Fix solo to para custom header return (#882)

* Adds an integration test for testing the migration

* Fix the custom validation header use case

cumulus/client/collator/src/lib.rs

@@ -18,11 +18,12 @@
 
 use cumulus_client_network::WaitToAnnounce;
 use cumulus_primitives_core::{
-	relay_chain::Hash as PHash, CollectCollationInfo, ParachainBlockData, PersistedValidationData,
+	relay_chain::Hash as PHash, CollationInfo, CollectCollationInfo, ParachainBlockData,
+	PersistedValidationData,
 };
 
 use sc_client_api::BlockBackend;
-use sp_api::ProvideRuntimeApi;
+use sp_api::{ApiExt, ProvideRuntimeApi};
 use sp_consensus::BlockStatus;
 use sp_core::traits::SpawnNamed;
 use sp_runtime::{
@@ -36,7 +37,7 @@ use polkadot_node_primitives::{
 };
 use polkadot_node_subsystem::messages::{CollationGenerationMessage, CollatorProtocolMessage};
 use polkadot_overseer::Handle as OverseerHandle;
-use polkadot_primitives::v1::{CollatorPair, HeadData, Id as ParaId};
+use polkadot_primitives::v1::{CollatorPair, Id as ParaId};
 
 use codec::{Decode, Encode};
 use futures::{channel::oneshot, FutureExt};
@@ -144,30 +145,59 @@ where
 		}
 	}
 
+	/// Fetch the collation info from the runtime.
+	///
+	/// Returns `Ok(Some(_))` on success, `Err(_)` on error or `Ok(None)` if the runtime api isn't implemented by the runtime.
+	fn fetch_collation_info(
+		&self,
+		block_hash: Block::Hash,
+		header: &Block::Header,
+	) -> Result<Option<CollationInfo>, sp_api::ApiError> {
+		let runtime_api = self.runtime_api.runtime_api();
+		let block_id = BlockId::Hash(block_hash);
+
+		let api_version =
+			match runtime_api.api_version::<dyn CollectCollationInfo<Block>>(&block_id)? {
+				Some(version) => version,
+				None => {
+					tracing::error!(
+						target: LOG_TARGET,
+						"Could not fetch `CollectCollationInfo` runtime api version."
+					);
+					return Ok(None)
+				},
+			};
+
+		let collation_info = if api_version < 2 {
+			#[allow(deprecated)]
+			runtime_api
+				.collect_collation_info_before_version_2(&block_id)?
+				.into_latest(header.encode().into())
+		} else {
+			runtime_api.collect_collation_info(&block_id, header)?
+		};
+
+		Ok(Some(collation_info))
+	}
+
 	fn build_collation(
-		&mut self,
+		&self,
 		block: ParachainBlockData<Block>,
 		block_hash: Block::Hash,
 	) -> Option<Collation> {
 		let block_data = BlockData(block.encode());
-		let header = block.into_header();
-		let head_data = HeadData(header.encode());
 
-		let collation_info = match self
-			.runtime_api
-			.runtime_api()
-			.collect_collation_info(&BlockId::Hash(block_hash))
-		{
-			Ok(ci) => ci,
-			Err(e) => {
+		let collation_info = self
+			.fetch_collation_info(block_hash, block.header())
+			.map_err(|e| {
 				tracing::error!(
 					target: LOG_TARGET,
 					error = ?e,
 					"Failed to collect collation info.",
-				);
-				return None
-			},
-		};
+				)
+			})
+			.ok()
+			.flatten()?;
 
 		Some(Collation {
 			upward_messages: collation_info.upward_messages,
@@ -175,7 +205,7 @@ where
 			processed_downward_messages: collation_info.processed_downward_messages,
 			horizontal_messages: collation_info.horizontal_messages,
 			hrmp_watermark: collation_info.hrmp_watermark,
-			head_data,
+			head_data: collation_info.head_data,
 			proof_of_validity: PoV { block_data },
 		})
 	}

cumulus/pallets/parachain-system/src/lib.rs

@@ -27,6 +27,7 @@
 //!
 //! Users must ensure that they register this pallet as an inherent provider.
 
