use complex transactions on RBH/WBH bridge hubs (#1893)

bridges/relays/client-substrate/src/calls.rs

@@ -31,6 +31,15 @@ pub enum SystemCall {
 	remark(Vec<u8>),
 }
 
+/// A minimized version of `pallet-utility::Call` that can be used without a runtime.
+#[derive(Encode, Decode, Debug, PartialEq, Eq, Clone, TypeInfo)]
+#[allow(non_camel_case_types)]
+pub enum UtilityCall<Call> {
+	/// `pallet-utility::Call::batch_all`
+	#[codec(index = 2)]
+	batch_all(Vec<Call>),
+}
+
 /// A minimized version of `pallet-sudo::Call` that can be used without a runtime.
 #[derive(Encode, Decode, Debug, PartialEq, Eq, Clone, TypeInfo)]
 #[allow(non_camel_case_types)]

bridges/relays/client-substrate/src/chain.rs

@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
 
+use crate::calls::UtilityCall;
+
 use bp_messages::MessageNonce;
 use bp_runtime::{
 	Chain as ChainBase, EncodedOrDecodedCall, HashOf, Parachain as ParachainBase, TransactionEra,
@@ -276,6 +278,21 @@ where
 	}
 }
 
+/// Structure that implements `UtilityPalletProvider` based on a call conversion.
+pub struct MockedRuntimeUtilityPallet<Call> {
+	_phantom: std::marker::PhantomData<Call>,
+}
+
+impl<C, Call> UtilityPallet<C> for MockedRuntimeUtilityPallet<Call>
+where
+	C: Chain,
+	C::Call: From<UtilityCall<C::Call>>,
+{
+	fn build_batch_call(calls: Vec<C::Call>) -> C::Call {
+		UtilityCall::batch_all(calls).into()
+	}
+}
+
 /// Substrate-based chain that uses `pallet-utility`.
 pub trait ChainWithUtilityPallet: Chain {
 	/// The utility pallet provider.

bridges/relays/client-substrate/src/lib.rs

@@ -36,8 +36,8 @@ pub use crate::{
 	chain::{
 		AccountKeyPairOf, BlockWithJustification, CallOf, Chain, ChainWithBalances,
 		ChainWithGrandpa, ChainWithMessages, ChainWithTransactions, ChainWithUtilityPallet,
-		FullRuntimeUtilityPallet, Parachain, RelayChain, SignParam, TransactionStatusOf,
-		UnsignedTransaction, UtilityPallet,
+		FullRuntimeUtilityPallet, MockedRuntimeUtilityPallet, Parachain, RelayChain, SignParam,
+		TransactionStatusOf, UnsignedTransaction, UtilityPallet,
 	},
 	client::{
 		is_ancient_block, ChainRuntimeVersion, Client, OpaqueGrandpaAuthoritiesSet,