stake-tracker feedback PR (#4411)

- Changes the target list score type from balance to `u128`
(`ExtendedBalance`)
  - simplifies `balance/ vote_weight/ extended_balance` conversions
  - relies less on the currency total issuance call
  - ensures approval stake calculations/storage is safe 
- Simplifies stake tracker logic
  - removes a few redundant checks
  - split `on_stake_update` code
- Ensures `VoterUpdateMode` is taken into consideration in try-state
checks
  - use voter mode lazy in benchmarks
  - update weights + check the diff with voter lazy 
- Docs improvements
- All tests passing after merging validator disabling and virtual
stakers

**new**
- ensures duplicate nominations are dedup before calculating the
approvals stake
- chills nominator after total slash to ensure the target can be
reaped/kill without leaving nominations behind.
- ensures that switching from validator to nominator and back is correct
- a nominator may have an entry in the targetlist (if it was a validator
+ has nominations)
  - ensure target node is removed if balance is 0 and it is a nominator.
- addresses
paritytech-secops/srlabs_findings#383

---
**Other experiments:** (not included)
- #4402 (passing the
status of the staker with who in the OnStakingUpdate interface is less
clean, it turns out)
- #4361

---------

Co-authored-by: command-bot <>

polkadot/runtime/westend/src/bag_thresholds.rs

@@ -234,7 +234,7 @@ pub const VOTER_THRESHOLDS: [u64; 200] = [
 ];
 
 /// Upper thresholds delimiting the targets bag list.
-pub const TARGET_THRESHOLDS: [crate::Balance; 200] = [
+pub const TARGET_THRESHOLDS: [u128; 200] = [
 	10_000_000_000,
 	11_131_723_507,
 	12_391_526_824,

polkadot/runtime/westend/src/lib.rs

@@ -578,7 +578,9 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 
 parameter_types! {
 	pub const VoterBagThresholds: &'static [u64] = &bag_thresholds::VOTER_THRESHOLDS;
-	pub const TargetBagThresholds: &'static [Balance] = &bag_thresholds::TARGET_THRESHOLDS;
+	pub const TargetBagThresholds: &'static [u128] = &bag_thresholds::TARGET_THRESHOLDS;
+
+	pub const VoterUpdateMode: pallet_stake_tracker::VoterUpdateMode = pallet_stake_tracker::VoterUpdateMode::Strict;
 }
 
 type VoterBagsListInstance = pallet_bags_list::Instance1;
@@ -596,16 +598,15 @@ impl pallet_bags_list::Config<TargetBagsListInstance> for Runtime {
 	type ScoreProvider = pallet_bags_list::Pallet<Runtime, TargetBagsListInstance>;
 	type WeightInfo = weights::pallet_bags_list::WeightInfo<Runtime>;
 	type BagThresholds = TargetBagThresholds;
-	type Score = Balance;
+	type Score = u128;
 }
 
 impl pallet_stake_tracker::Config for Runtime {
 	type Currency = Balances;
-	type RuntimeEvent = RuntimeEvent;
 	type Staking = Staking;
 	type VoterList = VoterList;
 	type TargetList = TargetList;
-	type WeightInfo = (); // TODO
+	type VoterUpdateMode = VoterUpdateMode;
 }
 
 pallet_staking_reward_curve::build! {
@@ -1680,7 +1681,8 @@ pub mod migrations {
 	}
 
 	/// Unreleased migrations. Add new ones here:
-	pub type Unreleased = (pallet_staking::migrations::v15::MigrateV14ToV15<Runtime>,);
+	pub type Unreleased =
+		(pallet_staking::migrations::single_block::v15::MigrateV14ToV15<Runtime>,);
 }
 
 /// Unchecked extrinsic type as expected by this runtime.

polkadot/runtime/westend/src/weights/pallet_staking.rs

@@ -826,4 +826,13 @@ impl<T: frame_system::Config> pallet_staking::WeightInfo for WeightInfo<T> {
 			.saturating_add(T::DbWeight::get().reads(5))
 			.saturating_add(T::DbWeight::get().writes(4))
 	}
+
+	// TODO: run CI bot benchmarks
+	fn drop_dangling_nomination() -> Weight {
+	    Weight::default()
+	}
+
+	fn v13_mmb_step() -> Weight {
+		Weight::default()
+	}
 }

substrate/bin/node/runtime/src/lib.rs

@@ -703,12 +703,16 @@ impl pallet_staking::Config for Runtime {
 	type DisablingStrategy = pallet_staking::UpToLimitDisablingStrategy;
 }
 
