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// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
//! Cross-Consensus Message format data structures.
use crate::v3::Error as NewError;
use codec::{Decode, Encode};
use core::result;
use scale_info::TypeInfo;
use super::*;
// A simple trait to get the weight of some object.
pub trait GetWeight<W> {
fn weight(&self) -> sp_weights::Weight;
}
#[derive(Copy, Clone, Encode, Decode, Eq, PartialEq, Debug, TypeInfo)]
#[scale_info(replace_segment("staging_xcm", "xcm"))]
pub enum Error {
// Errors that happen due to instructions being executed. These alone are defined in the
// XCM specification.
/// An arithmetic overflow happened.
#[codec(index = 0)]
Overflow,
/// The instruction is intentionally unsupported.
#[codec(index = 1)]
Unimplemented,
/// Origin Register does not contain a value value for a reserve transfer notification.
#[codec(index = 2)]
UntrustedReserveLocation,
/// Origin Register does not contain a value value for a teleport notification.
#[codec(index = 3)]
UntrustedTeleportLocation,
/// `MultiLocation` value too large to descend further.
#[codec(index = 4)]
MultiLocationFull,
/// `MultiLocation` value ascend more parents than known ancestors of local location.
#[codec(index = 5)]
MultiLocationNotInvertible,
/// The Origin Register does not contain a valid value for instruction.
#[codec(index = 6)]
BadOrigin,
/// The location parameter is not a valid value for the instruction.
#[codec(index = 7)]
InvalidLocation,
/// The given asset is not handled.
#[codec(index = 8)]
AssetNotFound,
/// An asset transaction (like withdraw or deposit) failed (typically due to type conversions).
#[codec(index = 9)]
FailedToTransactAsset(#[codec(skip)] &'static str),
/// An asset cannot be withdrawn, potentially due to lack of ownership, availability or rights.
#[codec(index = 10)]
NotWithdrawable,
/// An asset cannot be deposited under the ownership of a particular location.
#[codec(index = 11)]
LocationCannotHold,
/// Attempt to send a message greater than the maximum supported by the transport protocol.
#[codec(index = 12)]
ExceedsMaxMessageSize,
/// The given message cannot be translated into a format supported by the destination.
#[codec(index = 13)]
DestinationUnsupported,
/// Destination is routable, but there is some issue with the transport mechanism.
#[codec(index = 14)]
Transport(#[codec(skip)] &'static str),
/// Destination is known to be unroutable.
#[codec(index = 15)]
Unroutable,
/// Used by `ClaimAsset` when the given claim could not be recognized/found.
#[codec(index = 16)]
UnknownClaim,
/// Used by `Transact` when the functor cannot be decoded.
#[codec(index = 17)]
FailedToDecode,
/// Used by `Transact` to indicate that the given weight limit could be breached by the
/// functor.
#[codec(index = 18)]
MaxWeightInvalid,
/// Used by `BuyExecution` when the Holding Register does not contain payable fees.
#[codec(index = 19)]
NotHoldingFees,
/// Used by `BuyExecution` when the fees declared to purchase weight are insufficient.
#[codec(index = 20)]
TooExpensive,
/// Used by the `Trap` instruction to force an error intentionally. Its code is included.
#[codec(index = 21)]
Trap(u64),
// Errors that happen prior to instructions being executed. These fall outside of the XCM
// spec.
/// XCM version not able to be handled.
UnhandledXcmVersion,
/// Execution of the XCM would potentially result in a greater weight used than weight limit.
WeightLimitReached(Weight),
/// The XCM did not pass the barrier condition for execution.
///
/// The barrier condition differs on different chains and in different circumstances, but
/// generally it means that the conditions surrounding the message were not such that the chain
/// considers the message worth spending time executing. Since most chains lift the barrier to
/// execution on appropriate payment, presentation of an NFT voucher, or based on the message
/// origin, it means that none of those were the case.
Barrier,
/// The weight of an XCM message is not computable ahead of execution.
