Update Pallet Referenda to support Block Number Provider

cumulus/parachains/runtimes/collectives/collectives-westend/src/ambassador/mod.rs

@@ -154,6 +154,7 @@ impl pallet_referenda::Config<AmbassadorReferendaInstance> for Runtime {
 	type AlarmInterval = AlarmInterval;
 	type Tracks = tracks::TracksInfo;
 	type Preimages = Preimage;
+	type BlockNumberProvider = System;
 }
 
 parameter_types! {

cumulus/parachains/runtimes/collectives/collectives-westend/src/fellowship/mod.rs

@@ -106,6 +106,7 @@ impl pallet_referenda::Config<FellowshipReferendaInstance> for Runtime {
 	type AlarmInterval = ConstU32<1>;
 	type Tracks = tracks::TracksInfo;
 	type Preimages = Preimage;
+	type BlockNumberProvider = crate::System;
 }
 
 pub type FellowshipCollectiveInstance = pallet_ranked_collective::Instance1;

polkadot/runtime/rococo/src/governance/fellowship.rs

@@ -308,6 +308,7 @@ impl pallet_referenda::Config<FellowshipReferendaInstance> for Runtime {
 	type AlarmInterval = AlarmInterval;
 	type Tracks = TracksInfo;
 	type Preimages = Preimage;
+	type BlockNumberProvider = System;
 }
 
 pub type FellowshipCollectiveInstance = pallet_ranked_collective::Instance1;

polkadot/runtime/rococo/src/governance/mod.rs

@@ -90,4 +90,5 @@ impl pallet_referenda::Config for Runtime {
 	type AlarmInterval = AlarmInterval;
 	type Tracks = TracksInfo;
 	type Preimages = Preimage;
+	type BlockNumberProvider = System;
 }

polkadot/runtime/westend/src/governance/mod.rs

@@ -94,4 +94,5 @@ impl pallet_referenda::Config for Runtime {
 	type AlarmInterval = AlarmInterval;
 	type Tracks = TracksInfo;
 	type Preimages = Preimage;
+	type BlockNumberProvider = System;
 }

prdoc/pr_6338.prdoc

@@ -0,0 +1,14 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Update Referenda to Support Block Number Provider
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      This PR makes the referenda pallet uses the relay chain as a block provider for a parachain on a regular schedule.
+      To migrate existing referenda implementations, simply add `type BlockNumberProvider = System` to have the same behavior as before.
+
+crates:
+- name: pallet-referenda
+  bump: minor

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

@@ -1005,6 +1005,7 @@ impl pallet_referenda::Config for Runtime {
 	type AlarmInterval = AlarmInterval;
 	type Tracks = TracksInfo;
 	type Preimages = Preimage;
+	type BlockNumberProvider = System;
 }
 
 impl pallet_referenda::Config<pallet_referenda::Instance2> for Runtime {
@@ -1025,6 +1026,7 @@ impl pallet_referenda::Config<pallet_referenda::Instance2> for Runtime {
 	type AlarmInterval = AlarmInterval;
 	type Tracks = TracksInfo;
 	type Preimages = Preimage;
+	type BlockNumberProvider = System;
 }
 
 impl pallet_ranked_collective::Config for Runtime {

substrate/frame/referenda/src/benchmarking.rs

@@ -33,6 +33,10 @@ use sp_runtime::traits::Bounded as ArithBounded;
 
 const SEED: u32 = 0;
 
+fn set_block_number<T: Config<I>, I: 'static>(n: BlockNumberFor<T>) {
+	<T as Config<I>>::BlockNumberProvider::set_block_number(n);
+}
+
 fn assert_last_event<T: Config<I>, I: 'static>(generic_event: <T as Config<I>>::RuntimeEvent) {
 	frame_system::Pallet::<T>::assert_last_event(generic_event.into());
 }
@@ -151,25 +155,25 @@ fn make_failing<T: Config<I>, I: 'static>(index: ReferendumIndex) {
 fn skip_prepare_period<T: Config<I>, I: 'static>(index: ReferendumIndex) {
 	let status = Referenda::<T, I>::ensure_ongoing(index).unwrap();
 	let prepare_period_over = status.submitted + info::<T, I>(index).prepare_period;
-	frame_system::Pallet::<T>::set_block_number(prepare_period_over);
+	set_block_number::<T, I>(prepare_period_over);
 }
 
 fn skip_decision_period<T: Config<I>, I: 'static>(index: ReferendumIndex) {
 	let status = Referenda::<T, I>::ensure_ongoing(index).unwrap();
 	let decision_period_over = status.deciding.unwrap().since + info::<T, I>(index).decision_period;
-	frame_system::Pallet::<T>::set_block_number(decision_period_over);
+	set_block_number::<T, I>(decision_period_over);
 }
 
