asset_test_utils/
xcm_helpers.rs

1// Copyright (C) Parity Technologies (UK) Ltd.
2// This file is part of Cumulus.
3// SPDX-License-Identifier: Apache-2.0
4
5// Licensed under the Apache License, Version 2.0 (the "License");
6// you may not use this file except in compliance with the License.
7// You may obtain a copy of the License at
8//
9// 	http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing, software
12// distributed under the License is distributed on an "AS IS" BASIS,
13// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14// See the License for the specific language governing permissions and
15// limitations under the License.
16
17//! Helpers for calculating XCM delivery fees.
18
19use xcm::latest::prelude::*;
20
21/// Returns the delivery fees amount for pallet xcm's `teleport_assets` extrinsics.
22/// Because it returns only a `u128`, it assumes delivery fees are only paid
23/// in one asset and that asset is known.
24pub fn teleport_assets_delivery_fees<S: SendXcm>(
25	assets: Assets,
26	fee_asset_item: u32,
27	weight_limit: WeightLimit,
28	beneficiary: Location,
29	destination: Location,
30) -> u128 {
31	let message = teleport_assets_dummy_message(assets, fee_asset_item, weight_limit, beneficiary);
32	get_fungible_delivery_fees::<S>(destination, message)
33}
34
35/// Returns the delivery fees amount for a query response as a result of the execution
36/// of a `ExpectError` instruction with no error.
37pub fn query_response_delivery_fees<S: SendXcm>(querier: Location) -> u128 {
38	// Message to calculate delivery fees, it's encoded size is what's important.
39	// This message reports that there was no error, if an error is reported, the encoded size would
40	// be different.
41	let message = Xcm(vec![
42		SetFeesMode { jit_withdraw: true },
43		QueryResponse {
44			query_id: 0, // Dummy query id
45			response: Response::ExecutionResult(None),
46			max_weight: Weight::zero(),
47			querier: Some(querier.clone()),
48		},
49		SetTopic([0u8; 32]), // Dummy topic
50	]);
51	get_fungible_delivery_fees::<S>(querier, message)
52}
53
54/// Returns the delivery fees amount for the execution of `PayOverXcm`
55pub fn pay_over_xcm_delivery_fees<S: SendXcm>(
56	interior: Junctions,
57	destination: Location,
58	beneficiary: Location,
59	asset: Asset,
60) -> u128 {
61	// This is a dummy message.
62	// The encoded size is all that matters for delivery fees.
63	let message = Xcm(vec![
64		DescendOrigin(interior),
65		UnpaidExecution { weight_limit: Unlimited, check_origin: None },
66		SetAppendix(Xcm(vec![
67			SetFeesMode { jit_withdraw: true },
68			ReportError(QueryResponseInfo {
69				destination: destination.clone(),
70				query_id: 0,
71				max_weight: Weight::zero(),
72			}),
73		])),
74		TransferAsset { beneficiary, assets: vec![asset].into() },
75	]);
76	get_fungible_delivery_fees::<S>(destination, message)
77}
78
79/// Approximates the actual message sent by the teleport extrinsic.
80/// The assets are not reanchored and the topic is a dummy one.
81/// However, it should have the same encoded size, which is what matters for delivery fees.
82/// Also has same encoded size as the one created by the reserve transfer assets extrinsic.
83fn teleport_assets_dummy_message(
84	assets: Assets,
85	fee_asset_item: u32,
86	weight_limit: WeightLimit,
87	beneficiary: Location,
88) -> Xcm<()> {
89	Xcm(vec![
90		ReceiveTeleportedAsset(assets.clone()), // Same encoded size as `ReserveAssetDeposited`
91		ClearOrigin,
92		BuyExecution { fees: assets.get(fee_asset_item as usize).unwrap().clone(), weight_limit },
93		DepositAsset { assets: Wild(AllCounted(assets.len() as u32)), beneficiary },
94		SetTopic([0u8; 32]), // Dummy topic
95	])
96}
97
98/// Given a message, a sender, and a destination, it returns the delivery fees
99fn get_fungible_delivery_fees<S: SendXcm>(destination: Location, message: Xcm<()>) -> u128 {
100	let delivery_fees = match validate_send::<S>(destination, message) {
101		Ok((_, delivery_fees)) => delivery_fees,
102		Err(e) => unreachable!("message can be sent - {:?}; qed", e),
103	};
104	if let Some(delivery_fee) = delivery_fees.inner().first() {
105		let Fungible(delivery_fee_amount) = delivery_fee.fun else {
106			unreachable!("asset is fungible; qed");
107		};
108		delivery_fee_amount
109	} else {
110		0
111	}
112}
asset_test_utils/xcm_helpers.rs

asset_test_utils/
xcm_helpers.rs