+use codec::Encode;
 use cumulus_primitives_core::{
 	relay_chain, AbridgedHostConfiguration, ChannelStatus, CollationInfo, DmpMessageHandler,
 	GetChannelInfo, InboundDownwardMessage, InboundHrmpMessage, MessageSendError, OnValidationData,
@@ -908,15 +909,22 @@ impl<T: Config> Pallet<T> {
 
 	/// Returns the [`CollationInfo`] of the current active block.
 	///
+	/// The given `header` is the header of the built block we are collecting the collation info for.
+	///
 	/// This is expected to be used by the
 	/// [`CollectCollationInfo`](cumulus_primitives_core::CollectCollationInfo) runtime api.
-	pub fn collect_collation_info() -> CollationInfo {
+	pub fn collect_collation_info(header: &T::Header) -> CollationInfo {
 		CollationInfo {
 			hrmp_watermark: HrmpWatermark::<T>::get(),
 			horizontal_messages: HrmpOutboundMessages::<T>::get(),
 			upward_messages: UpwardMessages::<T>::get(),
 			processed_downward_messages: ProcessedDownwardMessages::<T>::get(),
 			new_validation_code: NewValidationCode::<T>::get().map(Into::into),
+			// Check if there is a custom header that will also be returned by the validation phase.
+			// If so, we need to also return it here.
+			head_data: CustomValidationHeadData::<T>::get()
+				.map_or_else(|| header.encode(), |v| v)
+				.into(),
 		}
 	}
 

cumulus/parachain-template/runtime/src/lib.rs

@@ -731,8 +731,8 @@ impl_runtime_apis! {
 	}
 
 	impl cumulus_primitives_core::CollectCollationInfo<Block> for Runtime {
-		fn collect_collation_info() -> cumulus_primitives_core::CollationInfo {
-			ParachainSystem::collect_collation_info()
+		fn collect_collation_info(header: &<Block as BlockT>::Header) -> cumulus_primitives_core::CollationInfo {
+			ParachainSystem::collect_collation_info(header)
 		}
 	}
 

cumulus/polkadot-parachains/rococo-parachain/src/lib.rs

@@ -697,8 +697,8 @@ impl_runtime_apis! {
 	}
 
 	impl cumulus_primitives_core::CollectCollationInfo<Block> for Runtime {
-		fn collect_collation_info() -> cumulus_primitives_core::CollationInfo {
-			ParachainSystem::collect_collation_info()
+		fn collect_collation_info(header: &<Block as BlockT>::Header) -> cumulus_primitives_core::CollationInfo {
+			ParachainSystem::collect_collation_info(header)
 		}
 	}
 }

cumulus/polkadot-parachains/seedling/src/lib.rs

@@ -303,8 +303,8 @@ impl_runtime_apis! {
 	}
 
 	impl cumulus_primitives_core::CollectCollationInfo<Block> for Runtime {
-		fn collect_collation_info() -> cumulus_primitives_core::CollationInfo {
-			ParachainSystem::collect_collation_info()
+		fn collect_collation_info(header: &<Block as BlockT>::Header) -> cumulus_primitives_core::CollationInfo {
+			ParachainSystem::collect_collation_info(header)
 		}
 	}
 }

cumulus/polkadot-parachains/shell/src/lib.rs

@@ -381,8 +381,8 @@ impl_runtime_apis! {
 	}
 
 	impl cumulus_primitives_core::CollectCollationInfo<Block> for Runtime {
-		fn collect_collation_info() -> cumulus_primitives_core::CollationInfo {
-			ParachainSystem::collect_collation_info()
+		fn collect_collation_info(header: &<Block as BlockT>::Header) -> cumulus_primitives_core::CollationInfo {
+			ParachainSystem::collect_collation_info(header)
 		}
 	}
 }

cumulus/polkadot-parachains/statemine/src/lib.rs

@@ -892,8 +892,8 @@ impl_runtime_apis! {
 	}
 
 	impl cumulus_primitives_core::CollectCollationInfo<Block> for Runtime {
-		fn collect_collation_info() -> cumulus_primitives_core::CollationInfo {
-			ParachainSystem::collect_collation_info()
+		fn collect_collation_info(header: &<Block as BlockT>::Header) -> cumulus_primitives_core::CollationInfo {
+			ParachainSystem::collect_collation_info(header)
 		}
 	}
 

cumulus/polkadot-parachains/statemint/src/lib.rs

@@ -893,8 +893,8 @@ impl_runtime_apis! {
 	}
 
 	impl cumulus_primitives_core::CollectCollationInfo<Block> for Runtime {
-		fn collect_collation_info() -> cumulus_primitives_core::CollationInfo {
-			ParachainSystem::collect_collation_info()
+		fn collect_collation_info(header: &<Block as BlockT>::Header) -> cumulus_primitives_core::CollationInfo {
+			ParachainSystem::collect_collation_info(header)
 		}
 	}
 

