test-utils/fix: Parachains test-utils relay parent descendants mock data

cumulus/parachains/runtimes/assets/asset-hub-westend/src/lib.rs

@@ -133,6 +133,22 @@ use xcm::latest::prelude::{
 	NetworkId, NonFungible, ParentThen, Response, WeightLimit, XCM_VERSION,
 };
 
+/// Build with an offset of 1 behind the relay chain.
+const RELAY_PARENT_OFFSET: u32 = 1;
+
+/// The upper limit of how many parachain blocks are processed by the relay chain per
+/// parent. Limits the number of blocks authored per slot. This determines the minimum
+/// block time of the parachain:
+/// `RELAY_CHAIN_SLOT_DURATION_MILLIS/BLOCK_PROCESSING_VELOCITY`
+const BLOCK_PROCESSING_VELOCITY: u32 = 3;
+
+/// Maximum number of blocks simultaneously accepted by the Runtime, not yet included
+/// into the relay chain.
+const UNINCLUDED_SEGMENT_CAPACITY: u32 = (2 + RELAY_PARENT_OFFSET) * BLOCK_PROCESSING_VELOCITY + 1;
+
+/// Relay chain slot duration, in milliseconds.
+const RELAY_CHAIN_SLOT_DURATION_MILLIS: u32 = 6000;
+
 impl_opaque_keys! {
 	pub struct SessionKeys {
 		pub aura: Aura,
@@ -902,7 +918,7 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type ReservedXcmpWeight = ReservedXcmpWeight;
 	type CheckAssociatedRelayNumber = RelayNumberMonotonicallyIncreases;
 	type ConsensusHook = ConsensusHook;
-	type RelayParentOffset = ConstU32<0>;
+	type RelayParentOffset = ConstU32<RELAY_PARENT_OFFSET>;
 }
 
 type ConsensusHook = cumulus_pallet_aura_ext::FixedVelocityConsensusHook<
@@ -1746,7 +1762,7 @@ pallet_revive::impl_runtime_apis_plus_revive_traits!(
 
 	impl cumulus_primitives_core::RelayParentOffsetApi<Block> for Runtime {
 		fn relay_parent_offset() -> u32 {
-			0
+			RELAY_PARENT_OFFSET
 		}
 	}
 

cumulus/parachains/runtimes/test-utils/src/lib.rs

@@ -331,14 +331,22 @@ where
 			AllPalletsWithoutSystem::on_initialize(next_block_number);
 
 			let parent_head = HeadData(header.encode());
+
+			// Get RelayParentOffset from the parachain system pallet config.
+			let num_descendants = 1 +
+				<Runtime as cumulus_pallet_parachain_system::Config>::RelayParentOffset::get()
+					.saturated_into::<u64>();
+
 			let sproof_builder = RelayStateSproofBuilder {
 				para_id: <Runtime>::SelfParaId::get(),
 				included_para_head: parent_head.clone().into(),
+				num_authorities: num_descendants,
 				..Default::default()
 			};
 
-			let (relay_parent_storage_root, relay_chain_state) =
-				sproof_builder.into_state_root_and_proof();
+			let (relay_parent_storage_root, relay_chain_state, relay_parent_descendants) =
+				sproof_builder.into_state_root_proof_and_descendants(num_descendants);
+
 			let inherent_data = ParachainInherentData {
 				validation_data: PersistedValidationData {
 					parent_head,
@@ -349,7 +357,7 @@ where
 				relay_chain_state,
 				downward_messages: Default::default(),
 				horizontal_messages: Default::default(),
-				relay_parent_descendants: Default::default(),
+				relay_parent_descendants,
 				collator_peer_id: None,
 			};
 
@@ -689,12 +697,16 @@ pub fn mock_open_hrmp_channel<
 	let timestamp = slot.saturating_mul(slot_durations.para.as_millis());
 	let relay_slot = Slot::from_timestamp(timestamp.into(), slot_durations.relay);
 
+	// Get RelayParentOffset from the parachain system pallet config.
+	let num_descendants = 1 + C::RelayParentOffset::get().saturated_into::<u64>();
+
 	let n = 1_u32;
 	let mut sproof_builder = RelayStateSproofBuilder {
 		para_id: sender,
 		included_para_head: Some(HeadData(included_head.encode())),
 		hrmp_egress_channel_index: Some(vec![recipient]),
 		current_slot: relay_slot,
+		num_authorities: num_descendants,
 		..Default::default()
 	};
 	sproof_builder.hrmp_channels.insert(
@@ -709,7 +721,9 @@ pub fn mock_open_hrmp_channel<
 		},
 	);
 
