Quick and dirty fixes to get rid of the compilation errors (TODOs added)

polkadot/runtime/westend/src/lib.rs

@@ -763,7 +763,7 @@ impl pallet_staking::Config for Runtime {
 	type BondingDuration = BondingDuration;
 	type SlashDeferDuration = SlashDeferDuration;
 	type AdminOrigin = EitherOf<EnsureRoot<AccountId>, StakingAdmin>;
-	type SessionInterface = Self;
+	type SessionInterface = (); // Should be pallet_staking_rc_client on ah-next
 	type EraPayout = EraPayout;
 	type MaxExposurePageSize = MaxExposurePageSize;
 	type NextNewSession = Session;

substrate/frame/staking/ah-client/src/lib.rs

@@ -154,9 +154,19 @@ pub mod pallet {
 		fn new_session(
 			_: sp_staking::SessionIndex,
 		) -> Option<Vec<(<T as frame_system::Config>::AccountId, ())>> {
-			// If there is a new validator set - return it. Otherwise return `None`.
-			ValidatorSet::<T>::take()
-				.map(|validators| validators.into_iter().map(|v| (v, ())).collect())
+			let maybe_new_validator_set = ValidatorSet::<T>::take()
+				.map(|validators| validators.into_iter().map(|v| (v, ())).collect());
+
+			// A new validator set is an indication for a new era. Clear
+			if maybe_new_validator_set.is_none() {
+				// TODO: historical sessions should be pruned. This used to happen after the bonding
+				// period for the session but it would be nice to avoid XCM messages for prunning
+				// and trigger it from RC directly.
+
+				// <pallet_session::historical::Pallet<T>>::prune_up_to(up_to); // TODO!!!
+			}
+
+			return maybe_new_validator_set
 		}
 
 		fn new_session_genesis(

substrate/frame/staking/rc-client/src/lib.rs

@@ -53,6 +53,21 @@ pub trait StakingApi {
 	fn reward_by_ids(validators_points: Vec<(AccountId32, u32)>);
 }
 
+// TODO: update the comment
+/// Means for interacting with a specialized version of the `session` trait.
+///
+/// This is needed because `Staking` sets the `ValidatorIdOf` of the `pallet_session::Config`
+pub trait SessionInterface<AccountId> {
+	/// Get the validators from session.
+	fn validators() -> Vec<AccountId>;
+}
+
+impl<AccountId> SessionInterface<AccountId> for () {
+	fn validators() -> Vec<AccountId> {
+		Vec::new()
+	}
+}
+
 /// `pallet-staking-ah-client` pallet index on Relay chain. Used to construct remote calls.
 ///
 /// The codec index must correspond to the index of `pallet-staking-ah-client` in the
@@ -188,6 +203,13 @@ pub mod pallet {
 		}
 	}
 
+	impl<T: Config> SessionInterface<T::AccountId> for Pallet<T> {
+		fn validators() -> Vec<T::AccountId> {
+			// TODO: cache the last applied validator set and return it here
+			vec![]
+		}
+	}
+
 	fn mk_relay_chain_call(call: SessionCalls) -> Instruction<()> {
 		Instruction::Transact {
 			origin_kind: OriginKind::Superuser,

substrate/frame/staking/src/lib.rs

@@ -976,31 +976,6 @@ impl<Balance, const MAX: u32> NominationsQuota<Balance> for FixedNominationsQuot
 	}
 }
 
-/// Means for interacting with a specialized version of the `session` trait.
-///
-/// This is needed because `Staking` sets the `ValidatorIdOf` of the `pallet_session::Config`
-pub trait SessionInterface<AccountId> {
-	/// Report an offending validator.
-	fn report_offence(validator: AccountId, severity: OffenceSeverity);
-	/// Get the validators from session.
-	fn validators() -> Vec<AccountId>;
-	/// Prune historical session tries up to but not including the given index.
-	fn prune_historical_up_to(up_to: SessionIndex);
-}
-
-// TODO: Why we need this?
-impl<AccountId> SessionInterface<AccountId> for () {
-	fn report_offence(_validator: AccountId, _severity: OffenceSeverity) {
-		()
-	}
-	fn validators() -> Vec<AccountId> {
-		Vec::new()
-	}
-	fn prune_historical_up_to(_: SessionIndex) {
-		()
-	}
-}
-
 /// Handler for determining how much of a balance should be paid out on the current era.
 pub trait EraPayout<Balance> {
 	/// Determine the payout for this era.

substrate/frame/staking/src/migrations.rs

@@ -264,6 +264,7 @@ pub mod v16 {
 /// Migrating `OffendingValidators` from `Vec<(u32, bool)>` to `Vec<u32>`
 pub mod v15 {
 	use super::*;
+	use pallet_staking_rc_client::SessionInterface;
 
 	// The disabling strategy used by staking pallet
 	type DefaultDisablingStrategy = pallet_session::disabling::UpToLimitDisablingStrategy;