cumulus/polkadot-parachains/westmint/src/lib.rs

@@ -890,8 +890,8 @@ impl_runtime_apis! {
 	}
 
 	impl cumulus_primitives_core::CollectCollationInfo<Block> for Runtime {
-		fn collect_collation_info() -> cumulus_primitives_core::CollationInfo {
-			ParachainSystem::collect_collation_info()
+		fn collect_collation_info(header: &<Block as BlockT>::Header) -> cumulus_primitives_core::CollationInfo {
+			ParachainSystem::collect_collation_info(header)
 		}
 	}
 

cumulus/primitives/core/src/lib.rs

@@ -19,6 +19,7 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use codec::{Decode, Encode};
+use polkadot_parachain::primitives::HeadData;
 use sp_runtime::{traits::Block as BlockT, RuntimeDebug};
 use sp_std::prelude::*;
 
@@ -200,8 +201,10 @@ impl<B: BlockT> ParachainBlockData<B> {
 }
 
 /// Information about a collation.
+///
+/// This was used in version 1 of the [`CollectCollationInfo`] runtime api.
 #[derive(Clone, Debug, codec::Decode, codec::Encode, PartialEq)]
-pub struct CollationInfo {
+pub struct CollationInfoV1 {
 	/// Messages destined to be interpreted by the Relay chain itself.
 	pub upward_messages: Vec<UpwardMessage>,
 	/// The horizontal messages sent by the parachain.
@@ -214,10 +217,48 @@ pub struct CollationInfo {
 	pub hrmp_watermark: relay_chain::v1::BlockNumber,
 }
 
-sp_api::decl_runtime_apis! {
-	/// Runtime api to collect information about a collation.
-	pub trait CollectCollationInfo {
-		/// Collect information about a collation.
-		fn collect_collation_info() -> CollationInfo;
+impl CollationInfoV1 {
+	/// Convert into the latest version of the [`CollationInfo`] struct.
+	pub fn into_latest(self, head_data: HeadData) -> CollationInfo {
+		CollationInfo {
+			upward_messages: self.upward_messages,
+			horizontal_messages: self.horizontal_messages,
+			new_validation_code: self.new_validation_code,
+			processed_downward_messages: self.processed_downward_messages,
+			hrmp_watermark: self.hrmp_watermark,
+			head_data,
+		}
+	}
+}
+
+/// Information about a collation.
+#[derive(Clone, Debug, codec::Decode, codec::Encode, PartialEq)]
+pub struct CollationInfo {
+	/// Messages destined to be interpreted by the Relay chain itself.
+	pub upward_messages: Vec<UpwardMessage>,
+	/// The horizontal messages sent by the parachain.
+	pub horizontal_messages: Vec<OutboundHrmpMessage>,
+	/// New validation code.
+	pub new_validation_code: Option<relay_chain::v1::ValidationCode>,
+	/// The number of messages processed from the DMQ.
+	pub processed_downward_messages: u32,
+	/// The mark which specifies the block number up to which all inbound HRMP messages are processed.
+	pub hrmp_watermark: relay_chain::v1::BlockNumber,
+	/// The head data, aka encoded header, of the block that corresponds to the collation.
+	pub head_data: HeadData,
+}
+
+sp_api::decl_runtime_apis! {
+	/// Runtime api to collect information about a collation.
+	#[api_version(2)]
+	pub trait CollectCollationInfo {
+		/// Collect information about a collation.
+		#[changed_in(2)]
+		fn collect_collation_info() -> CollationInfoV1;
+		/// Collect information about a collation.
+		///
+		/// The given `header` is the header of the built block for that
+		/// we are collecting the collation info for.
+		fn collect_collation_info(header: &Block::Header) -> CollationInfo;
 	}
 }

cumulus/test/runtime/src/lib.rs

@@ -440,8 +440,8 @@ impl_runtime_apis! {
 	}
 
 	impl cumulus_primitives_core::CollectCollationInfo<Block> for Runtime {
-		fn collect_collation_info() -> cumulus_primitives_core::CollationInfo {
-			ParachainSystem::collect_collation_info()
+		fn collect_collation_info(header: &<Block as BlockT>::Header) -> cumulus_primitives_core::CollationInfo {
+			ParachainSystem::collect_collation_info(header)
 		}
 	}
 }

cumulus/test/service/tests/full_node_catching_up.rs

@@ -19,7 +19,7 @@ use cumulus_test_service::{initial_head_data, run_relay_chain_validator_node, Ke
 
