Reanchor recipient in to-non-reserve transfer (#787)

* Reanchor recipient in to-non-reserve transfer due to the case where it is overriden by SelfLocation, that could be in relative view

Signed-off-by: Georgi Zlatarev <[email protected]>

* Handle error

Signed-off-by: Georgi Zlatarev <[email protected]>

* Clippy

Signed-off-by: Georgi Zlatarev <[email protected]>

* Add test case

Signed-off-by: Georgi Zlatarev <[email protected]>

* Use relative para chain for test

Signed-off-by: Georgi Zlatarev <[email protected]>

* Remove println

Signed-off-by: Georgi Zlatarev <[email protected]>

* Reanchor before execute_and_send_reserve_kind_xcm instead of in transfer_to_non_reserve

Signed-off-by: Georgi Zlatarev <[email protected]>

* Edit readme

Signed-off-by: Georgi Zlatarev <[email protected]>

Author: ghzlatarev

xtokens/README.md

@@ -71,6 +71,6 @@ parameter_type_with_key! {
 }
 ```
 
-Notice the implementation for now also rely on `SelfLocation` which already in `xtokens` config. The `SelfLocation` current is `(1, Parachain(id))` refer to sender parachain. If parachain set `SelfLocation` to (0, Here), it'll be error in this case.
+Notice the implementation for now also relies on `SelfLocation` which is already in `xtokens` config. The `SelfLocation` is currently set to absolute view `(1, Parachain(id))` and refers to the sender parachain. However `SelfLocation` set to relative view `(0, Here)` will also work.
 
 We use `SelfLocation` to fund fee to sender's parachain sovereign account on destination parachain, which asset is originated from sender account on sender parachain. This means if user setup too much fee, the fee will not returned to user, instead deposit to sibling parachain sovereign account on destination parachain.

xtokens/src/lib.rs

@@ -561,6 +561,15 @@ pub mod module {
 				let asset_to_fee_reserve = subtract_fee(&fee, min_xcm_fee);
 				assets_to_fee_reserve.push(asset_to_fee_reserve.clone());
 
+				let mut override_recipient = T::SelfLocation::get();
+				if override_recipient == MultiLocation::here() {
+					let dest_chain_part = dest.chain_part().ok_or(Error::<T>::InvalidDest)?;
+					let ancestry = T::LocationInverter::ancestry();
+					let _ = override_recipient
+						.reanchor(&dest_chain_part, &ancestry)
+						.map_err(|_| Error::<T>::CannotReanchor);
+				}
+
 				// First xcm sent to fee reserve chain and routed to dest chain.
 				// We can use `MinXcmFee` configuration to decide which target parachain use
 				// teleport. But as current there's only one case which is Parachain send back
@@ -571,7 +580,7 @@ pub mod module {
 					asset_to_fee_reserve,
 					fee_reserve,
 					&dest,
-					Some(T::SelfLocation::get()),
+					Some(override_recipient),
 					dest_weight,
 					true,
 				)?;

xtokens/src/mock/para_relative_view.rs

@@ -307,6 +307,7 @@ parameter_type_with_key! {
 		#[allow(clippy::match_ref_pats)] // false positive
 		match (location.parents, location.first_interior()) {
 			(1, Some(Parachain(2))) => Some(40),
+			(1, Some(Parachain(3))) => Some(40),
 			_ => None,
 		}
 	};

xtokens/src/tests.rs

@@ -705,6 +705,69 @@ fn sending_sibling_asset_to_reserve_sibling_with_relay_fee_works() {
 	});
 }
 
+#[test]
+fn sending_sibling_asset_to_reserve_sibling_with_relay_fee_works_with_relative_self_location() {
+	TestNet::reset();
+
+	ParaD::execute_with(|| {
+		assert_ok!(ParaTokens::deposit(CurrencyId::C, &ALICE, 1_000));
+	});
+
+	ParaC::execute_with(|| {
+		assert_ok!(ParaTeleportTokens::deposit(CurrencyId::C, &sibling_d_account(), 1_000));
+	});
+
+	Relay::execute_with(|| {
+		let _ = RelayBalances::deposit_creating(&para_d_account(), 1_000);
+	});
+
+	let fee_amount: u128 = 200;
+	let weight: u128 = 50;
+	let dest_weight: u128 = 40;
+
+	ParaD::execute_with(|| {
+		assert_ok!(ParaRelativeXTokens::transfer_multicurrencies(
+			Some(ALICE).into(),
+			vec![(CurrencyId::C, 450), (CurrencyId::R, fee_amount)],
+			1,
+			Box::new(
+				(
+					Parent,
+					Parachain(3),
+					Junction::AccountId32 {
+						network: NetworkId::Any,
+						id: BOB.into(),
+					},
+				)
+					.into()
+			),
+			weight as u64,
+		));
+		assert_eq!(550, ParaRelativeTokens::free_balance(CurrencyId::C, &ALICE));
+		assert_eq!(
+			1000 - fee_amount,
+			ParaRelativeTokens::free_balance(CurrencyId::R, &ALICE)
+		);
+	});
+
+	Relay::execute_with(|| {
+		assert_eq!(
+			1000 - (fee_amount - dest_weight),
+			RelayBalances::free_balance(&para_d_account())
+		);
+	});
+
+	ParaC::execute_with(|| {
+		assert_eq!(
+			fee_amount - dest_weight * 4,
+			ParaTeleportTokens::free_balance(CurrencyId::R, &sibling_d_account())
+		);
+
+		assert_eq!(450, ParaTeleportTokens::free_balance(CurrencyId::C, &BOB));
+		assert_eq!(0, ParaTeleportTokens::free_balance(CurrencyId::R, &BOB));
+	});
+}
+
 #[test]
 fn sending_sibling_asset_to_reserve_sibling_with_relay_fee_not_enough() {
 	TestNet::reset();