Assets pallet: Don't allow set_min_balance when sufficient

frame/assets/src/lib.rs

@@ -1540,10 +1540,15 @@ pub mod pallet {
 			ensure!(origin == details.owner, Error::<T, I>::NoPermission);
 
 			let old_min_balance = details.min_balance;
-			// Ensure that either the new min_balance is less than old min_balance or there aren't
-			// any accounts holding the asset.
+			let is_sufficient = details.is_sufficient;
+			// Ensure that either the new min_balance is less than old
+			// min_balance or there aren't any accounts holding the asset.
+			//
+			// If the asset is marked as sufficient we will only allow the owner
+			// to set the min_balance if the count of accounts holding the assets
+			// is zero.
 			ensure!(
-				min_balance < old_min_balance || details.accounts == 0,
+				(!is_sufficient && min_balance < old_min_balance) || details.accounts == 0,
 				Error::<T, I>::NoPermission
 			);
 

frame/assets/src/tests.rs

@@ -1098,23 +1098,62 @@ fn set_min_balance_should_work() {
 		Balances::make_free_balance_be(&1, 10);
 		assert_ok!(Assets::create(RuntimeOrigin::signed(1), id, 1, 30));
 
-		assert_ok!(Assets::mint(RuntimeOrigin::signed(1), id, 1, 50));
-		// won't execute because there is an asset holder.
+		assert_ok!(Assets::mint(RuntimeOrigin::signed(1), id, 1, 100));
+		// Won't execute because there is an asset holder.
 		assert_noop!(
 			Assets::set_min_balance(RuntimeOrigin::signed(1), id, 50),
 			Error::<Test>::NoPermission
 		);
 
-		// will execute because the new value of min_balance is less than the
-		// old value. 10 < 30
-		assert_ok!(Assets::mint(RuntimeOrigin::signed(1), id, 1, 10));
+		// Force asset status to make this a sufficient asset.
+		assert_ok!(Assets::force_asset_status(
+			RuntimeOrigin::root(),
+			id,
+			1,
+			1,
+			1,
+			1,
+			30,
+			true,
+			false
+		));
 
-		assert_ok!(Assets::burn(RuntimeOrigin::signed(1), id, 1, 50));
+		// Won't execute because there is an account holding the asset and the asset is marked as
+		// sufficient.
 		assert_noop!(
-			Assets::set_min_balance(RuntimeOrigin::signed(2), id, 50),
+			Assets::set_min_balance(RuntimeOrigin::signed(1), id, 10),
 			Error::<Test>::NoPermission
 		);
 
+		assert_ok!(Assets::burn(RuntimeOrigin::signed(1), id, 1, 100));
+
+		// Works because there are no asset holders.
+		assert_ok!(Assets::set_min_balance(RuntimeOrigin::signed(1), id, 60));
+		assert_eq!(Asset::<Test>::get(id).unwrap().min_balance, 60);
+
+		// Make the asset not sufficient.
+		assert_ok!(Assets::force_asset_status(
+			RuntimeOrigin::root(),
+			id,
+			1,
+			1,
+			1,
+			1,
+			60,
+			false,
+			false
+		));
+
+		// We mint the asset again.
+		assert_ok!(Assets::mint(RuntimeOrigin::signed(1), id, 1, 100));
+
+		// Will execute because the new value of min_balance is less than the
+		// old value. 10 < 30
+		assert_ok!(Assets::set_min_balance(RuntimeOrigin::signed(1), id, 10));
+		assert_eq!(Asset::<Test>::get(id).unwrap().min_balance, 10);
+
+		assert_ok!(Assets::burn(RuntimeOrigin::signed(1), id, 1, 100));
+
 		assert_ok!(Assets::set_min_balance(RuntimeOrigin::signed(1), id, 50));
 		assert_eq!(Asset::<Test>::get(id).unwrap().min_balance, 50);
 	});