 #[substrate_test_utils::test]
 #[ignore]
-async fn test_collating_and_non_collator_mode_catching_up() {
+async fn test_full_node_catching_up() {
 	let mut builder = sc_cli::LoggerBuilder::new("");
 	builder.with_colors(false);
 	let _ = builder.init();

cumulus/test/service/tests/migrate_solo_to_para.rs

@@ -0,0 +1,111 @@
+// Copyright 2020-2021 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Test migration from parachain A to parachain B by returning the header of parachain B.
+//!
+//! This can be seen as a test of the fundamentals of the solo to parachain migration use case.
+//! The prerequisite is to have a running solo chain and a running parachain. The idea is that
+//! the solo chain is being stopped at a given point and sends its last header to the running parachain.
+//! The parachain will return this header as part of the validation phase on the relay chain to enact
+//! this header as its current latest state. As the old running parachain doesn't know this header, it will
+//! stop to produce new blocks. However, the old solo chain can now produce blocks using the parachain slot.
+//! (Be aware, that this is just a highlevel description and some parts are omitted.)
+
+use codec::Encode;
+use cumulus_primitives_core::ParaId;
+use cumulus_test_service::{initial_head_data, run_relay_chain_validator_node, Keyring::*};
+use sc_client_api::{BlockBackend, UsageProvider};
+use sp_runtime::generic::BlockId;
+
+#[substrate_test_utils::test]
+#[ignore]
+async fn test_migrate_solo_to_para() {
+	let mut builder = sc_cli::LoggerBuilder::new("");
+	builder.with_colors(false);
+	let _ = builder.init();
+
+	let para_id = ParaId::from(100);
+
+	let tokio_handle = tokio::runtime::Handle::current();
+
+	// start alice
+	let alice = run_relay_chain_validator_node(tokio_handle.clone(), Alice, || {}, Vec::new());
+
+	// start bob
+	let bob =
+		run_relay_chain_validator_node(tokio_handle.clone(), Bob, || {}, vec![alice.addr.clone()]);
+
+	// register parachain
+	alice
+		.register_parachain(
+			para_id,
+			cumulus_test_runtime::WASM_BINARY
+				.expect("You need to build the WASM binary to run this test!")
+				.to_vec(),
+			initial_head_data(para_id),
+		)
+		.await
+		.unwrap();
+
+	// run the parachain that will be used to return the header of the solo chain.
+	let parachain =
+		cumulus_test_service::TestNodeBuilder::new(para_id, tokio_handle.clone(), Charlie)
+			.enable_collator()
+			.connect_to_relay_chain_nodes(vec![&alice, &bob])
+			.build()
+			.await;
+
+	// run the solo chain (in our case this is also already a parachain, but as it has a different genesis it will not produce any blocks.)
+	let solo = cumulus_test_service::TestNodeBuilder::new(para_id, tokio_handle, Dave)
+		.enable_collator()
+		.connect_to_relay_chain_nodes(vec![&alice, &bob])
+		// Set some random value in the genesis state to create a different genesis hash.
+		.update_storage_parachain(|| {
+			sp_io::storage::set(b"test", b"test");
+		})
+		.build()
+		.await;
+
+	parachain.wait_for_blocks(2).await;
+
+	// Ensure that both chains have a different genesis hash.
+	assert_ne!(
+		parachain.client.block_hash(0).ok().flatten().unwrap(),
+		solo.client.block_hash(0).ok().flatten().unwrap(),
+	);
+
+	let solo_chain_header = solo.client.header(&BlockId::Number(0)).ok().flatten().unwrap();
+
+	// Send the transaction to set the custom header, aka the header of the solo chain.
+	parachain
+		.send_extrinsic(
+			cumulus_test_runtime::TestPalletCall::set_custom_validation_head_data {
+				custom_header: solo_chain_header.encode(),
+			},
+			Alice,
+		)
+		.await
+		.unwrap();
+
+	// Wait until the solo chain produced a block now as a parachain.
+	solo.wait_for_blocks(1).await;
+
+	let parachain_best = parachain.client.usage_info().chain.best_number;
+
+	// Wait for some more blocks and check that the old parachain doesn't produced/imported any new blocks.
+	solo.wait_for_blocks(2).await;
+	assert_eq!(parachain_best, parachain.client.usage_info().chain.best_number);
+}