test xcm transact

[yrong]

cumulus:
4cdf87d

rococo:
yrong/polkadot@b70b0af

the core logic in parachain side is wrap a transact xcm to invoke test pallet function in relaychain as following:

cumulus/rococo-parachains/pallets/ping/src/lib.rs

Lines 135 to 171 in 4cdf87d

	log::info!(
	target: "ping",
	"Begin construct relay transact"
	);
	let some_value:u32 = 10;
	let call = RelayTemplatePalletCall::DoSomething(DoSomethingCall::Something(some_value)).encode();
	let msg = Xcm::Transact {
	origin_type: OriginKind::SovereignAccount,
	require_weight_at_most: 1_000,
	call:call.into(),
	};
	log::info!(
	target: "ping",
	"Relay transact {:?}",
	msg,
	);
	match T::XcmSender::send_xcm(MultiLocation::X1(Junction::Parent), msg){
	Ok(()) => {
	Self::deposit_event(Event::TestMsg(some_value));
	log::info!(
	target: "ping",
	"Relay transact sent success!"
	);
	},
	Err(e) => {
	Self::deposit_event(Event::ErrorSendingTest());
	log::error!(
	target: "ping",
	"Relay transact sent failed!"
	);
	}
	}
	}
	}

from parachain log we can see:

2021-05-16 16:01:48  [Parachain] Begin construct relay transact    
2021-05-16 16:01:48  [Parachain] Relay transact Transact { origin_type: Native, require_weight_at_most: 1000, call: [100, 0, 10, 0, 0, 0] }    
2021-05-16 16:01:48  [Parachain] Relay transact sent success!  

2021-05-16 16:01:50  [Relaychain] 💤 Idle (4 peers), best: #939 (0xdc19…668f), finalized #936 (0xee40…7ea9), ⬇ 0.9kiB/s ⬆ 3.4kiB/s    
2021-05-16 16:01:50  [Parachain] 💤 Idle (0 peers), best: #299 (0x91c2…12b2), finalized #297 (0xd553…92a3), ⬇ 0 ⬆ 0    

which demonstrate parachain is successfully registered to relay chain and transact are wrapped and sent successfully

the relay chain pallet will update storage and emit event as following:

https://github.com/yrong/polkadot/blob/b70b0af3f5d1226ae31bd3e5c3ced2ebfa105380/template/src/lib.rs#L79-L82

from relay chain event we can see:

which demonstrate relaychain finish the dispatch call successfully

[yrong]

some notes:

• pallet index and call index in transact call should be consistent with value in relay chain runtime
  

  cumulus/rococo-parachains/pallets/ping/src/lib.rs

  Lines 31 to 41 in 4cdf87d

  	#[derive(Encode, Decode)]
  	pub enum RelayTemplatePalletCall {
  	#[codec(index = 100)] // the index should match the position of the module in `construct_runtime!`
  	DoSomething(DoSomethingCall),
  	}
  	#[derive(Encode, Decode)]
  	pub enum DoSomethingCall {
  	#[codec(index = 0)] // the index should match the position of the dispatchable in the target pallet
  	Something(u32),
  	}

  
  https://github.com/yrong/polkadot/blob/b70b0af3f5d1226ae31bd3e5c3ced2ebfa105380/runtime/rococo/src/lib.rs#L259

• origin_type in transact should satisfy the call requirement in relay chain

  cumulus/rococo-parachains/pallets/ping/src/lib.rs

  Line 143 in 4cdf87d

  origin_type: OriginKind::SovereignAccount,

  
  https://github.com/yrong/polkadot/blob/b70b0af3f5d1226ae31bd3e5c3ced2ebfa105380/template/src/lib.rs#L76

• disable barrier weight check temporarily
  https://github.com/yrong/polkadot/blob/b70b0af3f5d1226ae31bd3e5c3ced2ebfa105380/xcm/xcm-executor/src/lib.rs#L119-L121

[yrong]

challenge:

• currently the transact call is async and not safe guaranted, execution in parachain side will always be successful even if the call is failed in relay chain side. there are some issues tracking and seems still some infrastruct code lacking

paritytech#206
polkadot-fellows/xcm-format#22