WeightNotComputable,
}
impl TryFrom<NewError> for Error {
type Error = ();
fn try_from(new_error: NewError) -> result::Result<Error, ()> {
use NewError::*;
Ok(match new_error {
Overflow => Self::Overflow,
Unimplemented => Self::Unimplemented,
UntrustedReserveLocation => Self::UntrustedReserveLocation,
UntrustedTeleportLocation => Self::UntrustedTeleportLocation,
LocationFull => Self::MultiLocationFull,
LocationNotInvertible => Self::MultiLocationNotInvertible,
BadOrigin => Self::BadOrigin,
InvalidLocation => Self::InvalidLocation,
AssetNotFound => Self::AssetNotFound,
FailedToTransactAsset(s) => Self::FailedToTransactAsset(s),
NotWithdrawable => Self::NotWithdrawable,
LocationCannotHold => Self::LocationCannotHold,
ExceedsMaxMessageSize => Self::ExceedsMaxMessageSize,
DestinationUnsupported => Self::DestinationUnsupported,
Transport(s) => Self::Transport(s),
Unroutable => Self::Unroutable,
UnknownClaim => Self::UnknownClaim,
FailedToDecode => Self::FailedToDecode,
MaxWeightInvalid => Self::MaxWeightInvalid,
NotHoldingFees => Self::NotHoldingFees,
TooExpensive => Self::TooExpensive,
Trap(i) => Self::Trap(i),
_ => return Err(()),
})
}
}
impl From<SendError> for Error {
fn from(e: SendError) -> Self {
match e {
SendError::NotApplicable(..) | SendError::Unroutable => Error::Unroutable,
SendError::Transport(s) => Error::Transport(s),
SendError::DestinationUnsupported => Error::DestinationUnsupported,
SendError::ExceedsMaxMessageSize => Error::ExceedsMaxMessageSize,
}
}
}
pub type Result = result::Result<(), Error>;
/// Outcome of an XCM execution.
#[derive(Clone, Encode, Decode, Eq, PartialEq, Debug, TypeInfo)]
#[scale_info(replace_segment("staging_xcm", "xcm"))]
pub enum Outcome {
/// Execution completed successfully; given weight was used.
Complete(Weight),
/// Execution started, but did not complete successfully due to the given error; given weight
/// was used.
Incomplete(Weight, Error),
/// Execution did not start due to the given error.
Error(Error),
}
impl Outcome {
pub fn ensure_complete(self) -> Result {
match self {
Outcome::Complete(_) => Ok(()),
Outcome::Incomplete(_, e) => Err(e),
Outcome::Error(e) => Err(e),
}
}
pub fn ensure_execution(self) -> result::Result<Weight, Error> {
match self {
Outcome::Complete(w) => Ok(w),
Outcome::Incomplete(w, _) => Ok(w),
Outcome::Error(e) => Err(e),
}
}
/// How much weight was used by the XCM execution attempt.
pub fn weight_used(&self) -> Weight {
match self {
Outcome::Complete(w) => *w,
Outcome::Incomplete(w, _) => *w,
Outcome::Error(_) => 0,
}
}
}
/// Type of XCM message executor.
pub trait ExecuteXcm<RuntimeCall> {
/// Execute some XCM `message` from `origin` using no more than `weight_limit` weight. The
/// weight limit is a basic hard-limit and the implementation may place further restrictions or
/// requirements on weight and other aspects.
fn execute_xcm(
origin: impl Into<MultiLocation>,
message: Xcm<RuntimeCall>,
weight_limit: Weight,
) -> Outcome {
let origin = origin.into();
log::debug!(
target: "xcm::execute_xcm",
"origin: {:?}, message: {:?}, weight_limit: {:?}",
origin,
message,
weight_limit,
);
Self::execute_xcm_in_credit(origin, message, weight_limit, 0)
}
/// Execute some XCM `message` from `origin` using no more than `weight_limit` weight.
///
/// Some amount of `weight_credit` may be provided which, depending on the implementation, may
/// allow execution without associated payment.
fn execute_xcm_in_credit(
origin: impl Into<MultiLocation>,
message: Xcm<RuntimeCall>,
weight_limit: Weight,
weight_credit: Weight,
) -> Outcome;
}
impl<C> ExecuteXcm<C> for () {
fn execute_xcm_in_credit(
_origin: impl Into<MultiLocation>,
_message: Xcm<C>,
_weight_limit: Weight,
_weight_credit: Weight,
) -> Outcome {
Outcome::Error(Error::Unimplemented)
}
}
/// Error result value when attempting to send an XCM message.
