Add CallbackHandle to pallet-assets (#12307)

* Add CallbackHandle to pallet-assets

* Address review comments

* Add use for sp_io::storage

* Rebase & review comments

* Fix UT

Co-authored-by: Hoon Kim <mail@hoonkim.me>

substrate/bin/node/runtime/src/lib.rs

@@ -1478,6 +1478,7 @@ impl pallet_assets::Config for Runtime {
 	type StringLimit = StringLimit;
 	type Freezer = ();
 	type Extra = ();
+	type CallbackHandle = ();
 	type WeightInfo = pallet_assets::weights::SubstrateWeight<Runtime>;
 	type RemoveItemsLimit = ConstU32<1000>;
 	#[cfg(feature = "runtime-benchmarks")]

substrate/frame/assets/src/functions.rs

@@ -664,7 +664,8 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 				status: AssetStatus::Live,
 			},
 		);
-		Self::deposit_event(Event::ForceCreated { asset_id: id, owner });
+		Self::deposit_event(Event::ForceCreated { asset_id: id, owner: owner.clone() });
+		T::CallbackHandle::created(&id, &owner);
 		Ok(())
 	}
 
@@ -754,6 +755,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 					approvals_destroyed: removed_approvals as u32,
 					approvals_remaining: details.approvals as u32,
 				});
+				T::CallbackHandle::destroyed(&id);
 				Ok(())
 			})?;
 		Ok(removed_approvals)

substrate/frame/assets/src/lib.rs

@@ -116,6 +116,11 @@
 //!
 //! Please refer to the [`Pallet`] struct for details on publicly available functions.
 //!
+//! ### Callbacks
+//!
+//! Using `CallbackHandle` associated type, user can configure custom callback functions which are
+//! executed when new asset is created or an existing asset is destroyed.
+//!
 //! ## Related Modules
 //!
 //! * [`System`](../frame_system/index.html)
@@ -171,6 +176,18 @@ pub use weights::WeightInfo;
 
 type AccountIdLookupOf<T> = <<T as frame_system::Config>::Lookup as StaticLookup>::Source;
 
+/// Trait with callbacks that are executed after successfull asset creation or destruction.
+pub trait AssetsCallback<AssetId, AccountId> {
+	/// Indicates that asset with `id` was successfully created by the `owner`
+	fn created(_id: &AssetId, _owner: &AccountId) {}
+
+	/// Indicates that asset with `id` has just been destroyed
+	fn destroyed(_id: &AssetId) {}
+}
+
+/// Empty implementation in case no callbacks are required.
+impl<AssetId, AccountId> AssetsCallback<AssetId, AccountId> for () {}
+
 #[frame_support::pallet]
 pub mod pallet {
 	use super::*;
@@ -283,6 +300,9 @@ pub mod pallet {
 		/// Additional data to be stored with an account's asset balance.
 		type Extra: Member + Parameter + Default + MaxEncodedLen;
 
+		/// Callback methods for asset state change (e.g. asset created or destroyed)
+		type CallbackHandle: AssetsCallback<Self::AssetId, Self::AccountId>;
+
 		/// Weight information for extrinsics in this pallet.
 		type WeightInfo: WeightInfo;
 
@@ -598,7 +618,14 @@ pub mod pallet {
 					status: AssetStatus::Live,
 				},
 			);
-			Self::deposit_event(Event::Created { asset_id: id, creator: owner, owner: admin });
+
+			Self::deposit_event(Event::Created {
+				asset_id: id,
+				creator: owner.clone(),
+				owner: admin,
+			});
+			T::CallbackHandle::created(&id, &owner);
+
 			Ok(())
 		}
 

substrate/frame/assets/src/mock.rs

@@ -20,11 +20,13 @@
 use super::*;
 use crate as pallet_assets;
 
+use codec::Encode;
 use frame_support::{
 	construct_runtime, parameter_types,
 	traits::{AsEnsureOriginWithArg, ConstU32, ConstU64, GenesisBuild},
 };
 use sp_core::H256;
+use sp_io::storage;
 use sp_runtime::{
 	testing::Header,
 	traits::{BlakeTwo256, IdentityLookup},
@@ -45,6 +47,9 @@ construct_runtime!(
 	}
 );
 
