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🩹 market: mirror fixed repay rounding in position preview #10

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Merged
cruzdanilo merged 1 commit into from
May 12, 2026
Merged

🩹 market: mirror fixed repay rounding in position preview #10

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5 changes: 5 additions & 0 deletions .changeset/kind-walls-write.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@exactly/lib": patch
---

🩹 market: mirror fixed repay rounding in position preview
7 changes: 6 additions & 1 deletion src/market/fixedRepayPosition.ts
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Expand Up @@ -39,6 +39,11 @@ export default function fixedRepayPosition(
const r = mulDiv(netUnassignedEarnings, k, backupSupplied);
if (r >= WAD) return min(assets + netUnassignedEarnings, totalPosition);
const x = divWad(assets, WAD - r);
if (mulWad(k, x) <= backupSupplied && x <= totalPosition) return x;
const scaledPrincipal = mulDiv(x, principal, totalPosition);
const gross = mulDiv(unassignedEarnings, min(scaledPrincipal, backupSupplied), backupSupplied);
const pos = min(assets + gross - mulWad(gross, backupFeeRate), totalPosition);
const earned = mulDiv(unassignedEarnings, min(mulDiv(pos, principal, totalPosition), backupSupplied), backupSupplied);
const repay = pos - earned + mulWad(earned, backupFeeRate);
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cruzdanilo marked this conversation as resolved.
if (scaledPrincipal <= backupSupplied && x <= totalPosition) return pos - (repay > assets ? repay - assets : 0n);

@coderabbitai coderabbitai Bot May 12, 2026

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🧹 Nitpick | 🔵 Trivial | ⚡ Quick win

Consider documenting the return adjustment logic.

The expression pos - (repay > assets ? repay - assets : 0n) performs a non-trivial adjustment. When repay > assets, this effectively returns pos - repay + assets, which algebraically simplifies to a complex relationship between earned amounts, fees, and the backup fee rate. A brief inline comment explaining the business logic (e.g., "adjust position to account for repayment shortfall") would aid maintainability.

@chatgpt-codex-connector chatgpt-codex-connector Bot May 12, 2026

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P2 Badge Revalidate the corrected position

After this patch's one-shot subtraction, the returned position can still cost more than the caller's asset limit because lowering pos also lowers the earned-yield offset used by fixedRepayAssets. For example, with principal=7743n, fee=408n, borrowed=813061n, supplied=647081n, unassignedEarnings=298005n, backupFeeRate=450351310267204224n, lastAccrual=1n, maturity=1000, timestamp=1, and assets=119n, this branch returns 1900n, but fixedRepayAssets(..., 1900n, 1) is 120n. Please iterate/recompute until the forward calculation is <= assets rather than subtracting only the first observed excess.

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return min(assets + netUnassignedEarnings, totalPosition);
}