Fixes

pallets/dmp-queue/src/lib.rs

@@ -422,9 +422,16 @@ mod tests {
 
 	pub struct MockExec;
 	impl ExecuteXcm<Call> for MockExec {
+		type Prepared = Weightless;
+
+		fn prepare(message: Xcm<()>) -> Result<Self::Prepared, Xcm<Call>> {
+			Err(message)
+		}
+
 		fn execute_xcm_in_credit(
 			_origin: impl Into<MultiLocation>,
 			message: Xcm,
+			_hash: XcmHash,
 			weight_limit: Weight,
 			_credit: Weight,
 		) -> Outcome {
@@ -442,6 +449,10 @@ mod tests {
 			TRACE.with(|q| q.borrow_mut().push((message, o.clone())));
 			o
 		}
+
+		fn charge_fees(_location: impl Into<MultiLocation>, _fees: MultiAssets) -> XcmResult {
+			Err(XcmError::Unimplemented)
+		}
 	}
 
 	impl Config for Test {

pallets/xcmp-queue/Cargo.toml

@@ -13,6 +13,7 @@ scale-info = { version = "2.0.0", default-features = false, features = ["derive"
 # Substrate
 frame-support = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 frame-system = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+sp-io = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 sp-runtime = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 sp-std = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 
@@ -30,7 +31,6 @@ frame-benchmarking = { default-features = false, optional = true, git = "https:/
 
 # Substrate
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
-sp-io = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-balances = { git = "https://github.com/paritytech/substrate", branch = "master" }
 
 # Polkadot
@@ -48,6 +48,7 @@ std = [
 	"frame-support/std",
 	"frame-system/std",
 	"log/std",
+	"sp-io/std",
 	"sp-runtime/std",
 	"sp-std/std",
 	"xcm-executor/std",

pallets/xcmp-queue/src/lib.rs

@@ -1079,26 +1079,41 @@ impl<T: Config> XcmpMessageSource for Pallet<T> {
 
 /// Xcm sender for sending to a sibling parachain.
 impl<T: Config> SendXcm for Pallet<T> {
-	fn send_xcm(dest: impl Into<MultiLocation>, msg: Xcm<()>) -> SendResult {
-		let dest = dest.into();
+	type Ticket = (ParaId, VersionedXcm<()>);
 
-		match &dest {
+	fn validate(
+		dest: &mut Option<MultiLocation>,
+		msg: &mut Option<Xcm<()>>,
+	) -> SendResult<(ParaId, VersionedXcm<()>)> {
+		let d = dest.take().ok_or(SendError::MissingArgument)?;
+		let xcm = msg.take().ok_or(SendError::MissingArgument)?;
+
+		match &d {
 			// An HRMP message for a sibling parachain.
 			MultiLocation { parents: 1, interior: X1(Parachain(id)) } => {
-				let versioned_xcm = T::VersionWrapper::wrap_version(&dest, msg)
+				let versioned_xcm = T::VersionWrapper::wrap_version(&d, xcm)
 					.map_err(|()| SendError::DestinationUnsupported)?;
-				let hash = T::Hashing::hash_of(&versioned_xcm);
-				Self::send_fragment(
-					(*id).into(),
-					XcmpMessageFormat::ConcatenatedVersionedXcm,
-					versioned_xcm,
-				)
-				.map_err(|e| SendError::Transport(<&'static str>::from(e)))?;
-				Self::deposit_event(Event::XcmpMessageSent(Some(hash)));
-				Ok(hash)
+				Ok(((*id).into(), versioned_xcm))
 			},
 			// Anything else is unhandled. This includes a message this is meant for us.
-			_ => Err(SendError::CannotReachDestination(dest, msg)),
+			_ => {
+				*dest = Some(d);
+				Err(SendError::NotApplicable)
+			}
+		}
+	}
+
+	fn deliver((id, xcm): (ParaId, VersionedXcm<()>)) -> Result<XcmHash, SendError> {
+		let hash = xcm.using_encoded(sp_io::hashing::blake2_256);
+
+		match Self::send_fragment(id, XcmpMessageFormat::ConcatenatedVersionedXcm, xcm) {
+			Ok(_) => {
+				Self::deposit_event(Event::XcmpMessageSent(Some(hash)));
+				Ok(hash)
+			}
+			Err(e) => {
+				Err(SendError::Transport(<&'static str>::from(e)))
+			}
 		}
 	}
 }