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removes side-effects from tryOverpayment

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This commit is contained in:
Vito
2025-12-05 13:31:16 +01:00
parent edc4db7534
commit cb69f06ea2
3 changed files with 86 additions and 112 deletions
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36
src/test/app/LendingHelpers_test.cpp
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@@ -668,23 +668,14 @@ class LendingHelpers_test : public beast::unit_test::suite
std::cout << loanProperites.loanState.interestOutstanding() std::cout << loanProperites.loanState.interestOutstanding()
<< std::endl; << std::endl;
Number totalValueOutstanding =
loanProperites.loanState.valueOutstanding;
Number principalOutstanding =
loanProperites.loanState.principalOutstanding;
Number managementFeeOutstanding =
loanProperites.loanState.managementFeeDue;
Number periodicPayment = loanProperites.periodicPayment; Number periodicPayment = loanProperites.periodicPayment;
auto const ret = tryOverpayment( auto const ret = tryOverpayment(
asset, asset,
loanScale, loanScale,
overpaymentComponents, overpaymentComponents,
totalValueOutstanding, loanProperites.loanState,
principalOutstanding,
managementFeeOutstanding,
periodicPayment, periodicPayment,
paymentInterval,
periodicRate, periodicRate,
paymentsRemaining, paymentsRemaining,
managementFeeRate, managementFeeRate,
@@ -692,50 +683,45 @@ class LendingHelpers_test : public beast::unit_test::suite
BEAST_EXPECT(ret); BEAST_EXPECT(ret);
auto const& actualPaymentParts = *ret; auto const& [actualPaymentParts, newLoanProperties] = *ret;
auto const newState = newLoanProperties.loanState;
BEAST_EXPECTS( BEAST_EXPECTS(
actualPaymentParts.valueChange == actualPaymentParts.valueChange ==
((totalValueOutstanding - principalOutstanding - newState.interestDue - loanProperites.loanState.interestDue,
managementFeeOutstanding)) -
loanProperites.loanState.interestDue,
" valueChange mismatch: expected " + " valueChange mismatch: expected " +
to_string( to_string(
(totalValueOutstanding - principalOutstanding - newState.interestDue -
managementFeeOutstanding) -
loanProperites.loanState.interestDue) + loanProperites.loanState.interestDue) +
", got " + to_string(actualPaymentParts.valueChange)); ", got " + to_string(actualPaymentParts.valueChange));
BEAST_EXPECTS( BEAST_EXPECTS(
actualPaymentParts.feePaid == actualPaymentParts.feePaid ==
loanProperites.loanState.managementFeeDue - loanProperites.loanState.managementFeeDue -
managementFeeOutstanding, newState.managementFeeDue,
" feePaid mismatch: expected " + " feePaid mismatch: expected " +
to_string( to_string(
loanProperites.loanState.managementFeeDue - loanProperites.loanState.managementFeeDue -
managementFeeOutstanding) + newState.managementFeeDue) +
", got " + to_string(actualPaymentParts.feePaid)); ", got " + to_string(actualPaymentParts.feePaid));
BEAST_EXPECTS( BEAST_EXPECTS(
actualPaymentParts.principalPaid == actualPaymentParts.principalPaid ==
loanProperites.loanState.principalOutstanding - loanProperites.loanState.principalOutstanding -
principalOutstanding, newState.principalOutstanding,
" principalPaid mismatch: expected " + " principalPaid mismatch: expected " +
to_string( to_string(
loanProperites.loanState.principalOutstanding - loanProperites.loanState.principalOutstanding -
principalOutstanding) + newState.principalOutstanding) +
", got " + to_string(actualPaymentParts.principalPaid)); ", got " + to_string(actualPaymentParts.principalPaid));
BEAST_EXPECTS( BEAST_EXPECTS(
actualPaymentParts.interestPaid == actualPaymentParts.interestPaid ==
loanProperites.loanState.interestDue - loanProperites.loanState.interestDue - newState.interestDue,
(totalValueOutstanding - principalOutstanding -
managementFeeOutstanding),
" interestPaid mismatch: expected " + " interestPaid mismatch: expected " +
to_string( to_string(
loanProperites.loanState.interestDue - loanProperites.loanState.interestDue -