#[derive(Clone, Encode, Decode, Eq, PartialEq, Debug, scale_info::TypeInfo)]
#[scale_info(replace_segment("staging_xcm", "xcm"))]
pub enum SendError {
/// The message and destination combination was not recognized as being reachable.
///
/// This is not considered fatal: if there are alternative transport routes available, then
/// they may be attempted. For this reason, the destination and message are contained.
NotApplicable(MultiLocation, Xcm<()>),
/// Destination is routable, but there is some issue with the transport mechanism. This is
/// considered fatal.
/// A human-readable explanation of the specific issue is provided.
Transport(#[codec(skip)] &'static str),
/// Destination is known to be unroutable. This is considered fatal.
Unroutable,
/// The given message cannot be translated into a format that the destination can be expected
/// to interpret.
DestinationUnsupported,
/// Message could not be sent due to its size exceeding the maximum allowed by the transport
/// layer.
ExceedsMaxMessageSize,
}
/// Result value when attempting to send an XCM message.
pub type SendResult = result::Result<(), SendError>;
/// Utility for sending an XCM message.
///
/// These can be amalgamated in tuples to form sophisticated routing systems. In tuple format, each
/// router might return `NotApplicable` to pass the execution to the next sender item. Note that
/// each `NotApplicable` might alter the destination and the XCM message for to the next router.
///
///
/// # Example
/// ```rust
/// # use staging_xcm::v2::prelude::*;
/// # use codec::Encode;
///
/// /// A sender that only passes the message through and does nothing.
/// struct Sender1;
/// impl SendXcm for Sender1 {
/// fn send_xcm(destination: impl Into<MultiLocation>, message: Xcm<()>) -> SendResult {
/// return Err(SendError::NotApplicable(destination.into(), message))
/// }
/// }
///
/// /// A sender that accepts a message that has two junctions, otherwise stops the routing.
/// struct Sender2;
/// impl SendXcm for Sender2 {
/// fn send_xcm(destination: impl Into<MultiLocation>, message: Xcm<()>) -> SendResult {
/// let destination = destination.into();
/// if destination.parents == 0 && destination.interior.len() == 2 {
/// Ok(())
/// } else {
/// Err(SendError::Unroutable)
/// }
/// }
/// }
///
/// /// A sender that accepts a message from a parent, passing through otherwise.
/// struct Sender3;
/// impl SendXcm for Sender3 {
/// fn send_xcm(destination: impl Into<MultiLocation>, message: Xcm<()>) -> SendResult {
/// let destination = destination.into();
/// match destination {
/// MultiLocation { parents: 1, interior: Here } => Ok(()),
/// _ => Err(SendError::NotApplicable(destination, message)),
/// }
/// }
/// }
///
/// // A call to send via XCM. We don't really care about this.
/// # fn main() {
/// let call: Vec<u8> = ().encode();
/// let message = Xcm(vec![Instruction::Transact {
/// origin_type: OriginKind::Superuser,
/// require_weight_at_most: 0,
/// call: call.into(),
/// }]);
///
/// assert!(
/// // Sender2 will block this.
/// <(Sender1, Sender2, Sender3) as SendXcm>::send_xcm(Parent, message.clone())
/// .is_err()
/// );
///
/// assert!(
/// // Sender3 will catch this.
/// <(Sender1, Sender3) as SendXcm>::send_xcm(Parent, message.clone())
/// .is_ok()
/// );
/// # }
/// ```
pub trait SendXcm {
/// Send an XCM `message` to a given `destination`.
///
/// If it is not a destination which can be reached with this type but possibly could by others,
/// then it *MUST* return `NotApplicable`. Any other error will cause the tuple implementation
/// to exit early without trying other type fields.
fn send_xcm(destination: impl Into<MultiLocation>, message: Xcm<()>) -> SendResult;
}
#[impl_trait_for_tuples::impl_for_tuples(30)]
impl SendXcm for Tuple {
fn send_xcm(destination: impl Into<MultiLocation>, message: Xcm<()>) -> SendResult {
for_tuples!( #(
// we shadow `destination` and `message` in each expansion for the next one.
let (destination, message) = match Tuple::send_xcm(destination, message) {
Err(SendError::NotApplicable(d, m)) => (d, m),
o @ _ => return o,
};
)* );
Err(SendError::NotApplicable(destination.into(), message))
}
}