 fn skip_confirm_period<T: Config<I>, I: 'static>(index: ReferendumIndex) {
 	let status = Referenda::<T, I>::ensure_ongoing(index).unwrap();
 	let confirm_period_over = status.deciding.unwrap().confirming.unwrap();
-	frame_system::Pallet::<T>::set_block_number(confirm_period_over);
+	set_block_number::<T, I>(confirm_period_over);
 }
 
 fn skip_timeout_period<T: Config<I>, I: 'static>(index: ReferendumIndex) {
 	let status = Referenda::<T, I>::ensure_ongoing(index).unwrap();
 	let timeout_period_over = status.submitted + T::UndecidingTimeout::get();
-	frame_system::Pallet::<T>::set_block_number(timeout_period_over);
+	set_block_number::<T, I>(timeout_period_over);
 }
 
 fn alarm_time<T: Config<I>, I: 'static>(

substrate/frame/referenda/src/lib.rs

@@ -105,6 +105,7 @@ pub use self::{
 	},
 	weights::WeightInfo,
 };
+use sp_runtime::traits::BlockNumberProvider;
 pub use alloc::vec::Vec;
 
 #[cfg(test)]
@@ -239,6 +240,9 @@ pub mod pallet {
 
 		/// The preimage provider.
 		type Preimages: QueryPreimage<H = Self::Hashing> + StorePreimage;
+
+		/// Provider for the block number. Normally this is the `frame_system` pallet.
+		type BlockNumberProvider: BlockNumberProvider<BlockNumber = BlockNumberFor<Self>>;
 	}
 
