Fix XcmPaymentApi::query_weight_to_asset_fee version conversion

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/lib.rs

@@ -1423,7 +1423,8 @@ impl_runtime_apis! {
 		fn query_weight_to_asset_fee(weight: Weight, asset: VersionedAssetId) -> Result<u128, XcmPaymentApiError> {
 			let native_asset = xcm_config::TokenLocation::get();
 			let fee_in_native = WeightToFee::weight_to_fee(&weight);
-			match asset.try_as::<AssetId>() {
+			let latest_asset_id: Result<AssetId, ()> = asset.clone().try_into();
+			match latest_asset_id {
 				Ok(asset_id) if asset_id.0 == native_asset => {
 					// for native token
 					Ok(fee_in_native)

cumulus/parachains/runtimes/assets/asset-hub-rococo/tests/tests.rs

@@ -1471,3 +1471,28 @@ fn location_conversion_works() {
 		assert_eq!(got, expected, "{}", tc.description);
 	}
 }
+
+#[test]
+fn calling_payment_api_with_a_lower_version_works() {
+	use xcm::prelude::*;
+	use xcm_runtime_apis::fees::runtime_decl_for_xcm_payment_api::XcmPaymentApiV1;
+
+	ExtBuilder::<Runtime>::default().build().execute_with(|| {
+		let transfer_amount = 100u128;
+		let xcm_to_weigh = Xcm::<RuntimeCall>::builder_unsafe()
+			.withdraw_asset((Here, transfer_amount))
+			.buy_execution((Here, transfer_amount), Unlimited)
+			.deposit_asset(AllCounted(1), [1u8; 32])
+			.build();
+		let versioned_xcm_to_weigh = VersionedXcm::from(xcm_to_weigh.clone().into());
+		let lower_version_xcm_to_weigh =
+			versioned_xcm_to_weigh.into_version(XCM_VERSION - 1).unwrap();
+		let xcm_weight = Runtime::query_xcm_weight(lower_version_xcm_to_weigh);
+		assert!(xcm_weight.is_ok());
+		let native_token = VersionedAssetId::from(AssetId(Parent.into()));
+		let lower_version_native_token = native_token.into_version(XCM_VERSION - 1).unwrap();
+		let execution_fees =
+			Runtime::query_weight_to_asset_fee(xcm_weight.unwrap(), lower_version_native_token);
+		assert!(execution_fees.is_ok());
+	});
+}

cumulus/parachains/runtimes/assets/asset-hub-westend/src/lib.rs

@@ -1539,7 +1539,8 @@ impl_runtime_apis! {
 		fn query_weight_to_asset_fee(weight: Weight, asset: VersionedAssetId) -> Result<u128, XcmPaymentApiError> {
 			let native_asset = xcm_config::WestendLocation::get();
 			let fee_in_native = WeightToFee::weight_to_fee(&weight);
-			match asset.try_as::<AssetId>() {
+			let latest_asset_id: Result<AssetId, ()> = asset.clone().try_into();
+			match latest_asset_id {
 				Ok(asset_id) if asset_id.0 == native_asset => {
 					// for native asset
 					Ok(fee_in_native)

cumulus/parachains/runtimes/assets/asset-hub-westend/tests/tests.rs

@@ -1446,3 +1446,28 @@ fn location_conversion_works() {
 		assert_eq!(got, expected, "{}", tc.description);
 	}
 }
+
+#[test]
+fn calling_payment_api_with_a_lower_version_works() {
+	use xcm::prelude::*;
+	use xcm_runtime_apis::fees::runtime_decl_for_xcm_payment_api::XcmPaymentApiV1;
+
+	ExtBuilder::<Runtime>::default().build().execute_with(|| {
+		let transfer_amount = 100u128;
+		let xcm_to_weigh = Xcm::<RuntimeCall>::builder_unsafe()
+			.withdraw_asset((Here, transfer_amount))
+			.buy_execution((Here, transfer_amount), Unlimited)
+			.deposit_asset(AllCounted(1), [1u8; 32])
+			.build();
+		let versioned_xcm_to_weigh = VersionedXcm::from(xcm_to_weigh.clone().into());
+		let lower_version_xcm_to_weigh =
+			versioned_xcm_to_weigh.into_version(XCM_VERSION - 1).unwrap();
+		let xcm_weight = Runtime::query_xcm_weight(lower_version_xcm_to_weigh);
+		assert!(xcm_weight.is_ok());
+		let native_token = VersionedAssetId::from(AssetId(Parent.into()));
+		let lower_version_native_token = native_token.into_version(XCM_VERSION - 1).unwrap();
+		let execution_fees =
+			Runtime::query_weight_to_asset_fee(xcm_weight.unwrap(), lower_version_native_token);
+		assert!(execution_fees.is_ok());
+	});
+}

polkadot/xcm/xcm-runtime-apis/tests/fee_estimation.rs

@@ -353,3 +353,26 @@ fn dry_run_xcm() {
 		);
 	});
 }
+
+#[test]
+fn calling_payment_api_with_a_lower_version_works() {
+	let transfer_amount = 100u128;
+	let xcm_to_weigh = Xcm::<RuntimeCall>::builder_unsafe()
+		.withdraw_asset((Here, transfer_amount))
+		.buy_execution((Here, transfer_amount), Unlimited)
+		.deposit_asset(AllCounted(1), [1u8; 32])
+		.build();
+	let versioned_xcm_to_weigh = VersionedXcm::from(xcm_to_weigh.clone().into());
+	let lower_version_xcm_to_weigh = versioned_xcm_to_weigh.into_version(XCM_VERSION - 1).unwrap();
+	let client = TestClient;
+	let runtime_api = client.runtime_api();
+	let xcm_weight =
+		runtime_api.query_xcm_weight(H256::zero(), lower_version_xcm_to_weigh).unwrap();
+	assert!(xcm_weight.is_ok());
+	let native_token = VersionedAssetId::from(AssetId(Here.into()));
+	let lower_version_native_token = native_token.into_version(XCM_VERSION - 1).unwrap();
+	let execution_fees = runtime_api
+		.query_weight_to_asset_fee(H256::zero(), xcm_weight.unwrap(), lower_version_native_token)
+		.unwrap();
+	assert!(execution_fees.is_ok());
+}

polkadot/xcm/xcm-runtime-apis/tests/mock.rs

@@ -453,7 +453,8 @@ sp_api::mock_impl_runtime_apis! {
 		}
 
 		fn query_weight_to_asset_fee(weight: Weight, asset: VersionedAssetId) -> Result<u128, XcmPaymentApiError> {
-			match asset.try_as::<AssetId>() {
+			let latest_asset_id: Result<AssetId, ()> = asset.clone().try_into();
+			match latest_asset_id {
 				Ok(asset_id) if asset_id.0 == HereLocation::get() => {
 					Ok(WeightToFee::weight_to_fee(&weight))
 				},

prdoc/pr_6459.prdoc

@@ -0,0 +1,20 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Fix version conversion in XcmPaymentApi::query_weight_to_asset_fee.
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      The `query_weight_to_asset_fee` function of the `XcmPaymentApi` was trying
+      to convert versions in the wrong way.
+      This resulted in all calls made with lower versions failing.
+      The version conversion is now done correctly and these same calls will now succeed.
+
+crates:
+  - name: asset-hub-westend-runtime
+    bump: patch
+  - name: asset-hub-rococo-runtime
+    bump: patch
+  - name: xcm-runtime-apis
+    bump: patch