(totalValueOutstanding - principalOutstanding - newState.interestDue) +
managementFeeOutstanding)) +
", got " + to_string(actualPaymentParts.interestPaid)); ", got " + to_string(actualPaymentParts.interestPaid));
} }

9
src/xrpld/app/misc/LendingHelpers.h
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@@ -361,16 +361,13 @@ struct LoanStateDeltas
nonNegative(); nonNegative();
}; };
Expected<LoanPaymentParts, TER> Expected<std::pair<LoanPaymentParts, LoanProperties>, TER>
tryOverpayment( tryOverpayment(
Asset const& asset, Asset const& asset,
std::int32_t loanScale, std::int32_t loanScale,
ExtendedPaymentComponents const& overpaymentComponents, ExtendedPaymentComponents const& overpaymentComponents,
Number& totalValueOutstanding, LoanState const& roundedLoanState,
Number& principalOutstanding, Number const& periodicPayment,
Number& managementFeeOutstanding,
Number& periodicPayment,
std::uint32_t paymentInterval,
Number const& periodicRate, Number const& periodicRate,
std::uint32_t paymentRemaining, std::uint32_t paymentRemaining,
TenthBips16 const managementFeeRate, TenthBips16 const managementFeeRate,

153
src/xrpld/app/misc/detail/LendingHelpers.cpp
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@@ -2,6 +2,8 @@
// DO NOT REMOVE forces header file include to sort first // DO NOT REMOVE forces header file include to sort first
#include <xrpld/app/tx/detail/VaultCreate.h> #include <xrpld/app/tx/detail/VaultCreate.h>
#include <utility>
namespace ripple { namespace ripple {
bool bool
@@ -382,16 +384,13 @@ doPayment(
* The function preserves accumulated rounding errors across the re-amortization * The function preserves accumulated rounding errors across the re-amortization
* to ensure the loan state remains consistent with its payment history. * to ensure the loan state remains consistent with its payment history.
*/ */
Expected<LoanPaymentParts, TER> Expected<std::pair<LoanPaymentParts, LoanProperties>, TER>
tryOverpayment( tryOverpayment(
Asset const& asset, Asset const& asset,
std::int32_t loanScale, std::int32_t loanScale,
ExtendedPaymentComponents const& overpaymentComponents, ExtendedPaymentComponents const& overpaymentComponents,
Number& totalValueOutstanding, LoanState const& roundedOldState,
Number& principalOutstanding, Number const& periodicPayment,
Number& managementFeeOutstanding,
Number& periodicPayment,
std::uint32_t paymentInterval,
Number const& periodicRate, Number const& periodicRate,
std::uint32_t paymentRemaining, std::uint32_t paymentRemaining,
TenthBips16 const managementFeeRate, TenthBips16 const managementFeeRate,
@@ -401,15 +400,11 @@ tryOverpayment(
auto const raw = computeRawLoanState( auto const raw = computeRawLoanState(
periodicPayment, periodicRate, paymentRemaining, managementFeeRate); periodicPayment, periodicRate, paymentRemaining, managementFeeRate);
// Get the actual loan state (with accumulated rounding from past payments)
auto const rounded = constructLoanState(
totalValueOutstanding, principalOutstanding, managementFeeOutstanding);
// Calculate the accumulated rounding errors. These need to be preserved // Calculate the accumulated rounding errors. These need to be preserved
// across the re-amortization to maintain consistency with the loan's // across the re-amortization to maintain consistency with the loan's
// payment history. Without preserving these errors, the loan could end // payment history. Without preserving these errors, the loan could end
// up with a different total value than what the borrower has actually paid. // up with a different total value than what the borrower has actually paid.
auto const errors = rounded - raw; auto const errors = roundedOldState - raw;
// Compute the new principal by applying the overpayment to the raw // Compute the new principal by applying the overpayment to the raw
// (theoretical) principal. Use max with 0 to ensure we never go negative. // (theoretical) principal. Use max with 0 to ensure we never go negative.