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

@@ -32,7 +32,7 @@ use frame_support::{
 	weights::Weight,
 };
 use frame_system::{pallet_prelude::BlockNumberFor, RawOrigin};
-use pallet_staking_rc_client::{Offence, StakingApi};
+use pallet_staking_rc_client::{Offence, SessionInterface, StakingApi};
 use sp_core::crypto::AccountId32;
 use sp_runtime::{
 	traits::{Bounded, CheckedAdd, Convert, SaturatedConversion, Saturating, StaticLookup, Zero},
@@ -50,8 +50,8 @@ use crate::{
 	asset, election_size_tracker::StaticTracker, log, slashing, weights::WeightInfo, ActiveEraInfo,
 	BalanceOf, BoundedExposuresOf, EraInfo, EraPayout, Exposure, Forcing, IndividualExposure,
 	LedgerIntegrityState, MaxNominationsOf, MaxWinnersOf, MaxWinnersPerPageOf, Nominations,
-	NominationsQuota, PositiveImbalanceOf, RewardDestination, SessionInterface, SnapshotStatus,
-	StakingLedger, ValidatorPrefs, STAKING_ID,
+	NominationsQuota, PositiveImbalanceOf, RewardDestination, SnapshotStatus, StakingLedger,
+	ValidatorPrefs, STAKING_ID,
 };
 use alloc::{boxed::Box, vec, vec::Vec};
 
@@ -573,9 +573,10 @@ impl<T: Config> Pallet<T> {
 					slashing::clear_era_metadata::<T>(pruned_era);
 				}
 
-				if let Some(&(_, first_session)) = bonded.first() {
-					T::SessionInterface::prune_historical_up_to(first_session);
-				}
+				// TODO: should be handled in ah_client (see the comment there)
+				// if let Some(&(_, first_session)) = bonded.first() {
+				// 	T::SessionInterface::prune_historical_up_to(first_session);
+				// }
 			}
 		});
 	}
@@ -1713,8 +1714,7 @@ where
 			}
 
 			add_db_reads_writes(1, 0);
-			let Some(exposure_overview) =
-				<ErasStakersOverview<T>>::get(&offence_era, &validator)
+			let Some(exposure_overview) = <ErasStakersOverview<T>>::get(&offence_era, &validator)
 			else {
 				// defensive: this implies offence is for a discarded era, and should already be
 				// filtered out.
@@ -1733,19 +1733,19 @@ where
 				offence_era,
 			});
 
-			if offence_era == active_era.index {
-				// offence is in the current active era. Report it to session to maybe disable the
-				// validator.
-				add_db_reads_writes(2, 2);
-				T::SessionInterface::report_offence(
-					validator.clone(),
-					OffenceSeverity(slash_fraction),
-				);
-			}
+			// TODO: handled in ah_client. Verify it works correctly before removing the commented
+			// out code. if offence_era == active_era.index {
+			// 	// offence is in the current active era. Report it to session to maybe disable the
+			// 	// validator.
+			// 	add_db_reads_writes(2, 2);
+			// 	T::SessionInterface::report_offence(
+			// 		validator.clone(),
+			// 		OffenceSeverity(slash_fraction),
+			// 	);
+			// }
 			add_db_reads_writes(1, 0);
-			let prior_slash_fraction =
-				ValidatorSlashInEra::<T>::get(offence_era, &validator)
-					.map_or(Zero::zero(), |(f, _)| f);
+			let prior_slash_fraction = ValidatorSlashInEra::<T>::get(offence_era, &validator)
+				.map_or(Zero::zero(), |(f, _)| f);
 
 			add_db_reads_writes(1, 0);
 			if let Some(existing) = OffenceQueue::<T>::get(offence_era, &validator) {
@@ -1873,8 +1873,6 @@ where
 // 	}
 // }
 
-
-
 impl<T: Config> ScoreProvider<T::AccountId> for Pallet<T> {
 	type Score = VoteWeight;
 

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

@@ -35,6 +35,7 @@ use frame_support::{
 	BoundedBTreeSet, BoundedVec,
 };
 use frame_system::{ensure_root, ensure_signed, pallet_prelude::*};
+use pallet_staking_rc_client::SessionInterface;
 use rand::seq::SliceRandom;
 use rand_chacha::{
 	rand_core::{RngCore, SeedableRng},
@@ -60,7 +61,7 @@ use crate::{
 	asset, slashing, weights::WeightInfo, AccountIdLookupOf, ActiveEraInfo, BalanceOf, EraPayout,
 	EraRewardPoints, ExposurePage, Forcing, LedgerIntegrityState, MaxNominationsOf,
 	NegativeImbalanceOf, Nominations, NominationsQuota, PositiveImbalanceOf, RewardDestination,
-	SessionInterface, StakingLedger, UnappliedSlash, UnlockChunk, ValidatorPrefs,
+	StakingLedger, UnappliedSlash, UnlockChunk, ValidatorPrefs,
 };
 
 // The speculative number of spans are used as an input of the weight annotation of