diff --git a/polkadot/xcm/xcm-builder/src/lib.rs b/polkadot/xcm/xcm-builder/src/lib.rs
index 3d68d8ed16ae1459f7ac2dd39f1df80ecb44131e..e23412a97ebcb3e6f2999d0f48d555e53d02503e 100644
--- a/polkadot/xcm/xcm-builder/src/lib.rs
+++ b/polkadot/xcm/xcm-builder/src/lib.rs
@@ -132,11 +132,13 @@ pub use routing::{
mod transactional;
pub use transactional::FrameTransactionalProcessor;
+#[allow(deprecated)]
+pub use universal_exports::UnpaidLocalExporter;
mod universal_exports;
pub use universal_exports::{
ensure_is_remote, BridgeBlobDispatcher, BridgeMessage, DispatchBlob, DispatchBlobError,
- ExporterFor, HaulBlob, HaulBlobError, HaulBlobExporter, NetworkExportTable,
- NetworkExportTableItem, SovereignPaidRemoteExporter, UnpaidLocalExporter, UnpaidRemoteExporter,
+ ExporterFor, HaulBlob, HaulBlobError, HaulBlobExporter, LocalExporter, NetworkExportTable,
+ NetworkExportTableItem, SovereignPaidRemoteExporter, UnpaidRemoteExporter,
};
mod weight;
diff --git a/polkadot/xcm/xcm-builder/src/tests/bridging/local_para_para.rs b/polkadot/xcm/xcm-builder/src/tests/bridging/local_para_para.rs
index ea584bf9d485a25c38ce0b673259b6ed8df7368f..5e930fe575c2b07c3c8d172f478d7f20ff519e76 100644
--- a/polkadot/xcm/xcm-builder/src/tests/bridging/local_para_para.rs
+++ b/polkadot/xcm/xcm-builder/src/tests/bridging/local_para_para.rs
@@ -28,7 +28,7 @@ parameter_types! {
type TheBridge =
TestBridge<BridgeBlobDispatcher<TestRemoteIncomingRouter, RemoteUniversalLocation, ()>>;
type Router = TestTopic<
- UnpaidLocalExporter<
+ LocalExporter<
HaulBlobExporter<TheBridge, RemoteNetwork, AlwaysLatest, Price>,
UniversalLocation,
>,
diff --git a/polkadot/xcm/xcm-builder/src/tests/bridging/local_relay_relay.rs b/polkadot/xcm/xcm-builder/src/tests/bridging/local_relay_relay.rs
index 38ffe2532d580a017efc21043e7313028700c046..a41f09721812a99f71fdcb58345e265472b163c6 100644
--- a/polkadot/xcm/xcm-builder/src/tests/bridging/local_relay_relay.rs
+++ b/polkadot/xcm/xcm-builder/src/tests/bridging/local_relay_relay.rs
@@ -28,7 +28,7 @@ parameter_types! {
type TheBridge =
TestBridge<BridgeBlobDispatcher<TestRemoteIncomingRouter, RemoteUniversalLocation, ()>>;
type Router = TestTopic<
- UnpaidLocalExporter<
+ LocalExporter<
HaulBlobExporter<TheBridge, RemoteNetwork, AlwaysLatest, Price>,
UniversalLocation,
>,
diff --git a/polkadot/xcm/xcm-builder/src/tests/bridging/mod.rs b/polkadot/xcm/xcm-builder/src/tests/bridging/mod.rs
index 767575e7f2dd9efa29cc1441a8cc2bf2cdaf3d19..90ad9921d65a13b8b5590507d0a7c36ba79b063a 100644
--- a/polkadot/xcm/xcm-builder/src/tests/bridging/mod.rs
+++ b/polkadot/xcm/xcm-builder/src/tests/bridging/mod.rs
@@ -209,7 +209,7 @@ impl<Local: Get<Junctions>, Remote: Get<Junctions>, RemoteExporter: ExportXcm> S
let origin = Local::get().relative_to(&Remote::get());
AllowUnpaidFrom::set(vec![origin.clone()]);
set_exporter_override(price::<RemoteExporter>, deliver::<RemoteExporter>);
- // The we execute it:
+ // Then we execute it:
let mut id = fake_id();
let outcome = XcmExecutor::<TestConfig>::prepare_and_execute(
origin,
diff --git a/polkadot/xcm/xcm-builder/src/universal_exports.rs b/polkadot/xcm/xcm-builder/src/universal_exports.rs
index 6b3c3adf737dbb6e938d59383c5100041c493d52..e215aea3ab6858a0bcecd5b952cb4fd1384f52a9 100644
--- a/polkadot/xcm/xcm-builder/src/universal_exports.rs
+++ b/polkadot/xcm/xcm-builder/src/universal_exports.rs
@@ -16,6 +16,8 @@
//! Traits and utilities to help with origin mutation and bridging.
+#![allow(deprecated)]
+
use crate::InspectMessageQueues;
use alloc::{vec, vec::Vec};
use codec::{Decode, Encode};
@@ -58,6 +60,8 @@ pub fn ensure_is_remote(
/// that the message sending cannot be abused in any way.
///
/// This is only useful when the local chain has bridging capabilities.
