address review: use enum for parent head-data

polkadot/node/core/prospective-parachains/src/lib.rs

@@ -36,8 +36,9 @@ use futures::{channel::oneshot, prelude::*};
 use polkadot_node_subsystem::{
 	messages::{
 		ChainApiMessage, FragmentTreeMembership, HypotheticalCandidate,
-		HypotheticalFrontierRequest, IntroduceCandidateRequest, ProspectiveParachainsMessage,
-		ProspectiveValidationDataRequest, RuntimeApiMessage, RuntimeApiRequest,
+		HypotheticalFrontierRequest, IntroduceCandidateRequest, ParentHeadData,
+		ProspectiveParachainsMessage, ProspectiveValidationDataRequest, RuntimeApiMessage,
+		RuntimeApiRequest,
 	},
 	overseer, ActiveLeavesUpdate, FromOrchestra, OverseerSignal, SpawnedSubsystem, SubsystemError,
 };
@@ -771,9 +772,14 @@ fn answer_prospective_validation_data_request(
 		Some(s) => s,
 	};
 
-	let mut head_data = request
-		.maybe_parent_head_data
-		.or_else(|| storage.head_data_by_hash(&request.parent_head_data_hash).map(|x| x.clone()));
+	let (mut head_data, parent_head_data_hash) = match request.parent_head_data {
+		ParentHeadData::OnlyHash(parent_head_data_hash) => (
+			storage.head_data_by_hash(&parent_head_data_hash).map(|x| x.clone()),
+			parent_head_data_hash,
+		),
+		ParentHeadData::WithData { head_data, hash } => (Some(head_data), hash),
+	};
+
 	let mut relay_parent_info = None;
 	let mut max_pov_size = None;
 
@@ -791,7 +797,7 @@ fn answer_prospective_validation_data_request(
 		}
 		if head_data.is_none() {
 			let required_parent = &fragment_tree.scope().base_constraints().required_parent;
-			if required_parent.hash() == request.parent_head_data_hash {
+			if required_parent.hash() == parent_head_data_hash {
 				head_data = Some(required_parent.clone());
 			}
 		}

polkadot/node/core/prospective-parachains/src/tests.rs

@@ -19,7 +19,7 @@ use assert_matches::assert_matches;
 use polkadot_node_subsystem::{
 	errors::RuntimeApiError,
 	messages::{
-		AllMessages, HypotheticalFrontierRequest, ProspectiveParachainsMessage,
+		AllMessages, HypotheticalFrontierRequest, ParentHeadData, ProspectiveParachainsMessage,
 		ProspectiveValidationDataRequest,
 	},
 };
@@ -472,8 +472,7 @@ async fn get_pvd(
 	let request = ProspectiveValidationDataRequest {
 		para_id,
 		candidate_relay_parent,
-		parent_head_data_hash: parent_head_data.hash(),
-		maybe_parent_head_data: None,
+		parent_head_data: ParentHeadData::OnlyHash(parent_head_data.hash()),
 	};
 	let (tx, rx) = oneshot::channel();
 	virtual_overseer

polkadot/node/network/collator-protocol/src/validator_side/mod.rs

@@ -44,7 +44,7 @@ use polkadot_node_subsystem::{
 	jaeger,
 	messages::{
 		CanSecondRequest, CandidateBackingMessage, CollatorProtocolMessage, IfDisconnected,
-		NetworkBridgeEvent, NetworkBridgeTxMessage, ProspectiveParachainsMessage,
+		NetworkBridgeEvent, NetworkBridgeTxMessage, ParentHeadData, ProspectiveParachainsMessage,
 		ProspectiveValidationDataRequest,
 	},
 	overseer, CollatorProtocolSenderTrait, FromOrchestra, OverseerSignal, PerLeafSpan,
@@ -1784,13 +1784,15 @@ where
 {
 	let (tx, rx) = oneshot::channel();
 
-	let request = ProspectiveValidationDataRequest {
-		para_id,
-		candidate_relay_parent,
-		parent_head_data_hash,
-		maybe_parent_head_data,
+	let parent_head_data = if let Some(head_data) = maybe_parent_head_data {
+		ParentHeadData::WithData { head_data, hash: parent_head_data_hash }
+	} else {
+		ParentHeadData::OnlyHash(parent_head_data_hash)
 	};
 
+	let request =
+		ProspectiveValidationDataRequest { para_id, candidate_relay_parent, parent_head_data };
+
 	sender
 		.send_message(ProspectiveParachainsMessage::GetProspectiveValidationData(request, tx))
 		.await;

polkadot/node/subsystem-types/src/messages.rs

@@ -1108,11 +1108,22 @@ pub struct ProspectiveValidationDataRequest {
 	pub para_id: ParaId,
 	/// The relay-parent of the candidate.
 	pub candidate_relay_parent: Hash,
-	/// The parent head-data hash.
-	pub parent_head_data_hash: Hash,
-	/// Optionally, the head-data of the parent.
-	/// This will be provided for collations with elastic scaling enabled.
-	pub maybe_parent_head_data: Option<HeadData>,
+	/// The parent head-data.
+	pub parent_head_data: ParentHeadData,
+}
+
+/// The parent head-data hash with optional data itself.
+#[derive(Debug)]
+pub enum ParentHeadData {
+	/// Parent head-data hash.
+	OnlyHash(Hash),
+	/// Parent head-data along with its hash.
+	WithData {
+		/// This will be provided for collations with elastic scaling enabled.
+		head_data: HeadData,
+		/// Parent head-data hash.
+		hash: Hash,
+	},
 }
 
 /// Indicates the relay-parents whose fragment tree a candidate