[NPoS] Check if staker is exposed in paged exposure storage entries

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

@@ -794,7 +794,7 @@ impl<T: Config> Pallet<T> {
 		stash: T::AccountId,
 		exposure: Exposure<T::AccountId, BalanceOf<T>>,
 	) {
-		<ErasStakers<T>>::insert(&current_era, &stash, &exposure);
+		EraInfo::<T>::set_exposure(current_era, &stash, exposure);
 	}
 
 	#[cfg(feature = "runtime-benchmarks")]
@@ -1745,9 +1745,16 @@ impl<T: Config> StakingInterface for Pallet<T> {
 	}
 
 	fn is_exposed_in_era(who: &Self::AccountId, era: &EraIndex) -> bool {
+		// look in the non paged exposures
+		// FIXME: Can be cleaned up once non paged exposures are cleared (https://github.com/paritytech/polkadot-sdk/issues/433)
 		ErasStakers::<T>::iter_prefix(era).any(|(validator, exposures)| {
 			validator == *who || exposures.others.iter().any(|i| i.who == *who)
 		})
+			||
+		// look in the paged exposures
+		ErasStakersPaged::<T>::iter_prefix((era,)).any(|((validator, _), exposure_page)| {
+			validator == *who || exposure_page.others.iter().any(|i| i.who == *who)
+		})
 	}
 	fn status(
 		who: &Self::AccountId,
@@ -1812,6 +1819,7 @@ impl<T: Config> Pallet<T> {
 
 		Self::check_nominators()?;
 		Self::check_exposures()?;
+		Self::check_paged_exposures()?;
 		Self::check_ledgers()?;
 		Self::check_count()
 	}
@@ -1860,6 +1868,70 @@ impl<T: Config> Pallet<T> {
 			.collect::<Result<(), TryRuntimeError>>()
 	}
 
+	fn check_paged_exposures() -> Result<(), TryRuntimeError> {
+		use sp_std::collections::btree_map::BTreeMap;
+		use sp_staking::PagedExposureMetadata;
+
+		// Sanity check for the paged exposure of the active era.
+		let mut exposures: BTreeMap<T::AccountId, PagedExposureMetadata<BalanceOf<T>>> =
+			BTreeMap::new();
+		let era = Self::active_era().unwrap().index;
+		let accumulator_default = PagedExposureMetadata {
+			total: Zero::zero(),
+			own: Zero::zero(),
+			nominator_count: 0,
+			page_count: 0,
+		};
+
+		ErasStakersPaged::<T>::iter_prefix((era,))
+			.map(|((validator, _page), expo)| {
+				ensure!(
+					expo.page_total ==
+						expo.others.iter().map(|e| e.value).fold(Zero::zero(), |acc, x| acc + x),
+					"wrong total exposure for the page.",
+				);
+
+				let metadata = exposures.get(&validator).unwrap_or(&accumulator_default);
+				exposures.insert(
+					validator,
+					PagedExposureMetadata {
+						total: metadata.total + expo.page_total,
+						own: metadata.own,
+						nominator_count: metadata.nominator_count + expo.others.len() as u32,
+						page_count: metadata.page_count + 1,
+					},
+				);
+
+				Ok(())
+			})
+			.collect::<Result<(), TryRuntimeError>>()?;
+
+		exposures
+			.iter()
+			.map(|(validator, metadata)| {
+				let actual_overview = ErasStakersOverview::<T>::get(era, validator);
+
+				ensure!(actual_overview.is_some(), "No overview found for a paged exposure");
+				let actual_overview = actual_overview.unwrap();
+
+				ensure!(
+					actual_overview.total == metadata.total + actual_overview.own,
+					"Exposure metadata does not have correct total exposed stake."
+				);
+				ensure!(
+					actual_overview.nominator_count == metadata.nominator_count,
+					"Exposure metadata does not have correct count of nominators."
+				);
+				ensure!(
+					actual_overview.page_count == metadata.page_count,
+					"Exposure metadata does not have correct count of pages."
+				);
+
+				Ok(())
+			})
+			.collect::<Result<(), TryRuntimeError>>()
+	}
+
 	fn check_nominators() -> Result<(), TryRuntimeError> {
 		// a check per nominator to ensure their entire stake is correctly distributed. Will only
 		// kick-in if the nomination was submitted before the current era.

substrate/frame/staking/src/tests.rs

@@ -6637,6 +6637,14 @@ fn test_validator_exposure_is_backward_compatible_with_non_paged_rewards_payout(
 		);
 		assert_eq!(EraInfo::<Test>::get_page_count(1, &11), 2);
 
+		// validator is exposed
+		assert!(<Staking as sp_staking::StakingInterface>::is_exposed_in_era(&11, &1));
+		// nominators are exposed
+		for i in 10..15 {
+			let who: AccountId = 1000 + i;
+			assert!(<Staking as sp_staking::StakingInterface>::is_exposed_in_era(&who, &1));
+		}
+
 		// case 2: exposure exist in ErasStakers and ErasStakersClipped (legacy).
 		// delete paged storage and add exposure to clipped storage
 		<ErasStakersPaged<Test>>::remove((1, 11, 0));
@@ -6672,6 +6680,14 @@ fn test_validator_exposure_is_backward_compatible_with_non_paged_rewards_payout(
 		assert_eq!(actual_exposure_full.own, 1000);
 		assert_eq!(actual_exposure_full.total, total_exposure);
 
+		// validator is exposed
+		assert!(<Staking as sp_staking::StakingInterface>::is_exposed_in_era(&11, &1));
+		// nominators are exposed
+		for i in 10..15 {
+			let who: AccountId = 1000 + i;
+			assert!(<Staking as sp_staking::StakingInterface>::is_exposed_in_era(&who, &1));
+		}
+
 		// for pages other than 0, clipped storage returns empty exposure
 		assert_eq!(EraInfo::<Test>::get_paged_exposure(1, &11, 1), None);
 		// page size is 1 for clipped storage