@@ -450,37 +445,35 @@ tryOverpayment(
// rounding errors. This ensures the loan's tracked state remains // rounding errors. This ensures the loan's tracked state remains
// consistent with its payment history. // consistent with its payment history.
principalOutstanding = std::clamp( auto const principalOutstanding = std::clamp(
roundToAsset( roundToAsset(
asset, newRaw.principalOutstanding, loanScale, Number::upward), asset, newRaw.principalOutstanding, loanScale, Number::upward),
numZero, numZero,
rounded.principalOutstanding); roundedOldState.principalOutstanding);
totalValueOutstanding = std::clamp( auto const totalValueOutstanding = std::clamp(
roundToAsset( roundToAsset(
asset, asset,
principalOutstanding + newRaw.interestOutstanding(), principalOutstanding + newRaw.interestOutstanding(),
loanScale, loanScale,
Number::upward), Number::upward),
numZero, numZero,
rounded.valueOutstanding); roundedOldState.valueOutstanding);
managementFeeOutstanding = std::clamp( auto const managementFeeOutstanding = std::clamp(
roundToAsset(asset, newRaw.managementFeeDue, loanScale), roundToAsset(asset, newRaw.managementFeeDue, loanScale),
numZero, numZero,
rounded.managementFeeDue); roundedOldState.managementFeeDue);
auto const newRounded = constructLoanState( auto const roundedNewState = constructLoanState(
totalValueOutstanding, principalOutstanding, managementFeeOutstanding); totalValueOutstanding, principalOutstanding, managementFeeOutstanding);
// Update newLoanProperties so that checkLoanGuards can make an accurate // Update newLoanProperties so that checkLoanGuards can make an accurate
// evaluation. // evaluation.
newLoanProperties.loanState.valueOutstanding = newRounded.valueOutstanding; newLoanProperties.loanState = roundedNewState;
JLOG(j.debug()) << "new rounded value: " << newRounded.valueOutstanding JLOG(j.debug()) << "new rounded value: " << roundedNewState.valueOutstanding
<< ", principal: " << newRounded.principalOutstanding << ", principal: " << roundedNewState.principalOutstanding
<< ", interest gross: " << newRounded.interestOutstanding(); << ", interest gross: "
<< roundedNewState.interestOutstanding();
// Update the periodic payment to reflect the re-amortized schedule
periodicPayment = newLoanProperties.periodicPayment;
// check that the loan is still valid // check that the loan is still valid
if (auto const ter = checkLoanGuards( if (auto const ter = checkLoanGuards(
@@ -490,7 +483,7 @@ tryOverpayment(
// small interest amounts, that may have already been paid // small interest amounts, that may have already been paid
// off. Check what's still outstanding. This should // off. Check what's still outstanding. This should
// guarantee that the interest checks pass. // guarantee that the interest checks pass.
newRounded.interestOutstanding() != beast::zero, roundedNewState.interestOutstanding() != beast::zero,
paymentRemaining, paymentRemaining,
newLoanProperties, newLoanProperties,
j)) j))
@@ -520,19 +513,16 @@ tryOverpayment(
// LCOV_EXCL_STOP // LCOV_EXCL_STOP
} }
auto const deltas = rounded - newRounded; auto const deltas = roundedOldState - roundedNewState;
// The change in loan management fee is equal to the change between the old // The change in loan management fee is equal to the change between the old
// and the new outstanding management fees // and the new outstanding management fees
XRPL_ASSERT_PARTS( XRPL_ASSERT_PARTS(
deltas.managementFee == deltas.managementFee ==
rounded.managementFeeDue - managementFeeOutstanding, roundedOldState.managementFeeDue - managementFeeOutstanding,
"ripple::detail::tryOverpayment", "ripple::detail::tryOverpayment",
"no fee change"); "no fee change");
auto const hypotheticalValueOutstanding =
rounded.valueOutstanding - deltas.principal;
// Calculate how the loan's value changed due to the overpayment. // Calculate how the loan's value changed due to the overpayment.
// This should be negative (value decreased) or zero. A principal // This should be negative (value decreased) or zero. A principal
// overpayment should never increase the loan's value. // overpayment should never increase the loan's value.
