Fix fast-unstake for accounts with slashing (#12963)

* Fix fast-unstake for accounts with slashing

* ".git/.scripts/fmt.sh" 1

* fmt

* fix

* fix weight tracking

* Adds tests for withdraw_unbonded with slashing

* Removes tests for withdraw_unbonded with slashing

* ".git/.scripts/fmt.sh"

* Adds slash spans calculation test for withdraw_unbonded

Co-authored-by: command-bot <>
Co-authored-by: gpestana <g6pestana@gmail.com>

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

@@ -1569,7 +1569,7 @@ impl<T: Config> StakingInterface for Pallet<T> {
 	}
 
 	fn force_unstake(who: Self::AccountId) -> sp_runtime::DispatchResult {
-		let num_slashing_spans = Self::slashing_spans(&who).iter().count() as u32;
+		let num_slashing_spans = Self::slashing_spans(&who).map_or(0, |s| s.iter().count() as u32);
 		Self::force_unstake(RawOrigin::Root.into(), who.clone(), num_slashing_spans)
 	}
 

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

@@ -982,7 +982,8 @@ pub mod pallet {
 			// `BondingDuration` to proceed with the unbonding.
 			let maybe_withdraw_weight = {
 				if unlocking == T::MaxUnlockingChunks::get() as usize {
-					let real_num_slashing_spans = Self::slashing_spans(&controller).iter().count();
+					let real_num_slashing_spans =
+						Self::slashing_spans(&controller).map_or(0, |s| s.iter().count());
 					Some(Self::do_withdraw_unbonded(&controller, real_num_slashing_spans as u32)?)
 				} else {
 					None

substrate/frame/staking/src/tests.rs

@@ -5725,3 +5725,54 @@ fn scale_validator_count_errors() {
 		);
 	})
 }
+
+mod staking_interface {
+	use frame_support::storage::with_storage_layer;
+	use sp_staking::StakingInterface;
+
+	use super::*;
+
+	#[test]
+	fn force_unstake_with_slash_works() {
+		ExtBuilder::default().build_and_execute(|| {
+			// without slash
+			let _ = with_storage_layer::<(), _, _>(|| {
+				// bond an account, can unstake
+				assert_eq!(Staking::bonded(&11), Some(10));
+				assert_ok!(<Staking as StakingInterface>::force_unstake(11));
+				Err(DispatchError::from("revert"))
+			});
+
+			// bond again and add a slash, still can unstake.
+			assert_eq!(Staking::bonded(&11), Some(10));
+			add_slash(&11);
+			assert_ok!(<Staking as StakingInterface>::force_unstake(11));
+		});
+	}
+
+	#[test]
+	fn do_withdraw_unbonded_with_wrong_slash_spans_works_as_expected() {
+		ExtBuilder::default().build_and_execute(|| {
+			on_offence_now(
+				&[OffenceDetails {
+					offender: (11, Staking::eras_stakers(active_era(), 11)),
+					reporters: vec![],
+				}],
+				&[Perbill::from_percent(100)],
+			);
+
+			assert_eq!(Staking::bonded(&11), Some(10));
+
+			assert_noop!(
+				Staking::withdraw_unbonded(RuntimeOrigin::signed(10), 0),
+				Error::<Test>::IncorrectSlashingSpans
+			);
+
+			let num_slashing_spans = Staking::slashing_spans(&11).map_or(0, |s| s.iter().count());
+			assert_ok!(Staking::withdraw_unbonded(
+				RuntimeOrigin::signed(10),
+				num_slashing_spans as u32
+			));
+		});
+	}
+}