Contracts: Add XCM traits to interface with contracts (#2086)
We are introducing a new set of `XcmController` traits (final name yet
to be determined).
These traits are implemented by `pallet-xcm` and allows other pallets,
such as `pallet_contracts`, to rely on these traits instead of tight
coupling them to `pallet-xcm`.
Using only the existing Xcm traits would mean duplicating the logic from
`pallet-xcm` in these other pallets, which we aim to avoid. Our
objective is to ensure that when these APIs are called from
`pallet-contracts`, they produce the exact same outcomes as if called
directly from `pallet-xcm`.
The other benefits is that we can also expose return values to
`pallet-contracts` instead of just calling `pallet-xcm` dispatchable and
getting a `DispatchResult` back.
See traits integration in this PR
https://github.com/paritytech/polkadot-sdk/pull/1248, where the traits
are used as follow to define and implement `pallet-contracts` Config.
```rs
// Contracts config:
pub trait Config: frame_system::Config {
// ...
/// A type that exposes XCM APIs, allowing contracts to interact with other parachains, and
/// execute XCM programs.
type Xcm: xcm_executor::traits::Controller<
OriginFor<Self>,
<Self as frame_system::Config>::RuntimeCall,
BlockNumberFor<Self>,
>;
}
// implementation
impl pallet_contracts::Config for Runtime {
// ...
type Xcm = pallet_xcm::Pallet<Self>;
}
```
---------
Co-authored-by: Alexander Theißen <[email protected]>
Co-authored-by: command-bot <>
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