-	let (relay_parent_storage_root, relay_chain_state) = sproof_builder.into_state_root_and_proof();
+	let (relay_parent_storage_root, relay_chain_state, relay_parent_descendants) =
+		sproof_builder.into_state_root_proof_and_descendants(num_descendants);
+
 	let vfp = PersistedValidationData {
 		relay_parent_number: n as RelayChainBlockNumber,
 		relay_parent_storage_root,
@@ -724,7 +738,7 @@ pub fn mock_open_hrmp_channel<
 			relay_chain_state,
 			downward_messages: Default::default(),
 			horizontal_messages: Default::default(),
-			relay_parent_descendants: Default::default(),
+			relay_parent_descendants,
 			collator_peer_id: None,
 		};
 		inherent_data

cumulus/test/relay-sproof-builder/Cargo.toml

@@ -15,6 +15,8 @@ workspace = true
 codec = { features = ["derive"], workspace = true }
 
 # Substrate
+sp-consensus-babe = { workspace = true }
+sp-core = { workspace = true }
 sp-runtime = { workspace = true }
 sp-state-machine = { workspace = true }
 sp-trie = { workspace = true }
@@ -31,6 +33,8 @@ std = [
 	"codec/std",
 	"cumulus-primitives-core/std",
 	"polkadot-primitives/std",
+	"sp-consensus-babe/std",
+	"sp-core/std",
 	"sp-runtime/std",
 	"sp-state-machine/std",
 	"sp-trie/std",

cumulus/test/relay-sproof-builder/src/lib.rs

@@ -17,11 +17,23 @@
 extern crate alloc;
 
 use alloc::collections::btree_map::BTreeMap;
+use codec::{Decode, Encode};
 use cumulus_primitives_core::{
 	relay_chain, AbridgedHostConfiguration, AbridgedHrmpChannel, ParaId,
 };
 use polkadot_primitives::UpgradeGoAhead;
-use sp_runtime::traits::HashingFor;
+use sp_consensus_babe::{
+	digests::{CompatibleDigestItem, PreDigest, PrimaryPreDigest},
+	AuthorityId, AuthorityPair, BabeAuthorityWeight,
+};
+use sp_core::{
+	sr25519::vrf::{VrfPreOutput, VrfProof, VrfSignature},
+	Pair, H256,
+};
+use sp_runtime::{
+	traits::{HashingFor, Header},
+	Digest, DigestItem,
+};
 use sp_trie::PrefixedMemoryDB;
 
 /// Builds a sproof (portmanteau of 'spoof' and 'proof') of the relay chain state.
@@ -49,6 +61,7 @@ pub struct RelayStateSproofBuilder {
 	pub randomness: relay_chain::Hash,
 	pub additional_key_values: Vec<(Vec<u8>, Vec<u8>)>,
 	pub included_para_head: Option<relay_chain::HeadData>,
+	pub num_authorities: u64,
 }
 
 impl Default for RelayStateSproofBuilder {
@@ -81,6 +94,7 @@ impl Default for RelayStateSproofBuilder {
 			randomness: relay_chain::Hash::default(),
 			additional_key_values: vec![],
 			included_para_head: None,
+			num_authorities: 0,
 		}
 	}
 }
@@ -129,9 +143,39 @@ impl RelayStateSproofBuilder {
 		})
 	}
 