 	/// The next free referendum index, aka the number of referenda started so far.
@@ -485,7 +489,7 @@ pub mod pallet {
 				*x += 1;
 				r
 			});
-			let now = frame_system::Pallet::<T>::block_number();
+			let now = T::BlockNumberProvider::current_block_number();
 			let nudge_call =
 				T::Preimages::bound(CallOf::<T, I>::from(Call::nudge_referendum { index }))?;
 			let status = ReferendumStatus {
@@ -527,7 +531,7 @@ pub mod pallet {
 			let track = Self::track(status.track).ok_or(Error::<T, I>::NoTrack)?;
 			status.decision_deposit =
 				Some(Self::take_deposit(who.clone(), track.decision_deposit)?);
-			let now = frame_system::Pallet::<T>::block_number();
+			let now = T::BlockNumberProvider::current_block_number();
 			let (info, _, branch) = Self::service_referendum(now, index, status);
 			ReferendumInfoFor::<T, I>::insert(index, info);
 			let e =
@@ -584,7 +588,7 @@ pub mod pallet {
 			Self::note_one_fewer_deciding(status.track);
 			Self::deposit_event(Event::<T, I>::Cancelled { index, tally: status.tally });
 			let info = ReferendumInfo::Cancelled(
-				frame_system::Pallet::<T>::block_number(),
+				T::BlockNumberProvider::current_block_number(),
 				Some(status.submission_deposit),
 				status.decision_deposit,
 			);
@@ -611,7 +615,7 @@ pub mod pallet {
 			Self::slash_deposit(Some(status.submission_deposit.clone()));
 			Self::slash_deposit(status.decision_deposit.clone());
 			Self::do_clear_metadata(index);
-			let info = ReferendumInfo::Killed(frame_system::Pallet::<T>::block_number());
+			let info = ReferendumInfo::Killed(T::BlockNumberProvider::current_block_number());
 			ReferendumInfoFor::<T, I>::insert(index, info);
 			Ok(())
 		}
@@ -627,7 +631,7 @@ pub mod pallet {
 			index: ReferendumIndex,
 		) -> DispatchResultWithPostInfo {
 			ensure_root(origin)?;
-			let now = frame_system::Pallet::<T>::block_number();
+			let now = T::BlockNumberProvider::current_block_number();
 			let mut status = Self::ensure_ongoing(index)?;
 			// This is our wake-up, so we can disregard the alarm.
 			status.alarm = None;
@@ -658,7 +662,7 @@ pub mod pallet {
 			let mut track_queue = TrackQueue::<T, I>::get(track);
 			let branch =
 				if let Some((index, mut status)) = Self::next_for_deciding(&mut track_queue) {
-					let now = frame_system::Pallet::<T>::block_number();
+					let now = T::BlockNumberProvider::current_block_number();
 					let (maybe_alarm, branch) =
 						Self::begin_deciding(&mut status, index, now, track_info);
 					if let Some(set_alarm) = maybe_alarm {
@@ -758,7 +762,7 @@ impl<T: Config<I>, I: 'static> Polling<T::Tally> for Pallet<T, I> {
 		match ReferendumInfoFor::<T, I>::get(index) {
 			Some(ReferendumInfo::Ongoing(mut status)) => {
 				let result = f(PollStatus::Ongoing(&mut status.tally, status.track));
-				let now = frame_system::Pallet::<T>::block_number();
+				let now = T::BlockNumberProvider::current_block_number();
 				Self::ensure_alarm_at(&mut status, index, now + One::one());
 				ReferendumInfoFor::<T, I>::insert(index, ReferendumInfo::Ongoing(status));
 				result
@@ -778,7 +782,7 @@ impl<T: Config<I>, I: 'static> Polling<T::Tally> for Pallet<T, I> {
 		match ReferendumInfoFor::<T, I>::get(index) {
 			Some(ReferendumInfo::Ongoing(mut status)) => {
 				let result = f(PollStatus::Ongoing(&mut status.tally, status.track))?;
-				let now = frame_system::Pallet::<T>::block_number();
+				let now = T::BlockNumberProvider::current_block_number();
 				Self::ensure_alarm_at(&mut status, index, now + One::one());
 				ReferendumInfoFor::<T, I>::insert(index, ReferendumInfo::Ongoing(status));
 				Ok(result)
@@ -800,7 +804,7 @@ impl<T: Config<I>, I: 'static> Polling<T::Tally> for Pallet<T, I> {
 			*x += 1;
 			r
 		});
-		let now = frame_system::Pallet::<T>::block_number();
+		let now = T::BlockNumberProvider::current_block_number();
 		let dummy_account_id =
 			codec::Decode::decode(&mut sp_runtime::traits::TrailingZeroInput::new(&b"dummy"[..]))
 				.expect("infinite length input; no invalid inputs for type; qed");
@@ -828,7 +832,7 @@ impl<T: Config<I>, I: 'static> Polling<T::Tally> for Pallet<T, I> {
 		let mut status = Self::ensure_ongoing(index).map_err(|_| ())?;
 		Self::ensure_no_alarm(&mut status);
 		Self::note_one_fewer_deciding(status.track);
-		let now = frame_system::Pallet::<T>::block_number();
+		let now = T::BlockNumberProvider::current_block_number();
 		let info = if approved {
 			ReferendumInfo::Approved(now, Some(status.submission_deposit), status.decision_deposit)
 		} else {
@@ -868,7 +872,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 			ReferendumInfo::Ongoing(status) => {
 				let track = Self::track(status.track).ok_or(Error::<T, I>::NoTrack)?;
 				let elapsed = if let Some(deciding) = status.deciding {
-					frame_system::Pallet::<T>::block_number().saturating_sub(deciding.since)
+					T::BlockNumberProvider::current_block_number().saturating_sub(deciding.since)
 				} else {
 					Zero::zero()
 				};
@@ -893,7 +897,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		origin: PalletsOriginOf<T>,
 		call: BoundedCallOf<T, I>,
 	) {
-		let now = frame_system::Pallet::<T>::block_number();
+		let now = T::BlockNumberProvider::current_block_number();
 		// Earliest allowed block is always at minimum the next block.
 		let earliest_allowed = now.saturating_add(track.min_enactment_period.max(One::one()));
 		let desired = desired.evaluate(now);
@@ -931,7 +935,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 			result.is_ok(),
 			"Unable to schedule a new alarm at #{:?} (now: #{:?}), scheduler error: `{:?}`",
 			when,
-			frame_system::Pallet::<T>::block_number(),
+			T::BlockNumberProvider::current_block_number(),
 			result.unwrap_err(),
 		);
 		result.ok().map(|x| (when, x))
@@ -1023,7 +1027,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 	/// overall more efficient), however the weights become rather less easy to measure.
 	fn note_one_fewer_deciding(track: TrackIdOf<T, I>) {
 		// Set an alarm call for the next block to nudge the track along.
-		let now = frame_system::Pallet::<T>::block_number();
+		let now = T::BlockNumberProvider::current_block_number();
 		let next_block = now + One::one();
 		let call = match T::Preimages::bound(CallOf::<T, I>::from(Call::one_fewer_deciding {
 			track,

substrate/frame/referenda/src/mock.rs

@@ -206,6 +206,7 @@ impl Config for Test {
 	type AlarmInterval = AlarmInterval;
 	type Tracks = TestTracksInfo;
 	type Preimages = Preimage;
+	type BlockNumberProvider = System;
 }
 pub struct ExtBuilder {}