From 0ff80d0355b75f09f123a2ecc5283201790ed547 Mon Sep 17 00:00:00 2001
From: Cecile Tonglet <cecile@parity.io>
Date: Tue, 26 May 2020 17:23:36 +0200
Subject: [PATCH] Add HeaderBackend trait to BuildParachainContext for cumulus
 validation (#1153)

---
 polkadot/collator/src/lib.rs   | 3 ++-
 polkadot/service/src/client.rs | 7 ++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/polkadot/collator/src/lib.rs b/polkadot/collator/src/lib.rs
index 7e4d44c0d9..6e7a803df1 100644
--- a/polkadot/collator/src/lib.rs
+++ b/polkadot/collator/src/lib.rs
@@ -53,6 +53,7 @@ use std::pin::Pin;
 use futures::{future, Future, Stream, FutureExt, TryFutureExt, StreamExt, task::Spawn};
 use log::warn;
 use sc_client_api::{StateBackend, BlockchainEvents};
+use sp_blockchain::HeaderBackend;
 use sp_core::Pair;
 use polkadot_primitives::{
 	BlockId, Hash, Block,
@@ -128,7 +129,7 @@ pub trait BuildParachainContext {
 		network: impl Network + Clone + 'static,
 	) -> Result<Self::ParachainContext, ()>
 		where
-			Client: ProvideRuntimeApi<Block> + Send + Sync + BlockchainEvents<Block> + 'static,
+			Client: ProvideRuntimeApi<Block> + HeaderBackend<Block> + BlockchainEvents<Block> + Send + Sync + 'static,
 			Client::Api: RuntimeApiCollection<Extrinsic>,
 			<Client::Api as ApiExt<Block>>::StateBackend: StateBackend<HashFor<Block>>,
 			Extrinsic: codec::Codec + Send + Sync + 'static,
diff --git a/polkadot/service/src/client.rs b/polkadot/service/src/client.rs
index f4d6fe62dc..28d2bccabb 100644
--- a/polkadot/service/src/client.rs
+++ b/polkadot/service/src/client.rs
@@ -16,16 +16,17 @@
 
 //! Polkadot Client meta trait
 
-use sc_client_api::BlockchainEvents;
 use sp_api::{ProvideRuntimeApi, ConstructRuntimeApi, CallApiAt};
+use sp_blockchain::HeaderBackend;
 use sp_runtime::traits::Block as BlockT;
-use sc_client_api::Backend as BackendT;
+use sc_client_api::{Backend as BackendT, BlockchainEvents};
 
 /// Polkadot client abstraction, this super trait only pulls in functionality required for
 /// polkadot internal crates like polkadot-collator.
 pub trait PolkadotClient<Block, Backend, Runtime>:
 	BlockchainEvents<Block> + Sized + Send + Sync
 	+ ProvideRuntimeApi<Block, Api = Runtime::RuntimeApi>
+	+ HeaderBackend<Block>
 	+ CallApiAt<
 		Block,
 		Error = sp_blockchain::Error,
@@ -42,7 +43,7 @@ impl<Block, Backend, Runtime, Client> PolkadotClient<Block, Backend, Runtime> fo
 		Block: BlockT,
 		Runtime: ConstructRuntimeApi<Block, Self>,
 		Backend: BackendT<Block>,
-		Client: BlockchainEvents<Block> + ProvideRuntimeApi<Block, Api = Runtime::RuntimeApi>
+		Client: BlockchainEvents<Block> + ProvideRuntimeApi<Block, Api = Runtime::RuntimeApi> + HeaderBackend<Block>
 			+ Sized + Send + Sync
 			+ CallApiAt<
 				Block,