-	pub fn into_state_root_and_proof(
+	/// Build sproof and generate relay parent descendants with the configured authorities.
+	///
+	/// Returns a tuple of (state_root, storage_proof, relay_parent_descendants).
+	pub fn into_state_root_proof_and_descendants(
 		self,
+		num_descendants: u64,
+	) -> (polkadot_primitives::Hash, sp_state_machine::StorageProof, Vec<TestHeader>) {
+		let authorities = generate_authority_pairs(self.num_authorities);
+		let (state_root, proof) = self.into_state_root_and_proof();
+		let descendants =
+			build_relay_parent_descendants(num_descendants, state_root.into(), authorities);
+		(state_root, proof, descendants)
+	}
+
+	pub fn into_state_root_and_proof(
+		mut self,
 	) -> (polkadot_primitives::Hash, sp_state_machine::StorageProof) {
+		// Generate and add authorities if num_authorities is set
+		if self.num_authorities > 0 {
+			let authorities = generate_authority_pairs(self.num_authorities);
+			let auth_pair = convert_to_authority_weight_pair(&authorities);
+
+			// Add authorities to the sproof builder
+			self.additional_key_values.push((
+				relay_chain::well_known_keys::AUTHORITIES.to_vec(),
+				auth_pair.clone().encode(),
+			));
+			self.additional_key_values.push((
+				relay_chain::well_known_keys::NEXT_AUTHORITIES.to_vec(),
+				auth_pair.encode(),
+			));
+		}
+
 		let (db, root) =
 			PrefixedMemoryDB::<HashingFor<polkadot_primitives::Block>>::default_with_root();
 		let state_version = Default::default(); // for test using default.
@@ -213,3 +257,82 @@ impl RelayStateSproofBuilder {
 		(root, proof)
 	}
 }
+
+/// Block Header type for testing
+pub type TestHeader = sp_runtime::generic::Header<u32, sp_runtime::traits::BlakeTwo256>;
+
+/// Generate a vector of AuthorityPairs
+pub fn generate_authority_pairs(num_authorities: u64) -> Vec<AuthorityPair> {
+	(0..num_authorities).map(|i| AuthorityPair::from_seed(&[i as u8; 32])).collect()
+}
+
+/// Convert AuthorityPair to (AuthorityId, BabeAuthorityWeight)
+pub fn convert_to_authority_weight_pair(
+	authorities: &[AuthorityPair],
+) -> Vec<(AuthorityId, BabeAuthorityWeight)> {
+	authorities
+		.iter()
+		.map(|auth| (auth.public().into(), Default::default()))
+		.collect()
+}
+
+/// Add a BABE pre-digest to a generic header
+pub fn add_pre_digest<Header: sp_runtime::traits::Header>(
+	header: &mut Header,
+	authority_index: u32,
+	block_number: u64,
+) {
+	/// This method generates some vrf data, but only to make the compiler happy
+	fn generate_testing_vrf() -> VrfSignature {
+		let vrf_proof_bytes = [0u8; 64];
+		let proof: VrfProof = VrfProof::decode(&mut vrf_proof_bytes.as_slice()).unwrap();
+		let vrf_pre_out_bytes = [0u8; 32];
+		let pre_output: VrfPreOutput =
+			VrfPreOutput::decode(&mut vrf_pre_out_bytes.as_slice()).unwrap();
+		VrfSignature { pre_output, proof }
+	}
+
+	let pre_digest = PrimaryPreDigest {
+		authority_index,
+		slot: block_number.into(),
+		vrf_signature: generate_testing_vrf(),
+	};
+
+	header
+		.digest_mut()
+		.push(DigestItem::babe_pre_digest(PreDigest::Primary(pre_digest)));
+}
+
+/// Create a mock chain of relay headers as descendants of the relay parent
+pub fn build_relay_parent_descendants(
+	num_headers: u64,
+	state_root: H256,
+	authorities: Vec<AuthorityPair>,
+) -> Vec<TestHeader> {
+	let mut headers = Vec::with_capacity(num_headers as usize);
+
+	let mut previous_hash = None;
+
+	for block_number in 0..=num_headers as u32 - 1 {
+		let mut header = TestHeader {
+			number: block_number,
+			parent_hash: previous_hash.unwrap_or_default(),
+			state_root,
+			extrinsics_root: H256::default(),
+			digest: Digest::default(),
+		};
+		let authority_index = block_number % (authorities.len() as u32);
+
+		// Add pre-digest
+		add_pre_digest(&mut header, authority_index, block_number as u64);
+
+		// Sign and seal the header
+		let signature = authorities[authority_index as usize].sign(header.hash().as_bytes());
+		header.digest_mut().push(DigestItem::babe_seal(signature.into()));
+
+		previous_hash = Some(header.hash());
+		headers.push(header);
+	}
+
+	headers
+}