@@ -543,21 +533,28 @@ tryOverpayment(
"the loan. Ignore the overpayment"; "the loan. Ignore the overpayment";
return Unexpected(tesSUCCESS); return Unexpected(tesSUCCESS);
} }
return LoanPaymentParts{
// Principal paid is the reduction in principal outstanding return std::make_pair(
.principalPaid = deltas.principal, LoanPaymentParts{
// Interest paid is the reduction in interest due // Principal paid is the reduction in principal outstanding
.interestPaid = .principalPaid = deltas.principal,
deltas.interest + overpaymentComponents.untrackedInterest, // Interest paid is the reduction in interest due
// Value change includes both the reduction from paying down principal .interestPaid =
// (negative) and any untracked interest penalties (positive, e.g., if deltas.interest + overpaymentComponents.untrackedInterest,
// the overpayment itself incurs a fee) // Value change includes both the reduction from paying down
.valueChange = // principal
valueChange + overpaymentComponents.trackedInterestPart(), // (negative) and any untracked interest penalties (positive, e.g.,
// Fee paid includes both the reduction in tracked management fees and // if
// any untracked fees on the overpayment itself // the overpayment itself incurs a fee)
.feePaid = deltas.managementFee + .valueChange =
overpaymentComponents.untrackedManagementFee}; valueChange + overpaymentComponents.trackedInterestPart(),
// Fee paid includes both the reduction in tracked management fees
// and
// any untracked fees on the overpayment itself
.feePaid = deltas.managementFee +
overpaymentComponents.untrackedManagementFee,
},
newLoanProperties);
} }
/* Validates and applies an overpayment to the loan state. /* Validates and applies an overpayment to the loan state.
@@ -581,20 +578,16 @@ doOverpayment(
NumberProxy& principalOutstandingProxy, NumberProxy& principalOutstandingProxy,
NumberProxy& managementFeeOutstandingProxy, NumberProxy& managementFeeOutstandingProxy,
NumberProxy& periodicPaymentProxy, NumberProxy& periodicPaymentProxy,
std::uint32_t const paymentInterval,
Number const& periodicRate, Number const& periodicRate,
std::uint32_t const paymentRemaining, std::uint32_t const paymentRemaining,
TenthBips16 const managementFeeRate, TenthBips16 const managementFeeRate,
beast::Journal j) beast::Journal j)
{ {
// Create temporary copies of the loan state that can be safely modified auto const loanState = constructLoanState(
// and discarded if the overpayment doesn't work out. This prevents totalValueOutstandingProxy,
// corrupting the actual ledger data if validation fails. principalOutstandingProxy,
Number totalValueOutstanding = totalValueOutstandingProxy; managementFeeOutstandingProxy);
Number principalOutstanding = principalOutstandingProxy; auto const periodicPayment = periodicPaymentProxy;
Number managementFeeOutstanding = managementFeeOutstandingProxy;
Number periodicPayment = periodicPaymentProxy;
JLOG(j.debug()) JLOG(j.debug())
<< "overpayment components:" << "overpayment components:"
<< ", totalValue before: " << *totalValueOutstandingProxy << ", totalValue before: " << *totalValueOutstandingProxy
@@ -613,11 +606,8 @@ doOverpayment(
asset, asset,
loanScale, loanScale,
overpaymentComponents, overpaymentComponents,
totalValueOutstanding, loanState,
principalOutstanding,
managementFeeOutstanding,
periodicPayment, periodicPayment,
paymentInterval,
periodicRate, periodicRate,
paymentRemaining, paymentRemaining,
managementFeeRate, managementFeeRate,
@@ -625,18 +615,19 @@ doOverpayment(
if (!ret) if (!ret)
return Unexpected(ret.error()); return Unexpected(ret.error());
auto const& loanPaymentParts = *ret; auto const& [loanPaymentParts, newLoanProperties] = *ret;
auto const newRoundedLoanState = newLoanProperties.loanState;
// Safety check: the principal must have decreased. If it didn't (or // Safety check: the principal must have decreased. If it didn't (or
// increased!), something went wrong in the calculation and we should // increased!), something went wrong in the calculation and we should
// reject the overpayment. // reject the overpayment.
