pallet-uniques: decrement total_deposit when clearing collection metadata (#3976)

Decrements `total_deposit` when collection metadata is cleared in
`pallet-nfts` and `pallet-uniques`.

substrate/frame/uniques/src/lib.rs

@@ -1399,7 +1399,7 @@ pub mod pallet {
 				.map(|_| None)
 				.or_else(|origin| ensure_signed(origin).map(Some))?;
 
-			let details =
+			let mut details =
 				Collection::<T, I>::get(&collection).ok_or(Error::<T, I>::UnknownCollection)?;
 			if let Some(check_owner) = &maybe_check_owner {
 				ensure!(check_owner == &details.owner, Error::<T, I>::NoPermission);
@@ -1411,6 +1411,8 @@ pub mod pallet {
 
 				let deposit = metadata.take().ok_or(Error::<T, I>::UnknownCollection)?.deposit;
 				T::Currency::unreserve(&details.owner, deposit);
+				details.total_deposit.saturating_reduce(deposit);
+				Collection::<T, I>::insert(&collection, details);
 				Self::deposit_event(Event::CollectionMetadataCleared { collection });
 				Ok(())
 			})

substrate/frame/uniques/src/tests.rs

@@ -1062,3 +1062,41 @@ fn buy_item_should_work() {
 		}
 	});
 }
+
+#[test]
+fn clear_collection_metadata_works() {
+	new_test_ext().execute_with(|| {
+		// Start with an account with 100 balance, 10 of which are reserved
+		Balances::make_free_balance_be(&1, 100);
+		Balances::reserve(&1, 10).unwrap();
+
+		// Create a Unique which increases total_deposit by 2
+		assert_ok!(Uniques::create(RuntimeOrigin::signed(1), 0, 123));
+		assert_eq!(Collection::<Test>::get(0).unwrap().total_deposit, 2);
+		assert_eq!(Balances::reserved_balance(&1), 12);
+
+		// Set collection metadata which increases total_deposit by 10
+		assert_ok!(Uniques::set_collection_metadata(
+			RuntimeOrigin::signed(1),
+			0,
+			bvec![0, 0, 0, 0, 0, 0, 0, 0, 0],
+			false
+		));
+		assert_eq!(Collection::<Test>::get(0).unwrap().total_deposit, 12);
+		assert_eq!(Balances::reserved_balance(&1), 22);
+
+		// Clearing collection metadata reduces total_deposit by the expected amount
+		assert_ok!(Uniques::clear_collection_metadata(RuntimeOrigin::signed(1), 0));
+		assert_eq!(Collection::<Test>::get(0).unwrap().total_deposit, 2);
+		assert_eq!(Balances::reserved_balance(&1), 12);
+
+		// Destroying the collection removes it from storage
+		assert_ok!(Uniques::destroy(
+			RuntimeOrigin::signed(1),
+			0,
+			DestroyWitness { items: 0, item_metadatas: 0, attributes: 0 }
+		));
+		assert_eq!(Collection::<Test>::get(0), None);
+		assert_eq!(Balances::reserved_balance(&1), 10);
+	});
+}