cumulus/xcm/xcm-emulator/src/lib.rs

@@ -68,7 +68,7 @@ pub use sp_tracing;
 // Cumulus
 pub use cumulus_pallet_parachain_system::{
 	parachain_inherent::{deconstruct_parachain_inherent_data, InboundMessagesData},
-	Call as ParachainSystemCall, Pallet as ParachainSystemPallet,
+	Call as ParachainSystemCall, Config as ParachainSystemConfig, Pallet as ParachainSystemPallet,
 };
 pub use cumulus_primitives_core::{
 	relay_chain::{BlockNumber as RelayBlockNumber, HeadData, HrmpChannelId},
@@ -205,6 +205,7 @@ pub trait Network {
 		para_id: u32,
 		relay_parent_number: u32,
 		parent_head_data: HeadData,
+		relay_parent_offset: u64,
 	) -> ParachainInherentData;
 	fn send_horizontal_messages<I: Iterator<Item = (ParaId, RelayBlockNumber, Vec<u8>)>>(
 		to_para_id: u32,
@@ -731,8 +732,11 @@ macro_rules! decl_test_parachains {
 						timestamp_set.dispatch(<Self as Chain>::RuntimeOrigin::none())
 					);
 
+					// Get RelayParentOffset from the runtime
+					let relay_parent_offset = <<<Self as $crate::Chain>::Runtime as $crate::ParachainSystemConfig>::RelayParentOffset as frame_support::traits::Get<u32>>::get();
+
 					// 2. inherent: cumulus_pallet_parachain_system::Call::set_validation_data
-						let data = N::hrmp_channel_parachain_inherent_data(para_id, relay_block_number, parent_head_data);
+						let data = N::hrmp_channel_parachain_inherent_data(para_id, relay_block_number, parent_head_data, relay_parent_offset as u64);
 						let (data, mut downward_messages, mut horizontal_messages) =
 							$crate::deconstruct_parachain_inherent_data(data);
 						let inbound_messages_data = $crate::InboundMessagesData::new(
@@ -1195,11 +1199,14 @@ macro_rules! decl_test_networks {
 					para_id: u32,
 					relay_parent_number: u32,
 					parent_head_data: $crate::HeadData,
+					relay_parent_offset: u64,
 				) -> $crate::ParachainInherentData {
 					let mut sproof = $crate::RelayStateSproofBuilder::default();
 					sproof.para_id = para_id.into();
 					sproof.current_slot = $crate::polkadot_primitives::Slot::from(relay_parent_number as u64);
 					sproof.host_config.max_upward_message_size = 1024 * 1024;
+					sproof.num_authorities = relay_parent_offset + 1;
+					let num_descendants = sproof.num_authorities;
 
 					// egress channel
 					let e_index = sproof.hrmp_egress_channel_index.get_or_insert_with(Vec::new);
@@ -1227,7 +1234,8 @@ macro_rules! decl_test_networks {
 							});
 					}
 
-					let (relay_storage_root, proof) = sproof.into_state_root_and_proof();
+					let (relay_storage_root, proof, relay_parent_descendants) =
+						sproof.into_state_root_proof_and_descendants(num_descendants);
 
 					$crate::ParachainInherentData {
 						validation_data: $crate::PersistedValidationData {
@@ -1239,7 +1247,7 @@ macro_rules! decl_test_networks {
 						relay_chain_state: proof,
 						downward_messages: Default::default(),
 						horizontal_messages: Default::default(),
-						relay_parent_descendants: Default::default(),
+						relay_parent_descendants,
 						collator_peer_id: None,
 					}
 				}

prdoc/pr_10541.prdoc

@@ -0,0 +1,24 @@
+title: 'test-utils/fix: Parachains test-utils relay parent descendants mock data'
+doc:
+- audience: Node Dev
+  description: |-
+    This PR ensures that the parachains test-utils crate has 2 relay parent descendants for testing purposes.
+
+    Effectively fixes a panic because we missed this mock data for chains that started with `RP_offset > 0`:
+
+    ```
+     Unable to verify provided relay parent descendants. expected_rp_descendants_num: 1 error: InvalidNumberOfDescendants { expected: 2, received: 0 }
+    note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+    ```
+
+    Detected in:
+    - https://github.com/polkadot-fellows/runtimes/actions/runs/19857064730/job/56897622908?pr=1018
+
+    Unblocks:
+    - https://github.com/polkadot-fellows/runtimes/pull/1018
+
+    Inspired by a similar fix I've introduced in:
+    - https://github.com/paritytech/polkadot-sdk/pull/9880
+crates:
+- name: parachains-runtimes-test-utils
+  bump: patch