103.md: Remaining collateral used by ERC721Pool is missed in Auctions…

… take and bucketTake return structures

src/libraries/external/Auctions.sol

@@ -514,7 +514,8 @@ library Auctions {
  result_.poolDebt,
  result_.newLup,
  result_.t0DebtInAuctionChange,
- result_.settledAuction
+ result_.settledAuction,
+ result_.remainingCollateral
  ) = _takeLoan(
  auctions_,
  buckets_,
@@ -580,7 +581,8 @@ library Auctions {
  result_.poolDebt,
  result_.newLup,
  result_.t0DebtInAuctionChange,
- result_.settledAuction
+ result_.settledAuction,
+ result_.remainingCollateral
  ) = _takeLoan(
  auctions_,
  buckets_,
@@ -989,6 +991,7 @@ library Auctions {
  * @return newLup_ The new LUP of pool (after debt is repaid).
  * @return t0DebtInAuctionChange_ The overall debt in auction change (remaining borrower debt if auction settled, repaid debt otherwise).
  * @return settledAuction_ True if auction is settled by the take action.
+ * @return remainingCollateral_ Borrower collateral remaining after take action. (NFT take: collateral to be rebalanced in case of NFT settlement)
  */
  function _takeLoan(
  AuctionsState storage auctions_,
@@ -1003,7 +1006,8 @@ library Auctions {
  uint256 poolDebt_,
  uint256 newLup_,
  uint256 t0DebtInAuctionChange_,
- bool settledAuction_
+ bool settledAuction_,
+ uint256 remainingCollateral_
  ) {
 
  TakeLoanLocalVars memory vars;
@@ -1031,14 +1035,16 @@ library Auctions {
  t0DebtInAuctionChange_ = borrower_.t0Debt;
 
  // settle auction and update borrower's collateral with value after settlement
- borrower_.collateral = _settleAuction(
+ remainingCollateral_ = _settleAuction(
  auctions_,
  buckets_,
  deposits_,
  borrowerAddress_,
  borrower_.collateral,
  poolState_.poolType
  );
+
+ borrower_.collateral = remainingCollateral_;
  } else {
  // the overall debt in auction change is the amount of partially repaid debt
  t0DebtInAuctionChange_ = t0RepaidDebt_;

tests/forge/ERC721Pool/ERC721PoolLiquidationsTake.t.sol

@@ -776,6 +776,15 @@ contract ERC721PoolLiquidationsTakeTest is ERC721HelperContract {
  borrowerCollateralization: 1 * 1e18
  });
 
+ // borrower should be able to remove collateral in the pool
+ _repayDebtNoLupCheck({
+ from: _borrower,
+ borrower: _borrower,
+ amountToRepay: 0,
+ amountRepaid: 0,
+ collateralToPull: 1
+ });
+
  vm.revertTo(snapshot);
 
  // borrower repays part of debt, but not enough to exit from auction