[Rococo<>Westend bridge] Allow any asset over the lane between the tw…

…o Asset Hubs (paritytech#4888)

On Westend Asset Hub, we allow Rococo Asset Hub to act as reserve for
any asset native to the Rococo or Ethereum ecosystems (practically
providing Westend access to Ethereum assets through double bridging:
W<>R<>Eth).

On Rococo Asset Hub, we allow Westend Asset Hub to act as reserve for
any asset native to the Westend ecosystem. We also allow Ethereum
contracts to act as reserves for the foreign assets identified by the
same respective contracts locations.

- [x] add emulated tests for various assets (native, trust-based,
foreign/bridged) going AHR -> AHW,
- [x] add equivalent tests for the other direction AHW -> AHR.

This PR is a prerequisite to doing the same for Polkadot<>Kusama bridge.

cumulus/parachains/integration-tests/emulated/chains/parachains/assets/asset-hub-rococo/src/genesis.rs

@@ -21,7 +21,7 @@ use sp_core::{sr25519, storage::Storage};
 use emulated_integration_tests_common::{
 	accounts, build_genesis_storage, collators, get_account_id_from_seed,
 	PenpalSiblingSovereignAccount, PenpalTeleportableAssetLocation, RESERVABLE_ASSET_ID,
-	SAFE_XCM_VERSION,
+	SAFE_XCM_VERSION, USDT_ID,
 };
 use parachains_common::{AccountId, Balance};
 
@@ -68,7 +68,10 @@ pub fn genesis() -> Storage {
 			..Default::default()
 		},
 		assets: asset_hub_rococo_runtime::AssetsConfig {
-			assets: vec![(RESERVABLE_ASSET_ID, AssetHubRococoAssetOwner::get(), true, ED)],
+			assets: vec![
+				(RESERVABLE_ASSET_ID, AssetHubRococoAssetOwner::get(), true, ED),
+				(USDT_ID, AssetHubRococoAssetOwner::get(), true, ED),
+			],
 			..Default::default()
 		},
 		foreign_assets: asset_hub_rococo_runtime::ForeignAssetsConfig {

cumulus/parachains/integration-tests/emulated/common/src/lib.rs

@@ -51,11 +51,14 @@ pub const SAFE_XCM_VERSION: u32 = xcm::prelude::XCM_VERSION;
 
 type AccountPublic = <MultiSignature as Verify>::Signer;
 
-// This asset is added to AH as Asset and reserved transfer between Parachain and AH
+// (trust-backed) Asset registered on AH and reserve-transferred between Parachain and AH
 pub const RESERVABLE_ASSET_ID: u32 = 1;
-// This asset is added to AH as ForeignAsset and teleported between Penpal and AH
+// ForeignAsset registered on AH and teleported between Penpal and AH
 pub const TELEPORTABLE_ASSET_ID: u32 = 2;
 
+// USDT registered on AH as (trust-backed) Asset and reserve-transferred between Parachain and AH
+pub const USDT_ID: u32 = 1984;
+
 pub const PENPAL_ID: u32 = 2000;
 pub const ASSETS_PALLET_ID: u8 = 50;
 

cumulus/parachains/integration-tests/emulated/tests/assets/asset-hub-rococo/src/tests/treasury.rs

@@ -20,7 +20,7 @@ use frame_support::{
 	sp_runtime::traits::Dispatchable,
 	traits::{
 		fungible::Inspect,
-		fungibles::{Create, Inspect as FungiblesInspect, Mutate},
+		fungibles::{Inspect as FungiblesInspect, Mutate},
 	},
 };
 use parachains_common::AccountId;
@@ -163,7 +163,7 @@ fn spend_roc_on_asset_hub() {
 #[test]
 fn create_and_claim_treasury_spend_in_usdt() {
 	const ASSET_ID: u32 = 1984;
-	const SPEND_AMOUNT: u128 = 1_000_000;
+	const SPEND_AMOUNT: u128 = 10_000_000;
 	// treasury location from a sibling parachain.
 	let treasury_location: Location = Location::new(1, PalletInstance(18));
 	// treasury account on a sibling parachain.
@@ -190,13 +190,7 @@ fn create_and_claim_treasury_spend_in_usdt() {
 	AssetHubRococo::execute_with(|| {
 		type Assets = <AssetHubRococo as AssetHubRococoPallet>::Assets;
 
-		// create an asset class and mint some assets to the treasury account.
-		assert_ok!(<Assets as Create<_>>::create(
-			ASSET_ID,
-			treasury_account.clone(),
-			true,
-			SPEND_AMOUNT / 2
-		));
+		// USDT created at genesis, mint some assets to the treasury account.
 		assert_ok!(<Assets as Mutate<_>>::mint_into(ASSET_ID, &treasury_account, SPEND_AMOUNT * 4));
 		// beneficiary has zero balance.
 		assert_eq!(<Assets as FungiblesInspect<_>>::balance(ASSET_ID, &alice,), 0u128,);

cumulus/parachains/integration-tests/emulated/tests/bridges/bridge-hub-rococo/src/lib.rs

@@ -35,11 +35,13 @@ mod imports {
 		xcm_emulator::{
 			assert_expected_events, bx, Chain, Parachain as Para, RelayChain as Relay, TestExt,
 		},
+		ASSETS_PALLET_ID, USDT_ID,
 	};
 	pub use parachains_common::AccountId;
 	pub use rococo_westend_system_emulated_network::{
 		asset_hub_rococo_emulated_chain::{
-			genesis::ED as ASSET_HUB_ROCOCO_ED, AssetHubRococoParaPallet as AssetHubRococoPallet,
+			genesis::{AssetHubRococoAssetOwner, ED as ASSET_HUB_ROCOCO_ED},
+			AssetHubRococoParaPallet as AssetHubRococoPallet,
 		},
 		asset_hub_westend_emulated_chain::{
 			genesis::ED as ASSET_HUB_WESTEND_ED, AssetHubWestendParaPallet as AssetHubWestendPallet,