fix: Use last zombie trove first in a redemption sequence #426
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RickGriff
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Sep 19, 2024
| @@ -53,6 +53,8 @@ interface ITroveManager is ILiquityBase { | |||
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| function getCurrentICR(uint256 _troveId, uint256 _price) external view returns (uint256); | |||
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| function lastZombieTroveId() external view returns (uint256); | |||
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"last" here refers to the last Trove that was redeemed to below MIN_DEBT right?
| if (newDebt > 0) { | ||
| lastZombieTroveId = _singleRedemption.troveId; | ||
| } | ||
| } else if (newDebt == 0) { |
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OK, so newDebt == 0 implies this Trove was fully redeemed, therefore we unzombify it
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I wouldn’t say “unzombified”. It’s still zombie, but it doesn’t hold the pointer to be the first one in the next redemption sequence anymore.
| @@ -730,15 +745,27 @@ contract TroveManager is LiquityBase, ITroveManager, ITroveEvents { | |||
| uint256 remainingBold = _boldamount; | |||
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| SingleRedemptionValues memory singleRedemption; | |||
| singleRedemption.troveId = sortedTrovesCached.getLast(); | |||
| // Let’s check if there’s a pending zombie trove from previous redemption | |||
| if (lastZombieTroveId != 0) { | |||
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We can never have a valid troveId == 0, right?
| @@ -769,6 +796,7 @@ contract TroveManager is LiquityBase, ITroveManager, ITroveEvents { | |||
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| remainingBold -= singleRedemption.boldLot; | |||
| singleRedemption.troveId = nextUserToCheck; | |||
| singleRedemption.isZombieTrove = false; | |||
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We only need to do this if it was a zombieTrove. Though seems fine to just do it here at the end.
| @@ -1450,6 +1483,8 @@ contract TroveManager is LiquityBase, ITroveManager, ITroveEvents { | |||
| } else { | |||
| if (trove.status == Status.active) { | |||
| sortedTroves.remove(_troveId); | |||
| } else if (trove.status == Status.zombie && lastZombieTroveId == _troveId) { | |||
| lastZombieTroveId = 0; | |||
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Do we need this logic twice? Could we do it once at the end?
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Closes #425
Note: with this implementation, it can happen that a trove belonging to a batch, has both entire and recorded debt, due to the batch being updated (even the function
redeemCollateraldoes that as a preliminary step) but without a direct action on the trove, and the trove is still zombie and holds the pointer to the last zombie trove, so it gets redeemed first in the list.This seems like quite an edge case, and the user can easily prevent it by taking care of the trove before.