Allow Creation of Asset Accounts That Don't Exist Yet and Add Blocked Status

bin/node/runtime/src/lib.rs

@@ -1860,6 +1860,7 @@ type Migrations = (
 	pallet_nomination_pools::migration::v2::MigrateToV2<Runtime>,
 	pallet_alliance::migration::Migration<Runtime>,
 	pallet_contracts::Migration<Runtime>,
+	pallet_assets::migration::v2::MigrateToV2<Runtime>,
 );
 
 /// MMR helper types.

frame/assets/src/benchmarking.rs

@@ -277,6 +277,18 @@ benchmarks_instance_pallet! {
 		assert_last_event::<T, I>(Event::Frozen { asset_id: asset_id.into(), who: caller }.into());
 	}
 
+	freeze_creating {
+		let (asset_id, asset_owner, _asset_owner_lookup) = create_default_minted_asset::<T, I>(true, 100u32.into());
+		let target: T::AccountId = account("target", 1, SEED);
+		let target_lookup = T::Lookup::unlookup(target.clone());
+		assert_ne!(asset_owner, target);
+		T::Currency::make_free_balance_be(&asset_owner, DepositBalanceOf::<T, I>::max_value());
+		assert!(!Account::<T, I>::contains_key(asset_id.into(), &target));
+	}: _(SystemOrigin::Signed(asset_owner.clone()), asset_id, target_lookup)
+	verify {
+		assert_last_event::<T, I>(Event::Frozen { asset_id: asset_id.into(), who: target }.into());
+	}
+
 	thaw {
 		let (asset_id, caller, caller_lookup) = create_default_minted_asset::<T, I>(true, 100u32.into());
 		Assets::<T, I>::freeze(
@@ -482,5 +494,61 @@ benchmarks_instance_pallet! {
 		assert_last_event::<T, I>(Event::AssetMinBalanceChanged { asset_id: asset_id.into(), new_min_balance: 50u32.into() }.into());
 	}
 
+	touch {
+		let (asset_id, asset_owner, asset_owner_lookup) = create_default_asset::<T, I>(false);
+		let new_account: T::AccountId = account("newaccount", 1, SEED);
+		T::Currency::make_free_balance_be(&new_account, DepositBalanceOf::<T, I>::max_value());
+		assert_ne!(asset_owner, new_account);
+		assert!(!Account::<T, I>::contains_key(asset_id.into(), &new_account));
+	}: _(SystemOrigin::Signed(new_account.clone()), asset_id)
+	verify {
+		assert!(Account::<T, I>::contains_key(asset_id.into(), &new_account));
+	}
+
+	refund {
+		let (asset_id, asset_owner, asset_owner_lookup) = create_default_asset::<T, I>(false);
+		let new_account: T::AccountId = account("newaccount", 1, SEED);
+		T::Currency::make_free_balance_be(&new_account, DepositBalanceOf::<T, I>::max_value());
+		assert_ne!(asset_owner, new_account);
+		assert!(Assets::<T, I>::touch(
+			SystemOrigin::Signed(new_account.clone()).into(),
+			asset_id
+		).is_ok());
+		// `touch` should reserve some balance of the caller...
+		assert!(!T::Currency::reserved_balance(&new_account).is_zero());
+		// ...and also create an `Account` entry.
+		assert!(Account::<T, I>::contains_key(asset_id.into(), &new_account));
+	}: _(SystemOrigin::Signed(new_account.clone()), asset_id, true)
+	verify {
+		// `refund`ing should of course repatriate the reserve
+		assert!(T::Currency::reserved_balance(&new_account).is_zero());
+	}
+
+	refund_other {
+		let (asset_id, asset_owner, asset_owner_lookup) = create_default_asset::<T, I>(false);
+		let new_account: T::AccountId = account("newaccount", 1, SEED);
+		let new_account_lookup = T::Lookup::unlookup(new_account.clone());
+		T::Currency::make_free_balance_be(&asset_owner, DepositBalanceOf::<T, I>::max_value());
+		assert_ne!(asset_owner, new_account);
+		assert!(Assets::<T, I>::freeze_creating(
+			SystemOrigin::Signed(asset_owner.clone()).into(),
+			asset_id,
+			new_account_lookup.clone()
+		).is_ok());
+		// `freeze_creating` should reserve balance of the freezer
+		assert!(!T::Currency::reserved_balance(&asset_owner).is_zero());
+		assert!(Assets::<T, I>::thaw(
+			SystemOrigin::Signed(asset_owner.clone()).into(),
+			asset_id,
+			new_account_lookup.clone()
+		).is_ok());
+		// the account should still exist, just not be frozen
+		assert!(Account::<T, I>::contains_key(asset_id.into(), &new_account));
+	}: _(SystemOrigin::Signed(asset_owner.clone()), asset_id, new_account.clone(), true)
+	verify {
+		// this should repatriate the reserved balance of the freezer
+		assert!(T::Currency::reserved_balance(&asset_owner).is_zero());
+	}
+
 	impl_benchmark_test_suite!(Assets, crate::mock::new_test_ext(), crate::mock::Test)
 }

