Clean obsolete BABE's weight data (#10748)

* Clean obsolete BABE weight data
* Take out test assertion from check closure
* Optimize metadata access using `HeaderMetadata` trait
* Apply suggestions from code review
* Introduce finalize and import pre-commit synchronous actions
* Do not hold locks between internal methods calls
* Remove unused generic bound
* Apply suggestions from code review
* Register BABE's pre-commit actions on `block_import` instead of `start_babe`
* PreCommit actions should be `Fn` instead of `FnMut`
* More robust safenet in case of malformed finality notifications

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>

substrate/client/api/src/backend.rs

@@ -75,6 +75,8 @@ pub struct ImportSummary<Block: BlockT> {
 /// Contains information about the block that just got finalized,
 /// including tree heads that became stale at the moment of finalization.
 pub struct FinalizeSummary<Block: BlockT> {
+	/// Last finalized block header.
+	pub header: Block::Header,
 	/// Blocks that were finalized.
 	/// The last entry is the one that has been explicitly finalized.
 	pub finalized: Vec<Block::Hash>,

substrate/client/api/src/client.rs

@@ -27,7 +27,8 @@ use sp_runtime::{
 };
 use std::{collections::HashSet, convert::TryFrom, fmt, sync::Arc};
 
-use crate::{blockchain::Info, notifications::StorageEventStream};
+use crate::{blockchain::Info, notifications::StorageEventStream, FinalizeSummary, ImportSummary};
+
 use sc_transaction_pool_api::ChainEvent;
 use sc_utils::mpsc::TracingUnboundedReceiver;
 use sp_blockchain;
@@ -76,6 +77,34 @@ pub trait BlockchainEvents<Block: BlockT> {
 	) -> sp_blockchain::Result<StorageEventStream<Block::Hash>>;
 }
 
+/// List of operations to be performed on storage aux data.
+/// First tuple element is the encoded data key.
+/// Second tuple element is the encoded optional data to write.
+/// If `None`, the key and the associated data are deleted from storage.
+pub type AuxDataOperations = Vec<(Vec<u8>, Option<Vec<u8>>)>;
+
+/// Callback invoked before committing the operations created during block import.
+/// This gives the opportunity to perform auxiliary pre-commit actions and optionally
+/// enqueue further storage write operations to be atomically performed on commit.
+pub type OnImportAction<Block> =
+	Box<dyn (Fn(&BlockImportNotification<Block>) -> AuxDataOperations) + Send>;
+
+/// Callback invoked before committing the operations created during block finalization.
+/// This gives the opportunity to perform auxiliary pre-commit actions and optionally
+/// enqueue further storage write operations to be atomically performed on commit.
+pub type OnFinalityAction<Block> =
+	Box<dyn (Fn(&FinalityNotification<Block>) -> AuxDataOperations) + Send>;
+
+/// Interface to perform auxiliary actions before committing a block import or
+/// finality operation.
+pub trait PreCommitActions<Block: BlockT> {
+	/// Actions to be performed on block import.
+	fn register_import_action(&self, op: OnImportAction<Block>);
+
+	/// Actions to be performed on block finalization.
+	fn register_finality_action(&self, op: OnFinalityAction<Block>);
+}
+
 /// Interface for fetching block data.
 pub trait BlockBackend<Block: BlockT> {
 	/// Get block body by ID. Returns `None` if the body is not stored.
@@ -300,3 +329,27 @@ impl<B: BlockT> From<FinalityNotification<B>> for ChainEvent<B> {
 		Self::Finalized { hash: n.hash, tree_route: n.tree_route }
 	}
 }
+
+impl<B: BlockT> From<FinalizeSummary<B>> for FinalityNotification<B> {
+	fn from(mut summary: FinalizeSummary<B>) -> Self {
+		let hash = summary.finalized.pop().unwrap_or_default();
+		FinalityNotification {
+			hash,
+			header: summary.header,
+			tree_route: Arc::new(summary.finalized),
+			stale_heads: Arc::new(summary.stale_heads),
+		}
+	}
+}
+
+impl<B: BlockT> From<ImportSummary<B>> for BlockImportNotification<B> {
+	fn from(summary: ImportSummary<B>) -> Self {
+		BlockImportNotification {
+			hash: summary.hash,
+			origin: summary.origin,
+			header: summary.header,
+			is_new_best: summary.is_new_best,
+			tree_route: summary.tree_route.map(Arc::new),
+		}
+	}
+}