pallet-xcm: Deprecate execute and send in favor of execute_blob and send_blob (#3749)

`execute` and `send` try to decode the xcm in the parameters before
reaching the filter line.
The new extrinsics decode only after the filter line.
These should be used instead of the old ones.

## TODO
- [x] Tests
- [x] Generate weights
- [x] Deprecation issue ->
https://github.com/paritytech/polkadot-sdk/issues/3771
- [x] PRDoc
- [x] Handle error in pallet-contracts

This would make writing XCMs in PJS Apps more difficult, but here's the
fix for that: https://github.com/polkadot-js/apps/pull/10350.
Already deployed! https://polkadot.js.org/apps/#/utilities/xcm

Supersedes https://github.com/paritytech/polkadot-sdk/pull/1798/

---------

Co-authored-by: PG Herveou <pgherveou@gmail.com>
Co-authored-by: command-bot <>
Co-authored-by: Adrian Catangiu <adrian@parity.io>

polkadot/xcm/xcm-builder/src/controller.rs

@@ -21,6 +21,7 @@
 use frame_support::{
 	dispatch::{DispatchErrorWithPostInfo, WithPostDispatchInfo},
 	pallet_prelude::DispatchError,
+	parameter_types, BoundedVec,
 };
 use sp_std::boxed::Box;
 use xcm::prelude::*;
@@ -41,8 +42,12 @@ impl<T, Origin, RuntimeCall, Timeout> Controller<Origin, RuntimeCall, Timeout> f
 
 /// Weight functions needed for [`ExecuteController`].
 pub trait ExecuteControllerWeightInfo {
-	/// Weight for [`ExecuteController::execute`]
-	fn execute() -> Weight;
+	/// Weight for [`ExecuteController::execute_blob`]
+	fn execute_blob() -> Weight;
+}
+
+parameter_types! {
+	pub const MaxXcmEncodedSize: u32 = xcm::MAX_XCM_ENCODED_SIZE;
 }
 
 /// Execute an XCM locally, for a given origin.
@@ -61,19 +66,19 @@ pub trait ExecuteController<Origin, RuntimeCall> {
 	/// # Parameters
 	///
 	/// - `origin`: the origin of the call.
-	/// - `message`: the XCM program to be executed.
+	/// - `msg`: the encoded XCM to be executed, should be decodable as a [`VersionedXcm`]
 	/// - `max_weight`: the maximum weight that can be consumed by the execution.
-	fn execute(
+	fn execute_blob(
 		origin: Origin,
-		message: Box<VersionedXcm<RuntimeCall>>,
+		message: BoundedVec<u8, MaxXcmEncodedSize>,
 		max_weight: Weight,
 	) -> Result<Weight, DispatchErrorWithPostInfo>;
 }
 
 /// Weight functions needed for [`SendController`].
 pub trait SendControllerWeightInfo {
-	/// Weight for [`SendController::send`]
-	fn send() -> Weight;
+	/// Weight for [`SendController::send_blob`]
+	fn send_blob() -> Weight;
 }
 
 /// Send an XCM from a given origin.
@@ -93,11 +98,11 @@ pub trait SendController<Origin> {
 	///
 	/// - `origin`: the origin of the call.
 	/// - `dest`: the destination of the message.
-	/// - `msg`: the XCM to be sent.
-	fn send(
+	/// - `msg`: the encoded XCM to be sent, should be decodable as a [`VersionedXcm`]
+	fn send_blob(
 		origin: Origin,
 		dest: Box<VersionedLocation>,
-		message: Box<VersionedXcm<()>>,
+		message: BoundedVec<u8, MaxXcmEncodedSize>,
 	) -> Result<XcmHash, DispatchError>;
 }
 
@@ -137,35 +142,35 @@ pub trait QueryController<Origin, Timeout>: QueryHandler {
 
 impl<Origin, RuntimeCall> ExecuteController<Origin, RuntimeCall> for () {
 	type WeightInfo = ();
-	fn execute(
+	fn execute_blob(
 		_origin: Origin,
-		_message: Box<VersionedXcm<RuntimeCall>>,
+		_message: BoundedVec<u8, MaxXcmEncodedSize>,
 		_max_weight: Weight,
 	) -> Result<Weight, DispatchErrorWithPostInfo> {
-		Err(DispatchError::Other("ExecuteController::execute not implemented")
+		Err(DispatchError::Other("ExecuteController::execute_blob not implemented")
 			.with_weight(Weight::zero()))
 	}
 }
 
 impl ExecuteControllerWeightInfo for () {
-	fn execute() -> Weight {
+	fn execute_blob() -> Weight {
 		Weight::zero()
 	}
 }
 
 impl<Origin> SendController<Origin> for () {
 	type WeightInfo = ();
-	fn send(
+	fn send_blob(
 		_origin: Origin,
 		_dest: Box<VersionedLocation>,
-		_message: Box<VersionedXcm<()>>,
+		_message: BoundedVec<u8, MaxXcmEncodedSize>,
 	) -> Result<XcmHash, DispatchError> {
 		Ok(Default::default())
 	}
 }
 
 impl SendControllerWeightInfo for () {
-	fn send() -> Weight {
+	fn send_blob() -> Weight {
 		Weight::zero()
 	}
 }

polkadot/xcm/xcm-builder/src/lib.rs

@@ -43,7 +43,7 @@ pub use barriers::{
 
 mod controller;
 pub use controller::{
-	Controller, ExecuteController, ExecuteControllerWeightInfo, QueryController,
+	Controller, ExecuteController, ExecuteControllerWeightInfo, MaxXcmEncodedSize, QueryController,
 	QueryControllerWeightInfo, QueryHandler, SendController, SendControllerWeightInfo,
 };