Make ExecuteBlock::execute_block return the final block header (#8244)

This pr changes the `ExecuteBlock` trait to return the final header that
results from executing the given block.

substrate/frame/executive/src/lib.rs

@@ -119,26 +119,20 @@
 use sp_std::{prelude::*, marker::PhantomData};
 use frame_support::{
 	weights::{GetDispatchInfo, DispatchInfo, DispatchClass},
-	traits::{OnInitialize, OnFinalize, OnRuntimeUpgrade, OffchainWorker},
+	traits::{OnInitialize, OnFinalize, OnRuntimeUpgrade, OffchainWorker, ExecuteBlock},
 	dispatch::PostDispatchInfo,
 };
 use sp_runtime::{
 	generic::Digest, ApplyExtrinsicResult,
 	traits::{
 		self, Header, Zero, One, Checkable, Applyable, CheckEqual, ValidateUnsigned, NumberFor,
-		Block as BlockT, Dispatchable, Saturating,
+		Dispatchable, Saturating,
 	},
 	transaction_validity::{TransactionValidity, TransactionSource},
 };
 use codec::{Codec, Encode};
 use frame_system::DigestOf;
 
-/// Trait that can be used to execute a block.
-pub trait ExecuteBlock<Block: BlockT> {
-	/// Actually execute all transitions for `block`.
-	fn execute_block(block: Block);
-}
-
 pub type CheckedOf<E, C> = <E as Checkable<C>>::Checked;
 pub type CallOf<E, C> = <CheckedOf<E, C> as Applyable>::Call;
 pub type OriginOf<E, C> = <CallOf<E, C> as Dispatchable>::Origin;
@@ -180,8 +174,8 @@ where
 	OriginOf<Block::Extrinsic, Context>: From<Option<System::AccountId>>,
 	UnsignedValidator: ValidateUnsigned<Call=CallOf<Block::Extrinsic, Context>>,
 {
-	fn execute_block(block: Block) {
-		Executive::<System, Block, Context, UnsignedValidator, AllModules>::execute_block(block);
+	fn execute_block(block: Block) -> Block::Header {
+		Executive::<System, Block, Context, UnsignedValidator, AllModules>::execute_block(block)
 	}
 }
 
@@ -318,11 +312,11 @@ where
 	}
 
 	/// Actually execute all transitions for `block`.
-	pub fn execute_block(block: Block) {
+	pub fn execute_block(block: Block) -> Block::Header {
 		sp_io::init_tracing();
 		sp_tracing::within_span! {
-			sp_tracing::info_span!( "execute_block", ?block);
-		{
+			sp_tracing::info_span!("execute_block", ?block);
+
 			Self::initialize_block(block.header());
 
 			// any initial checks
@@ -339,8 +333,8 @@ where
 			}
 
 			// any final checks
-			Self::final_checks(&header);
-		} };
+			Self::final_checks(&header)
+		}
 	}
 
 	/// Execute given extrinsics and take care of post-extrinsics book-keeping.
@@ -412,7 +406,7 @@ where
 		Ok(r.map(|_| ()).map_err(|e| e.error))
 	}
 
-	fn final_checks(header: &System::Header) {
+	fn final_checks(header: &System::Header) -> System::Header {
 		sp_tracing::enter_span!(sp_tracing::Level::TRACE, "final_checks");
 		// remove temporaries
 		let new_header = <frame_system::Module<System>>::finalize();
@@ -438,6 +432,8 @@ where
 			header.extrinsics_root() == new_header.extrinsics_root(),
 			"Transaction trie root must be valid.",
 		);
+
+		new_header
 	}
 
 	/// Check a given signed transaction for validity. This doesn't execute any
@@ -502,7 +498,7 @@ mod tests {
 	use sp_core::H256;
 	use sp_runtime::{
 		generic::{Era, DigestItem}, DispatchError, testing::{Digest, Header, Block},
-		traits::{Header as HeaderT, BlakeTwo256, IdentityLookup},
+		traits::{Header as HeaderT, BlakeTwo256, IdentityLookup, Block as BlockT},
 		transaction_validity::{
 			InvalidTransaction, ValidTransaction, TransactionValidityError, UnknownTransaction
 		},