validate(RawOrigin::Signed(controller).into(), validator_prefs)?;
+
+		// Sanity check
+		assert_eq!(
+			Validators::<T>::get(&stash),
+			ValidatorPrefs { commission: Perbill::from_percent(50), ..Default::default() }
+		);
+
+		// Set the min commission to 75%
+		MinCommission::<T>::set(Perbill::from_percent(75));
+		let caller = whitelisted_caller();
+	}: _(RawOrigin::Signed(caller), stash.clone())
+	verify {
+		// The validators commission has been bumped to 75%
+		assert_eq!(
+			Validators::<T>::get(&stash),
+			ValidatorPrefs { commission: Perbill::from_percent(75), ..Default::default() }
+		);
+	}
+
 	impl_benchmark_test_suite!(
 		Staking,
 		crate::mock::ExtBuilder::default().has_stakers(true),

frame/staking/src/pallet/mod.rs

@@ -1616,6 +1616,28 @@ pub mod pallet {
 			Self::chill_stash(&stash);
 			Ok(())
 		}
+
+		/// Force a validator to have at least the minimum commission. This will not affect a
+		/// validator who already has a commission greater than or equal to the minimum. Any account
+		/// can call this.
+		#[pallet::weight(T::WeightInfo::force_apply_min_commission())]
+		pub fn force_apply_min_commission(
+			origin: OriginFor<T>,
+			validator_stash: T::AccountId,
+		) -> DispatchResult {
+			ensure_signed(origin)?;
+			let min_commission = MinCommission::<T>::get();
+			Validators::<T>::try_mutate_exists(validator_stash, |maybe_prefs| {
+				maybe_prefs
+					.as_mut()
+					.map(|prefs| {
+						(prefs.commission < min_commission)
+							.then(|| prefs.commission = min_commission)
+					})
+					.ok_or(Error::<T>::NotStash)
+			})?;
+			Ok(())
+		}
 	}
 }
 

frame/staking/src/tests.rs

@@ -4711,3 +4711,38 @@ mod sorted_list_provider {
 		});
 	}
 }
+
+#[test]
+fn force_apply_min_commission_works() {
+	let prefs = |c| ValidatorPrefs { commission: Perbill::from_percent(c), blocked: false };
+	let validators = || Validators::<Test>::iter().collect::<Vec<_>>();
+	ExtBuilder::default().build_and_execute(|| {
+		assert_ok!(Staking::validate(Origin::signed(30), prefs(10)));
+		assert_ok!(Staking::validate(Origin::signed(20), prefs(5)));
+
+		// Given
+		assert_eq!(validators(), vec![(31, prefs(10)), (21, prefs(5)), (11, prefs(0))]);
+		MinCommission::<Test>::set(Perbill::from_percent(5));
+
+		// When applying to a commission greater than min
+		assert_ok!(Staking::force_apply_min_commission(Origin::signed(1), 31));
+		// Then the commission is not changed
+		assert_eq!(validators(), vec![(31, prefs(10)), (21, prefs(5)), (11, prefs(0))]);
+
+		// When applying to a commission that is equal to min
+		assert_ok!(Staking::force_apply_min_commission(Origin::signed(1), 21));
+		// Then the commission is not changed
+		assert_eq!(validators(), vec![(31, prefs(10)), (21, prefs(5)), (11, prefs(0))]);
+
+		// When applying to a commission that is less than the min
+		assert_ok!(Staking::force_apply_min_commission(Origin::signed(1), 11));
+		// Then the commission is bumped to the min
+		assert_eq!(validators(), vec![(31, prefs(10)), (21, prefs(5)), (11, prefs(5))]);
+
+		// When applying commission to a validator that doesn't exist then storage is not altered
+		assert_noop!(
+			Staking::force_apply_min_commission(Origin::signed(1), 420),
+			Error::<Test>::NotStash
+		);
+	});
+}