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https://github.com/pezkuwichain/pezkuwi-subxt.git
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Pavel Orlov
3c972fc19e
The PR provides API for obtaining: - the weight required to execute an XCM message, - a list of acceptable `AssetId`s for message execution payment, - the cost of the weight in the specified acceptable `AssetId`. It is meant to address an issue where one has to guess how much fee to pay for execution. Also, at the moment, a client has to guess which assets are acceptable for fee execution payment. See the related issue https://github.com/paritytech/polkadot-sdk/issues/690. With this API, a client is supposed to query the list of the supported asset IDs (in the XCM version format the client understands), weigh the XCM program the client wants to execute and convert the weight into one of the acceptable assets. Note that the client is supposed to know what program will be executed on what chains. However, having a small companion JS library for the pallet-xcm and xtokens should be enough to determine what XCM programs will be executed and where (since these pallets compose a known small set of programs). ```Rust pub trait XcmPaymentApi<Call> where Call: Codec, { /// Returns a list of acceptable payment assets. /// /// # Arguments /// /// * `xcm_version`: Version. fn query_acceptable_payment_assets(xcm_version: Version) -> Result<Vec<VersionedAssetId>, Error>; /// Returns a weight needed to execute a XCM. /// /// # Arguments /// /// * `message`: `VersionedXcm`. fn query_xcm_weight(message: VersionedXcm<Call>) -> Result<Weight, Error>; /// Converts a weight into a fee for the specified `AssetId`. /// /// # Arguments /// /// * `weight`: convertible `Weight`. /// * `asset`: `VersionedAssetId`. fn query_weight_to_asset_fee(weight: Weight, asset: VersionedAssetId) -> Result<u128, Error>; /// Get delivery fees for sending a specific `message` to a `destination`. /// These always come in a specific asset, defined by the chain. /// /// # Arguments /// * `message`: The message that'll be sent, necessary because most delivery fees are based on the /// size of the message. /// * `destination`: The destination to send the message to. Different destinations may use /// different senders that charge different fees. fn query_delivery_fees(destination: VersionedLocation, message: VersionedXcm<()>) -> Result<VersionedAssets, Error>; } ``` An [example](https://gist.github.com/PraetorP/4bc323ff85401abe253897ba990ec29d) of a client side code. --------- Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com> Co-authored-by: Adrian Catangiu <adrian@parity.io> Co-authored-by: Daniel Shiposha <mrshiposha@gmail.com>
27 lines
1.4 KiB
Plaintext
27 lines
1.4 KiB
Plaintext
# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
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# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
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title: "XCM fee payment API"
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doc:
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- audience: Runtime Dev
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description: |
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A runtime API was added for estimating the fees required for XCM execution and delivery.
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This is the basic building block needed for UIs to accurately estimate fees.
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An example implementation is shown in the PR. Ideally it's simple to implement, you only need to call existing parts of your XCM config.
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The API looks like so:
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```rust
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fn query_acceptable_payment_assets(xcm_version: Version) -> Result<Vec<VersionedAssetId>, Error>;
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fn query_xcm_weight(message: VersionedXcm<Call>) -> Result<Weight, Error>;
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fn query_weight_to_asset_fee(weight: Weight, asset: VersionedAssetId) -> Result<u128, Error>;
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fn query_delivery_fees(destination: VersionedLocation, message: VersionedXcm<()>) -> Result<VersionedAssets, Error>;
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```
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The first three relate to XCM execution fees, given an XCM, you can query its weight, then which assets are acceptable for buying weight and convert weight to a number of those assets.
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The last one takes in a destination and a message you want to send from the runtime you're executing this on, it will give you the delivery fees.
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crates:
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- name: xcm-fee-payment-runtime-api
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- name: rococo-runtime
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- name: westend-runtime
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