if (principalOutstandingProxy <= principalOutstanding) if (principalOutstandingProxy <= newRoundedLoanState.principalOutstanding)
{ {
// LCOV_EXCL_START // LCOV_EXCL_START
JLOG(j.warn()) << "Overpayment not allowed: principal " JLOG(j.warn()) << "Overpayment not allowed: principal "
<< "outstanding did not decrease. Before: " << "outstanding did not decrease. Before: "
<< *principalOutstandingProxy << *principalOutstandingProxy << ". After: "
<< ". After: " << principalOutstanding; << newRoundedLoanState.principalOutstanding;
return Unexpected(tesSUCCESS); return Unexpected(tesSUCCESS);
// LCOV_EXCL_STOP // LCOV_EXCL_STOP
} }
@@ -647,28 +638,29 @@ doOverpayment(
XRPL_ASSERT_PARTS( XRPL_ASSERT_PARTS(
overpaymentComponents.trackedPrincipalDelta == overpaymentComponents.trackedPrincipalDelta ==
principalOutstandingProxy - principalOutstanding, principalOutstandingProxy -
newRoundedLoanState.principalOutstanding,
"ripple::detail::doOverpayment", "ripple::detail::doOverpayment",
"principal change agrees"); "principal change agrees");
// I'm not 100% sure the following asserts are correct. If in doubt, and // I'm not 100% sure the following asserts are correct. If in doubt, and
// everything else works, remove any that cause trouble. // everything else works, remove any that cause trouble.
JLOG(j.debug()) << "valueChange: " << loanPaymentParts.valueChange JLOG(j.debug())
<< ", totalValue before: " << *totalValueOutstandingProxy << "valueChange: " << loanPaymentParts.valueChange
<< ", totalValue after: " << totalValueOutstanding << ", totalValue before: " << *totalValueOutstandingProxy
<< ", totalValue delta: " << ", totalValue after: " << newRoundedLoanState.valueOutstanding
<< (totalValueOutstandingProxy - totalValueOutstanding) << ", totalValue delta: "
<< ", principalDelta: " << (totalValueOutstandingProxy - newRoundedLoanState.valueOutstanding)
<< overpaymentComponents.trackedPrincipalDelta << ", principalDelta: " << overpaymentComponents.trackedPrincipalDelta
<< ", principalPaid: " << loanPaymentParts.principalPaid << ", principalPaid: " << loanPaymentParts.principalPaid
<< ", Computed difference: " << ", Computed difference: "
<< overpaymentComponents.trackedPrincipalDelta - << overpaymentComponents.trackedPrincipalDelta -
(totalValueOutstandingProxy - totalValueOutstanding); (totalValueOutstandingProxy - newRoundedLoanState.valueOutstanding);
XRPL_ASSERT_PARTS( XRPL_ASSERT_PARTS(
loanPaymentParts.valueChange == loanPaymentParts.valueChange ==
totalValueOutstanding - newRoundedLoanState.valueOutstanding -
(totalValueOutstandingProxy - (totalValueOutstandingProxy -
overpaymentComponents.trackedPrincipalDelta) + overpaymentComponents.trackedPrincipalDelta) +
overpaymentComponents.trackedInterestPart(), overpaymentComponents.trackedInterestPart(),
@@ -683,10 +675,10 @@ doOverpayment(
// All validations passed, so update the proxy objects (which will // All validations passed, so update the proxy objects (which will
// modify the actual Loan ledger object) // modify the actual Loan ledger object)
totalValueOutstandingProxy = totalValueOutstanding; totalValueOutstandingProxy = newRoundedLoanState.valueOutstanding;
principalOutstandingProxy = principalOutstanding; principalOutstandingProxy = newRoundedLoanState.principalOutstanding;
managementFeeOutstandingProxy = managementFeeOutstanding; managementFeeOutstandingProxy = newRoundedLoanState.managementFeeDue;
periodicPaymentProxy = periodicPayment; periodicPaymentProxy = newLoanProperties.periodicPayment;
return loanPaymentParts; return loanPaymentParts;
} }
@@ -1955,7 +1947,6 @@ loanMakePayment(
principalOutstandingProxy, principalOutstandingProxy,
managementFeeOutstandingProxy, managementFeeOutstandingProxy,
periodicPaymentProxy, periodicPaymentProxy,
paymentInterval,
periodicRate, periodicRate,
paymentRemainingProxy, paymentRemainingProxy,
managementFeeRate, managementFeeRate,