Deduplicate Grandpa consensus log reading logic (#2245) (#2246)

bridges/modules/grandpa/src/lib.rs

@@ -39,13 +39,12 @@
 pub use storage_types::StoredAuthoritySet;
 
 use bp_header_chain::{
-	justification::GrandpaJustification, ChainWithGrandpa, HeaderChain, InitializationData,
+	justification::GrandpaJustification, ChainWithGrandpa, GrandpaConsensusLogReader, HeaderChain,
-	StoredHeaderData, StoredHeaderDataBuilder,
+	InitializationData, StoredHeaderData, StoredHeaderDataBuilder,
 };
 use bp_runtime::{BlockNumberOf, HashOf, HasherOf, HeaderId, HeaderOf, OwnedBridgeModule};
 use finality_grandpa::voter_set::VoterSet;
 use frame_support::{dispatch::PostDispatchInfo, ensure, DefaultNoBound};
-use sp_consensus_grandpa::{ConsensusLog, GRANDPA_ENGINE_ID};
 use sp_runtime::{
 	traits::{Header as HeaderT, Zero},
 	SaturatedConversion,
@@ -443,11 +442,17 @@ pub mod pallet {
 
 		// We don't support forced changes - at that point governance intervention is required.
 		ensure!(
-			super::find_forced_change(header).is_none(),
+			GrandpaConsensusLogReader::<BridgedBlockNumber<T, I>>::find_forced_change(
+				header.digest()
+			)
+			.is_none(),
 			<Error<T, I>>::UnsupportedScheduledChange
 		);
 
-		if let Some(change) = super::find_scheduled_change(header) {
+		if let Some(change) =
+			GrandpaConsensusLogReader::<BridgedBlockNumber<T, I>>::find_scheduled_change(
+				header.digest(),
+			) {
 			// GRANDPA only includes a `delay` for forced changes, so this isn't valid.
 			ensure!(change.delay == Zero::zero(), <Error<T, I>>::UnsupportedScheduledChange);
 
@@ -616,42 +621,6 @@ impl<T: Config<I>, I: 'static> HeaderChain<BridgedChain<T, I>> for GrandpaChainH
 	}
 }
 
-pub(crate) fn find_scheduled_change<H: HeaderT>(
-	header: &H,
-) -> Option<sp_consensus_grandpa::ScheduledChange<H::Number>> {
-	use sp_runtime::generic::OpaqueDigestItemId;
-
-	let id = OpaqueDigestItemId::Consensus(&GRANDPA_ENGINE_ID);
-
-	let filter_log = |log: ConsensusLog<H::Number>| match log {
-		ConsensusLog::ScheduledChange(change) => Some(change),
-		_ => None,
-	};
-
-	// find the first consensus digest with the right ID which converts to
-	// the right kind of consensus log.
-	header.digest().convert_first(|l| l.try_to(id).and_then(filter_log))
-}
-
-/// Checks the given header for a consensus digest signaling a **forced** scheduled change and
-/// extracts it.
-pub(crate) fn find_forced_change<H: HeaderT>(
-	header: &H,
-) -> Option<(H::Number, sp_consensus_grandpa::ScheduledChange<H::Number>)> {
-	use sp_runtime::generic::OpaqueDigestItemId;
-
-	let id = OpaqueDigestItemId::Consensus(&GRANDPA_ENGINE_ID);
-
-	let filter_log = |log: ConsensusLog<H::Number>| match log {
-		ConsensusLog::ForcedChange(delay, change) => Some((delay, change)),
-		_ => None,
-	};
-
-	// find the first consensus digest with the right ID which converts to
-	// the right kind of consensus log.
-	header.digest().convert_first(|l| l.try_to(id).and_then(filter_log))
-}
-
 /// (Re)initialize bridge with given header for using it in `pallet-bridge-messages` benchmarks.
 #[cfg(feature = "runtime-benchmarks")]
 pub fn initialize_for_benchmarks<T: Config<I>, I: 'static>(header: BridgedHeader<T, I>) {
@@ -685,6 +654,7 @@ mod tests {
 		storage::generator::StorageValue,
 	};
 	use frame_system::{EventRecord, Phase};
+	use sp_consensus_grandpa::{ConsensusLog, GRANDPA_ENGINE_ID};
 	use sp_core::Get;
 	use sp_runtime::{Digest, DigestItem, DispatchError};
 

bridges/primitives/header-chain/src/lib.rs

@@ -139,7 +139,7 @@ pub trait ConsensusLogReader {
 pub struct GrandpaConsensusLogReader<Number>(sp_std::marker::PhantomData<Number>);
 
 impl<Number: Codec> GrandpaConsensusLogReader<Number> {
-	pub fn find_authorities_change(
+	pub fn find_scheduled_change(
 		digest: &Digest,
 	) -> Option<sp_consensus_grandpa::ScheduledChange<Number>> {
 		// find the first consensus digest with the right ID which converts to
@@ -151,11 +151,24 @@ impl<Number: Codec> GrandpaConsensusLogReader<Number> {
 				_ => None,
 			})
 	}
+
+	pub fn find_forced_change(
+		digest: &Digest,
+	) -> Option<(Number, sp_consensus_grandpa::ScheduledChange<Number>)> {
+		// find the first consensus digest with the right ID which converts to
+		// the right kind of consensus log.
+		digest
+			.convert_first(|log| log.consensus_try_to(&GRANDPA_ENGINE_ID))
+			.and_then(|log| match log {
+				ConsensusLog::ForcedChange(delay, change) => Some((delay, change)),
+				_ => None,
+			})
+	}
 }
 
 impl<Number: Codec> ConsensusLogReader for GrandpaConsensusLogReader<Number> {
 	fn schedules_authorities_change(digest: &Digest) -> bool {
-		GrandpaConsensusLogReader::<Number>::find_authorities_change(digest).is_some()
+		GrandpaConsensusLogReader::<Number>::find_scheduled_change(digest).is_some()
 	}
 }
 

bridges/relays/lib-substrate-relay/src/finality/engine.rs

@@ -237,10 +237,9 @@ impl<C: ChainWithGrandpa> Engine<C> for Grandpa<C> {
 		// If initial header changes the GRANDPA authorities set, then we need previous authorities
 		// to verify justification.
 		let mut authorities_for_verification = initial_authorities_set.clone();
-		let scheduled_change =
+		let scheduled_change = GrandpaConsensusLogReader::<BlockNumberOf<C>>::find_scheduled_change(
-			GrandpaConsensusLogReader::<BlockNumberOf<C>>::find_authorities_change(
+			initial_header.digest(),
-				initial_header.digest(),
+		);
-			);
 		assert!(
 			scheduled_change.as_ref().map(|c| c.delay.is_zero()).unwrap_or(true),
 			"GRANDPA authorities change at {} scheduled to happen in {:?} blocks. We expect\