Rebalance Vote or Delegation in New Conviction Voting Pallet

[shawntabrizi]

I think we should make an extrinsic which allows any user to reduce or remove another users vote if their free balance falls below their vote balance. For example if a user get slashed, their vote amount will not get updated automatically, but such a call would provide a mechanism for the community to rebalance this.

Originally posted by @shawntabrizi in paritytech/substrate#10195 (comment)

[Doordashcon]

I don't quite understand the need to reduce another users vote, can't it just be removed if the target's free balance falls below their vote balance?

[shawntabrizi]

Removing it seems more extreme than reducing it. If we could remove users votes completely because they fall 1 unit lower than before, this could be used to censor people.

[Doordashcon]

cc @shawntabrizi Say a user has voted for multiple polls and he gets slashed as a nominator/validator while the polls are ongoing, falling 1 unit lower in balance of what the user was at before, doesn't that mean the rebalance extrinsic has to somehow collate all the polls the user have voted on and then reduce the tally of the votes of that user & delegations to that user across board equivocally by 1 unit?

[Doordashcon]

@georgesdib would you like to take over this issue?

[georgesdib]

cc @shawntabrizi Strange behaviour for the Voting pallet, not sure if it's intended. The below tests succeed, while I would not have expected them to, is this normal?

#[test]
fn voting_balance_gets_locked_across_polls() {
	new_test_ext().execute_with(|| {
		// Activate the 2 polls
		Polls::set(
			vec![(2, Ongoing(Tally::default(), 2)), (3, Ongoing(Tally::default(), 2))]
				.into_iter()
				.collect(),
		);
		assert_ok!(Voting::vote(Origin::signed(1), 3, aye(2, 5)));
		// 1 voted in poll 3, tally is good
		assert_eq!(tally(3), Tally::from_parts(10, 0, 2));
		// and usable balance is good
		assert_eq!(Balances::usable_balance(1), 8);
		assert_ok!(Voting::vote(Origin::signed(1), 2, aye(8, 5)));
		// 1 voted in poll 2, tally is good
		assert_eq!(tally(2), Tally::from_parts(40, 0, 8));
		// the tally is still there for poll 3, ie 1's vote still counts
		assert_eq!(tally(3), Tally::from_parts(10, 0, 2));
		// However, the original funds are not locked anymore (usable_balance should be 0)
		assert_eq!(Balances::usable_balance(1), 2);
	})
}

#[test]
fn voting_balance_gets_locked_across_polls_max_funds() {
	new_test_ext().execute_with(|| {
		// Activate the 2 polls
		Polls::set(
			vec![(2, Ongoing(Tally::default(), 2)), (3, Ongoing(Tally::default(), 2))]
				.into_iter()
				.collect(),
		);
		assert_ok!(Voting::vote(Origin::signed(1), 3, aye(8, 5)));
		// 1 voted in poll 3, tally is good
		assert_eq!(tally(3), Tally::from_parts(40, 0, 8));
		// and usable balance is good
		assert_eq!(Balances::usable_balance(1), 2);
		assert_ok!(Voting::vote(Origin::signed(1), 2, aye(2, 5)));
		// 1 voted in poll 2, tally is good
		assert_eq!(tally(2), Tally::from_parts(10, 0, 2));
		// the tally is still there for poll 3, ie 1's vote still counts
		assert_eq!(tally(3), Tally::from_parts(40, 0, 8));
		// However, it only locks the max of the 2 funds (ie instead of locking 2+8=10, it
		// locked max(2, 8) = 8)
		assert_eq!(Balances::usable_balance(1), 2);
	})
}