+parameter_types! {
+	pub const VoterUpdateMode: pallet_stake_tracker::VoterUpdateMode = pallet_stake_tracker::VoterUpdateMode::Strict;
+}
+
 impl pallet_stake_tracker::Config for Runtime {
 	type Currency = Balances;
-	type RuntimeEvent = RuntimeEvent;
 	type Staking = Staking;
 	type VoterList = VoterList;
 	type TargetList = TargetList;
+	type VoterUpdateMode = VoterUpdateMode;
 }
 
 impl pallet_fast_unstake::Config for Runtime {

substrate/frame/staking/src/benchmarking.rs

@@ -1212,7 +1212,7 @@ mod benchmarks {
 
 	impl_benchmark_test_suite!(
 		Staking,
-		crate::mock::ExtBuilder::default().has_stakers(true),
+		crate::mock::ExtBuilder::default().has_stakers(true).set_voter_list_lazy(),
 		crate::mock::Test,
 		exec_name = build_and_execute
 	);

substrate/frame/staking/src/migrations/v13_stake_tracker/tests.rs

@@ -135,10 +135,12 @@ fn mb_migration_target_list_dangling_validators_works() {
 }
 
 #[test]
-fn mb_migration_target_list_bench_works() {
+fn mb_migration_target_list_single_step_bench_works() {
 	ExtBuilder::default()
 		.has_stakers(false)
 		.max_winners(1000)
+		// skip checks as not all the steps are applied.
+		.stake_tracker_try_state(false)
 		.build_and_execute(|| {
 			// setup:
 			// 1000 validators;

substrate/frame/staking/src/mock.rs

@@ -362,12 +362,16 @@ impl OnStakingUpdate<AccountId, Balance> for EventTracker {
 	}
 }
 
+parameter_types! {
+	pub static VoterUpdateMode: pallet_stake_tracker::VoterUpdateMode = pallet_stake_tracker::VoterUpdateMode::Strict;
+}
+
 impl pallet_stake_tracker::Config for Test {
 	type Currency = Balances;
-	type RuntimeEvent = RuntimeEvent;
 	type Staking = Staking;
 	type VoterList = VoterBagsList;
 	type TargetList = TargetBagsList;
+	type VoterUpdateMode = VoterUpdateMode;
 }
 
 // Disabling threshold for `UpToLimitDisablingStrategy`
@@ -568,6 +572,10 @@ impl ExtBuilder {
 		SkipStakeTrackerTryStateCheck::set(!enable);
 		self
 	}
+	pub fn set_voter_list_lazy(self) -> Self {
+		VoterUpdateMode::set(pallet_stake_tracker::VoterUpdateMode::Lazy);
+		self
+	}
 	pub fn max_winners(self, max: u32) -> Self {
 		MaxWinners::set(max);
 		self
@@ -1100,6 +1108,13 @@ macro_rules! assert_session_era {
 	};
 }
 
+pub(crate) fn nominators_of(t: &AccountId) -> Vec<AccountId> {
+	Nominators::<Test>::iter()
+		.filter(|(_, n)| n.targets.contains(&t))
+		.map(|(v, _)| v)
+		.collect::<Vec<_>>()
+}
+
 pub(crate) fn staking_events() -> Vec<crate::Event<Test>> {
 	System::events()
 		.into_iter()

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

@@ -1080,8 +1080,8 @@ impl<T: Config> Pallet<T> {
 		let mut all_targets = Vec::<T::AccountId>::with_capacity(final_predicted_len as usize);
 		let mut targets_seen = 0;
 
-		// target list may contain chilled validators and dangling (i.e. unbonded) targets, filter
-		// those.
+		// target list may contain chilled validators, dangling (i.e. unbonded) targets or even
+		// nominators that have been validators - filter those out.
 		let mut targets_iter = T::TargetList::iter().filter(|t| match Self::status(&t) {
 			Ok(StakerStatus::Idle) | Ok(StakerStatus::Nominator(_)) | Err(_) => false,
 			Ok(StakerStatus::Validator) => true,

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

@@ -1094,8 +1094,6 @@ pub mod pallet {
 						.try_push(UnlockChunk { value, era })
 						.map_err(|_| Error::<T>::NoMoreChunks)?;
 				};
-				// NOTE: ledger must be updated prior to calling `Self::weight_of`.
-
 				ledger.update()?;
 
 				Self::deposit_event(Event::<T>::Unbonded { stash, amount: value });