evm foreign asset: change_asset_location should not erase already exi…

…sting location (#2925)

* fix: change evm foreign asset location: ensure new location not exist

* rust test: cover error LocationAlreadyExists

pallets/moonbeam-foreign-assets/src/lib.rs

@@ -341,6 +341,11 @@ pub mod pallet {
 			let previous_location =
 				AssetsById::<T>::get(&asset_id).ok_or(Error::<T>::AssetDoesNotExist)?;
 
+			ensure!(
+				!AssetsByLocation::<T>::contains_key(&new_xcm_location),
+				Error::<T>::LocationAlreadyExists
+			);
+
 			// Remove previous foreign asset info
 			let (_asset_id, asset_status) = AssetsByLocation::<T>::take(&previous_location)
 				.ok_or(Error::<T>::CorruptedStorageOrphanLocation)?;

pallets/moonbeam-foreign-assets/src/tests.rs

@@ -210,3 +210,45 @@ fn test_asset_id_non_existent_error() {
 		);
 	});
 }
+
+#[test]
+fn test_location_already_exist_error() {
+	ExtBuilder::default().build().execute_with(|| {
+		// Setup: create a first foreign asset taht we will try to override
+		assert_ok!(EvmForeignAssets::create_foreign_asset(
+			RuntimeOrigin::root(),
+			1,
+			Location::parent(),
+			18,
+			encode_ticker("MTT"),
+			encode_token_name("Mytoken"),
+		));
+
+		assert_noop!(
+			EvmForeignAssets::create_foreign_asset(
+				RuntimeOrigin::root(),
+				2,
+				Location::parent(),
+				18,
+				encode_ticker("MTT"),
+				encode_token_name("Mytoken"),
+			),
+			Error::<Test>::LocationAlreadyExists
+		);
+
+		// Setup: create a second foreign asset that will try to override the first one
+		assert_ok!(EvmForeignAssets::create_foreign_asset(
+			RuntimeOrigin::root(),
+			2,
+			Location::new(2, *&[]),
+			18,
+			encode_ticker("MTT"),
+			encode_token_name("Mytoken"),
+		));
+
+		assert_noop!(
+			EvmForeignAssets::change_xcm_location(RuntimeOrigin::root(), 2, Location::parent()),
+			Error::<Test>::LocationAlreadyExists
+		);
+	});
+}