+type AccountId = u64;
+type AssetId = u32;
+
 impl frame_system::Config for Test {
 	type BaseCallFilter = frame_support::traits::Everything;
 	type BlockWeights = ();
@@ -55,7 +60,7 @@ impl frame_system::Config for Test {
 	type BlockNumber = u64;
 	type Hash = H256;
 	type Hashing = BlakeTwo256;
-	type AccountId = u64;
+	type AccountId = AccountId;
 	type Lookup = IdentityLookup<Self::AccountId>;
 	type Header = Header;
 	type RuntimeEvent = RuntimeEvent;
@@ -84,6 +89,17 @@ impl pallet_balances::Config for Test {
 	type ReserveIdentifier = [u8; 8];
 }
 
+pub struct AssetsCallbackHandle;
+impl AssetsCallback<AssetId, AccountId> for AssetsCallbackHandle {
+	fn created(_id: &AssetId, _owner: &AccountId) {
+		storage::set(b"asset_created", &().encode());
+	}
+
+	fn destroyed(_id: &AssetId) {
+		storage::set(b"asset_destroyed", &().encode());
+	}
+}
+
 impl Config for Test {
 	type RuntimeEvent = RuntimeEvent;
 	type Balance = u64;
@@ -100,6 +116,7 @@ impl Config for Test {
 	type StringLimit = ConstU32<50>;
 	type Freezer = TestFreezer;
 	type WeightInfo = ();
+	type CallbackHandle = AssetsCallbackHandle;
 	type Extra = ();
 	type RemoveItemsLimit = ConstU32<5>;
 	#[cfg(feature = "runtime-benchmarks")]

substrate/frame/assets/src/tests.rs

@@ -24,6 +24,7 @@ use frame_support::{
 	traits::{fungibles::InspectEnumerable, Currency},
 };
 use pallet_balances::Error as BalancesError;
+use sp_io::storage;
 use sp_runtime::{traits::ConvertInto, TokenError};
 
 fn asset_ids() -> Vec<u32> {
@@ -1194,3 +1195,32 @@ fn querying_roles_should_work() {
 		assert_eq!(Assets::freezer(0), Some(4));
 	});
 }
+
+#[test]
+fn normal_asset_create_and_destroy_callbacks_should_work() {
+	new_test_ext().execute_with(|| {
+		assert!(storage::get(b"asset_created").is_none());
+		assert!(storage::get(b"asset_destroyed").is_none());
+
+		Balances::make_free_balance_be(&1, 100);
+		assert_ok!(Assets::create(RuntimeOrigin::signed(1), 0, 1, 1));
+		assert!(storage::get(b"asset_created").is_some());
+		assert!(storage::get(b"asset_destroyed").is_none());
+
+		assert_ok!(Assets::start_destroy(RuntimeOrigin::signed(1), 0));
+		assert_ok!(Assets::destroy_accounts(RuntimeOrigin::signed(1), 0));
+		assert_ok!(Assets::destroy_approvals(RuntimeOrigin::signed(1), 0));
+		assert_ok!(Assets::finish_destroy(RuntimeOrigin::signed(1), 0));
+		assert!(storage::get(b"asset_destroyed").is_some());
+	});
+}
+
+#[test]
+fn root_asset_create_should_work() {
+	new_test_ext().execute_with(|| {
+		assert!(storage::get(b"asset_created").is_none());
+		assert_ok!(Assets::force_create(RuntimeOrigin::root(), 0, 1, true, 1));
+		assert!(storage::get(b"asset_created").is_some());
+		assert!(storage::get(b"asset_destroyed").is_none());
+	});
+}

substrate/frame/transaction-payment/asset-tx-payment/src/tests.rs

@@ -171,6 +171,7 @@ impl pallet_assets::Config for Runtime {
 	type StringLimit = ConstU32<20>;
 	type Freezer = ();
 	type Extra = ();
+	type CallbackHandle = ();
 	type WeightInfo = ();
 	type RemoveItemsLimit = ConstU32<1000>;
 	pallet_assets::runtime_benchmarks_enabled! {