frame/assets/src/functions.rs

@@ -123,30 +123,39 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		amount: T::Balance,
 		increase_supply: bool,
 	) -> DepositConsequence {
+		use DepositConsequence::*;
 		let details = match Asset::<T, I>::get(id) {
 			Some(details) => details,
-			None => return DepositConsequence::UnknownAsset,
+			None => return UnknownAsset,
 		};
 		if increase_supply && details.supply.checked_add(&amount).is_none() {
-			return DepositConsequence::Overflow
+			return Overflow
+		}
+		// We don't allow freezing of accounts that don't already have an `(AssetId, AccountId)`
+		// entry. The account may have a zero balance provided by a deposit placed by `touch`ing the
+		// account. However, frozen accounts cannot receive more of the `AssetID`.
+		if let Some(a) = Account::<T, I>::get(id, who) {
+			if a.is_frozen {
+				return Frozen
+			}
 		}
 		if let Some(balance) = Self::maybe_balance(id, who) {
 			if balance.checked_add(&amount).is_none() {
-				return DepositConsequence::Overflow
+				return Overflow
 			}
 		} else {
 			if amount < details.min_balance {
-				return DepositConsequence::BelowMinimum
+				return BelowMinimum
 			}
 			if !details.is_sufficient && !frame_system::Pallet::<T>::can_inc_consumer(who) {
-				return DepositConsequence::CannotCreate
+				return CannotCreate
 			}
 			if details.is_sufficient && details.sufficients.checked_add(1).is_none() {
-				return DepositConsequence::Overflow
+				return Overflow
 			}
 		}
 
-		DepositConsequence::Success
+		Success
 	}
 
 	/// Return the consequence of a withdraw.
@@ -302,14 +311,18 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		Ok((credit, maybe_burn))
 	}
 
-	/// Creates a account for `who` to hold asset `id` with a zero balance and takes a deposit.
-	pub(super) fn do_touch(id: T::AssetId, who: T::AccountId) -> DispatchResult {
+	/// Creates an account for `who` to hold asset `id` with a zero balance and takes a deposit.
+	pub(super) fn do_touch(
+		id: T::AssetId,
+		who: &T::AccountId,
+		depositor: &T::AccountId,
+	) -> DispatchResult {
 		ensure!(!Account::<T, I>::contains_key(id, &who), Error::<T, I>::AlreadyExists);
 		let deposit = T::AssetAccountDeposit::get();
 		let mut details = Asset::<T, I>::get(&id).ok_or(Error::<T, I>::Unknown)?;
 		ensure!(details.status == AssetStatus::Live, Error::<T, I>::AssetNotLive);
 		let reason = Self::new_account(&who, &mut details, Some(deposit))?;
-		T::Currency::reserve(&who, deposit)?;
+		T::Currency::reserve(&depositor, deposit)?;
 		Asset::<T, I>::insert(&id, details);
 		Account::<T, I>::insert(
 			id,
@@ -318,26 +331,46 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 				balance: Zero::zero(),
 				is_frozen: false,
 				reason,
+				depositor: Some(depositor.clone()),
 				extra: T::Extra::default(),
 			},
 		);
 		Ok(())
 	}
 
