The XCM builder pattern lets you build xcms like so:
```rust
let xcm = Xcm::builder()
.withdraw_asset((Parent, 100u128).into())
.buy_execution((Parent, 1u128).into())
.deposit_asset(All.into(), AccountId32 { id: [0u8; 32], network: None }.into())
.build();
```
All the `.into()` become quite annoying to have to write.
I accepted `impl Into<T>` instead of `T` in the generated methods from
the macro.
Now the previous example can be simplified as follows:
```rust
let xcm = Xcm::builder()
.withdraw_asset((Parent, 100u128))
.buy_execution((Parent, 1u128))
.deposit_asset(All, [0u8; 32])
.build();
```
---------
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: command-bot <>
Co-authored-by: Adrian Catangiu <adrian@parity.io>
# Note for reviewer
Most changes are just syntax changes necessary for the new version.
Most important files should be the ones under the `xcm` folder.
# Description
Added XCMv4.
## Removed `Multi` prefix
The following types have been renamed:
- MultiLocation -> Location
- MultiAsset -> Asset
- MultiAssets -> Assets
- InteriorMultiLocation -> InteriorLocation
- MultiAssetFilter -> AssetFilter
- VersionedMultiAsset -> VersionedAsset
- WildMultiAsset -> WildAsset
- VersionedMultiLocation -> VersionedLocation
In order to fix a name conflict, the `Assets` in `xcm-executor` were
renamed to `HoldingAssets`, as they represent assets in holding.
## Removed `Abstract` asset id
It was not being used anywhere and this simplifies the code.
Now assets are just constructed as follows:
```rust
let asset: Asset = (AssetId(Location::new(1, Here)), 100u128).into();
```
No need for specifying `Concrete` anymore.
## Outcome is now a named fields struct
Instead of
```rust
pub enum Outcome {
Complete(Weight),
Incomplete(Weight, Error),
Error(Error),
}
```
we now have
```rust
pub enum Outcome {
Complete { used: Weight },
Incomplete { used: Weight, error: Error },
Error { error: Error },
}
```
## Added Reanchorable trait
Now both locations and assets implement this trait, making it easier to
reanchor both.
## New syntax for building locations and junctions
Now junctions are built using the following methods:
```rust
let location = Location {
parents: 1,
interior: [Parachain(1000), PalletInstance(50), GeneralIndex(1984)].into()
};
```
or
```rust
let location = Location::new(1, [Parachain(1000), PalletInstance(50), GeneralIndex(1984)]);
```
And they are matched like so:
```rust
match location.unpack() {
(1, [Parachain(id)]) => ...
(0, Here) => ...,
(1, [_]) => ...,
}
```
This syntax is mandatory in v4, and has been also implemented for v2 and
v3 for easier migration.
This was needed to make all sizes smaller.
# TODO
- [x] Scaffold v4
- [x] Port github.com/paritytech/polkadot/pull/7236
- [x] Remove `Multi` prefix
- [x] Remove `Abstract` asset id
---------
Co-authored-by: command-bot <>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>
Adding on top of the new builder pattern for creating XCM programs, I'm
adding some more APIs:
```rust
let paying_fees: Xcm<()> = Xcm::builder() // Only allow paying for fees
.withdraw_asset() // First instruction has to load the holding register
.buy_execution() // Second instruction has to be `buy_execution`
.build();
let paying_fees_invalid: Xcm<()> = Xcm::builder()
.withdraw_asset()
.build(); // Invalid, need to pay for fees
let not_paying_fees: Xcm<()> = Xcm::builder_unpaid()
.unpaid_execution() // Needed
.withdraw_asset()
.deposit_asset()
.build();
let all_goes: Xcm<()> = Xcm::builder_unsafe() // You can do anything
.withdraw_asset()
.deposit_asset()
.build();
```
The invalid bits are because the methods don't even exist on the types
that you'd want to call them on.
---------
Co-authored-by: command-bot <>
Added a proc macro to be able to write XCMs using the builder pattern.
This means we go from having to do this:
```rust
let message: Xcm<()> = Xcm(vec![
WithdrawAsset(assets),
BuyExecution { fees: asset, weight_limit: Unlimited },
DepositAsset { assets, beneficiary },
]);
```
to this:
```rust
let message: Xcm<()> = Xcm::builder()
.withdraw_asset(assets)
.buy_execution(asset, Unlimited),
.deposit_asset(assets, beneficiary)
.build();
```
---------
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>
Co-authored-by: command-bot <>
Francisco Aguirre