approval-voting: populate session cache in advance (#3954)

* try populating session cache in advance

* remove unused arg

* fmt

* fix compilation

* fix tests

* Revert "fix tests"

This reverts commit e8222b1108e09a39727a38e3b4e4c3061642a213.

* fix tests

* bump dispute window const by 1

* fix tests

polkadot/node/core/approval-voting/src/import.rs

@@ -324,7 +324,7 @@ pub(crate) async fn handle_new_head(
 		}
 	};
 
-	match state.session_window.cache_session_info_for_head(ctx, head, &header).await {
+	match state.session_window.cache_session_info_for_head(ctx, head).await {
 		Err(e) => {
 			tracing::debug!(
 				target: LOG_TARGET,
@@ -1236,7 +1236,7 @@ pub(crate) mod tests {
 					h,
 					RuntimeApiRequest::SessionIndexForChild(c_tx),
 				)) => {
-					assert_eq!(h, parent_hash.clone());
+					assert_eq!(h, hash);
 					let _ = c_tx.send(Ok(session));
 				}
 			);

polkadot/node/core/approval-voting/src/tests.rs

@@ -786,8 +786,8 @@ async fn import_block(
 				RuntimeApiRequest::SessionIndexForChild(s_tx)
 			)
 		) => {
-			let hash = &hashes[number.saturating_sub(1) as usize];
-			assert_eq!(req_block_hash, hash.0.clone());
+			let hash = &hashes[number as usize];
+			assert_eq!(req_block_hash, hash.0);
 			s_tx.send(Ok(number.into())).unwrap();
 		}
 	);

polkadot/node/core/dispute-coordinator/src/real/mod.rs

@@ -478,22 +478,7 @@ async fn handle_new_activations(
 	new_activations: impl IntoIterator<Item = Hash>,
 ) -> Result<(), Error> {
 	for new_leaf in new_activations {
-		let block_header = {
-			let (tx, rx) = oneshot::channel();
-
-			ctx.send_message(ChainApiMessage::BlockHeader(new_leaf, tx)).await;
-
-			match rx.await?? {
-				None => continue,
-				Some(header) => header,
-			}
-		};
-
-		match state
-			.rolling_session_window
-			.cache_session_info_for_head(ctx, new_leaf, &block_header)
-			.await
-		{
+		match state.rolling_session_window.cache_session_info_for_head(ctx, new_leaf).await {
 			Err(e) => {
 				tracing::warn!(
 					target: LOG_TARGET,