 	/// Returns a deposit, destroying an asset-account.
-	pub(super) fn do_refund(id: T::AssetId, who: T::AccountId, allow_burn: bool) -> DispatchResult {
+	pub(super) fn do_refund(
+		caller: &T::AccountId,
+		id: T::AssetId,
+		who: &T::AccountId,
+		allow_burn: bool,
+	) -> DispatchResult {
 		let mut account = Account::<T, I>::get(id, &who).ok_or(Error::<T, I>::NoDeposit)?;
 		let deposit = account.reason.take_deposit().ok_or(Error::<T, I>::NoDeposit)?;
 		let mut details = Asset::<T, I>::get(&id).ok_or(Error::<T, I>::Unknown)?;
 		ensure!(details.status == AssetStatus::Live, Error::<T, I>::AssetNotLive);
 		ensure!(account.balance.is_zero() || allow_burn, Error::<T, I>::WouldBurn);
 		ensure!(!account.is_frozen, Error::<T, I>::Frozen);
 
-		T::Currency::unreserve(&who, deposit);
+		let mut refund_to: T::AccountId = who.clone();
+		if let Some(depositor) = account.depositor.take() {
+			// Only the account owner (`who`), the depositor, or the asset admin can remove an
+			// account. That is, a depositor cannot force another's account to exist with zero
+			// balance.
+			ensure!(
+				caller == &depositor || caller == who || caller == &details.admin,
+				Error::<T, I>::NoPermission
+			);
+			refund_to = depositor;
+		}
+		T::Currency::unreserve(&refund_to, deposit);
+		account.depositor = None;
 
 		if let Remove = Self::dead_account(&who, &mut details, &account.reason, false) {
 			Account::<T, I>::remove(id, &who);
 		} else {
+			// deposit has been refunded, need to update `Account`
+			Account::<T, I>::insert(id, &who, account);
 			debug_assert!(false, "refund did not result in dead account?!");
 		}
 		Asset::<T, I>::insert(&id, details);
@@ -408,6 +441,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 						*maybe_account = Some(AssetAccountOf::<T, I> {
 							balance: amount,
 							reason: Self::new_account(beneficiary, details, None)?,
+							depositor: None,
 							is_frozen: false,
 							extra: T::Extra::default(),
 						});
@@ -604,6 +638,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 							balance: credit,
 							is_frozen: false,
 							reason: Self::new_account(dest, details, None)?,
+							depositor: None,
 							extra: T::Extra::default(),
 						});
 					},
@@ -938,4 +973,32 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 			.filter_map(|id| Self::maybe_balance(id, account.clone()).map(|balance| (id, balance)))
 			.collect::<Vec<_>>()
 	}
+
+	/// Freeze an account `who`, preventing further reception or transfer of asset `id`.
+	pub(super) fn do_freeze(
+		check_freezer: T::AccountId,
+		id: T::AssetId,
+		who: T::AccountId,
+		create: bool,
+	) -> DispatchResult {
+		let d = Asset::<T, I>::get(id).ok_or(Error::<T, I>::Unknown)?;
+		ensure!(
+			d.status == AssetStatus::Live || d.status == AssetStatus::Frozen,
+			Error::<T, I>::AssetNotLive
+		);
+		ensure!(check_freezer == d.freezer, Error::<T, I>::NoPermission);
+
+		if create && Account::<T, I>::get(id, &who).is_none() {
+			// we create the account with zero balance, but the freezer must place a deposit
+			let _ = Self::do_touch(id, &who, &check_freezer)?;
+		}
+
+		Account::<T, I>::try_mutate(id, &who, |maybe_account| -> DispatchResult {
+			maybe_account.as_mut().ok_or(Error::<T, I>::NoAccount)?.is_frozen = true;
+			Ok(())
+		})?;
+
+		Self::deposit_event(Event::<T, I>::Frozen { asset_id: id, who });
+		Ok(())
+	}
 }