Properly defer slashes

frame/staking/src/pallet/impls.rs

@@ -32,7 +32,7 @@ use frame_support::{
 use frame_system::{pallet_prelude::BlockNumberFor, RawOrigin};
 use pallet_session::historical;
 use sp_runtime::{
-	traits::{Bounded, Convert, SaturatedConversion, Saturating, StaticLookup, Zero},
+	traits::{Bounded, Convert, SaturatedConversion, Saturating, StaticLookup, Zero, One},
 	Perbill,
 };
 use sp_staking::{
@@ -599,18 +599,16 @@ impl<T: Config> Pallet<T> {
 
 	/// Apply previously-unapplied slashes on the beginning of a new era, after a delay.
 	fn apply_unapplied_slashes(active_era: EraIndex) {
-		if <Self as Store>::UnappliedSlashes::contains_key(&active_era) {
-			let era_slashes = <Self as Store>::UnappliedSlashes::take(&active_era);
-			log!(
-				debug,
-				"found {} slashes scheduled to be executed in era {}",
-				active_era,
-				era_slashes.len()
-			);
-			for slash in era_slashes {
-				let slash_era = active_era.saturating_sub(T::SlashDeferDuration::get());
-				slashing::apply_slash::<T>(slash, slash_era);
-			}
+		let era_slashes = <Self as Store>::UnappliedSlashes::take(&active_era);
+		log!(
+			debug,
+			"found {} slashes scheduled to be executed in era {:?}",
+			era_slashes.len(),
+			active_era,
+		);
+		for slash in era_slashes {
+			let slash_era = active_era.saturating_sub(T::SlashDeferDuration::get());
+			slashing::apply_slash::<T>(slash, slash_era);
 		}
 	}
 
@@ -1266,7 +1264,7 @@ where
 						slash_era + slash_defer_duration + 1,
 					);
 					<Self as Store>::UnappliedSlashes::mutate(
-						slash_era + slash_defer_duration + 1,
+						slash_era.saturating_add(slash_defer_duration).saturating_add(One::one()),
 						move |for_later| for_later.push(unapplied),
 					);
 					add_db_reads_writes(1, 1);

frame/staking/src/pallet/mod.rs

@@ -477,10 +477,6 @@ pub mod pallet {
 		ValueQuery,
 	>;
 
-	/// The earliest era for which we have a pending, unapplied slash.
-	#[pallet::storage]
-	pub(crate) type EarliestUnappliedSlash<T> = StorageValue<_, EraIndex>;
-
 	/// The last planned session scheduled by the session pallet.
 	///
 	/// This is basically in sync with the call to [`pallet_session::SessionManager::new_session`].

frame/staking/src/tests.rs

@@ -2778,7 +2778,7 @@ fn deferred_slashes_are_deferred() {
 		assert_eq!(Balances::free_balance(11), 1000);
 		assert_eq!(Balances::free_balance(101), 2000);
 
-		let _ = staking_events_since_last_call();
+		System::reset_events();
 
 		// at the start of era 4, slashes from era 1 are processed,
 		// after being deferred for at least 2 full eras.
@@ -2814,7 +2814,7 @@ fn retroactive_deferred_slashes_two_eras_before_() {
 			1, // should be deferred for two full eras, and applied at the beginning of era 4.
 			DisableStrategy::Never,
 		);
-		let _ = staking_events_since_last_call();
+		System::reset_events();
 
 		mock::start_active_era(4);
 
@@ -2838,14 +2838,17 @@ fn retroactive_deferred_slashes_one_before() {
 		mock::start_active_era(1);
 		let exposure_11_at_era1 = Staking::eras_stakers(active_era(), 11);
 
+		mock::start_active_era(2);
+
+
 		mock::start_active_era(3);
 		on_offence_in_era(
 			&[OffenceDetails { offender: (11, exposure_11_at_era1), reporters: vec![] }],
 			&[Perbill::from_percent(10)],
 			2, // should be deferred for two full eras, and applied at the beginning of era 5.
 			DisableStrategy::Never,
 		);
-		let _ = staking_events_since_last_call();
+		System::reset_events();
 
 		mock::start_active_era(4);
 		assert_eq!(
@@ -2989,7 +2992,7 @@ fn remove_deferred() {
 
 		// at the start of era 4, slashes from era 1 are processed,
 		// after being deferred for at least 2 full eras.
-		let _ = staking_events_since_last_call();
+		System::reset_events();
 		mock::start_active_era(4);
 
 		// the first slash for 10% was cancelled, but the 15% one