+#[deprecated(note = "Will be removed after July 2025; It uses hard-coded channel `0`, \
+ use `xcm_builder::LocalExporter` directly instead.")]
pub struct UnpaidLocalExporter<Exporter, UniversalLocation>(
PhantomData<(Exporter, UniversalLocation)>,
);
@@ -100,6 +104,54 @@ impl<Exporter: ExportXcm, UniversalLocation: Get<InteriorLocation>> SendXcm
fn ensure_successful_delivery(_: Option<Location>) {}
}
+/// Implementation of `SendXcm` which uses the given `ExportXcm` implementation in order to forward
+/// the message over a bridge.
+///
+/// This is only useful when the local chain has bridging capabilities.
+pub struct LocalExporter<Exporter, UniversalLocation>(PhantomData<(Exporter, UniversalLocation)>);
+impl<Exporter: ExportXcm, UniversalLocation: Get<InteriorLocation>> SendXcm
+ for LocalExporter<Exporter, UniversalLocation>
+{
+ type Ticket = Exporter::Ticket;
+
+ fn validate(
+ dest: &mut Option<Location>,
+ msg: &mut Option<Xcm<()>>,
+ ) -> SendResult<Exporter::Ticket> {
+ // This `clone` ensures that `dest` is not consumed in any case.
+ let d = dest.clone().take().ok_or(MissingArgument)?;
+ let universal_source = UniversalLocation::get();
+ let devolved = ensure_is_remote(universal_source.clone(), d).map_err(|_| NotApplicable)?;
+ let (remote_network, remote_location) = devolved;
+ let xcm = msg.take().ok_or(MissingArgument)?;
+
+ let hash =
+ (Some(Location::here()), &remote_location).using_encoded(sp_io::hashing::blake2_128);
+ let channel = u32::decode(&mut hash.as_ref()).unwrap_or(0);
+
+ validate_export::<Exporter>(
+ remote_network,
+ channel,
+ universal_source,
+ remote_location,
+ xcm.clone(),
+ )
+ .inspect_err(|err| {
+ if let NotApplicable = err {
+ // We need to make sure that msg is not consumed in case of `NotApplicable`.
+ *msg = Some(xcm);
+ }
+ })
+ }
+
+ fn deliver(ticket: Exporter::Ticket) -> Result<XcmHash, SendError> {
+ Exporter::deliver(ticket)
+ }
+
+ #[cfg(feature = "runtime-benchmarks")]
+ fn ensure_successful_delivery(_: Option<Location>) {}
+}
+
pub trait ExporterFor {
/// Return the locally-routable bridge (if any) capable of forwarding `message` to the
/// `remote_location` on the remote `network`, together with the payment which is required.
@@ -703,9 +755,9 @@ mod tests {
let local_dest: Location = (Parent, Parachain(5678)).into();
assert!(ensure_is_remote(UniversalLocation::get(), local_dest.clone()).is_err());
- // UnpaidLocalExporter
+ // LocalExporter
ensure_validate_does_not_consume_dest_or_msg::<
- UnpaidLocalExporter<RoutableBridgeExporter, UniversalLocation>,
+ LocalExporter<RoutableBridgeExporter, UniversalLocation>,
>(local_dest.clone(), |result| assert_eq!(Err(NotApplicable), result));
// 2. check with not applicable from the inner router (using `NotApplicableBridgeSender`)
@@ -713,14 +765,14 @@ mod tests {
(Parent, Parent, DifferentRemote::get(), RemoteDestination::get()).into();
assert!(ensure_is_remote(UniversalLocation::get(), remote_dest.clone()).is_ok());
- // UnpaidLocalExporter
+ // LocalExporter
ensure_validate_does_not_consume_dest_or_msg::<
- UnpaidLocalExporter<NotApplicableBridgeExporter, UniversalLocation>,
+ LocalExporter<NotApplicableBridgeExporter, UniversalLocation>,
>(remote_dest.clone(), |result| assert_eq!(Err(NotApplicable), result));
// 3. Ok - deliver
// UnpaidRemoteExporter
- assert_ok!(send_xcm::<UnpaidLocalExporter<RoutableBridgeExporter, UniversalLocation>>(
+ assert_ok!(send_xcm::<LocalExporter<RoutableBridgeExporter, UniversalLocation>>(
remote_dest,
Xcm::default()
));
diff --git a/prdoc/pr_7126.prdoc b/prdoc/pr_7126.prdoc
new file mode 100644
index 0000000000000000000000000000000000000000..1a86af1b2d1da8ade29829a01f83753637e915dd
--- /dev/null
+++ b/prdoc/pr_7126.prdoc
@@ -0,0 +1,7 @@
+title: 'xcm: Fixes for `UnpaidLocalExporter`'
+doc:
+- audience: Runtime Dev
+ description: This PR deprecates `UnpaidLocalExporter` in favor of the new `LocalExporter`. First, the name is misleading, as it can be used in both paid and unpaid scenarios. Second, it contains a hard-coded channel 0, whereas `LocalExporter` uses the same algorithm as `xcm-exporter`.
+crates:
+- name: staging-xcm-builder
+ bump: minor