From 30e2650ff985a5bbc93e2f7374b2258e385dd990 Mon Sep 17 00:00:00 2001
From: Ed Hennis <ed@ripple.com>
Date: Wed, 22 Oct 2025 17:15:34 -0400
Subject: [PATCH] Use a loan scale of 0 for integral asset types

- Loan scale is completely irrelevant to integral types (XRP, MPT), and
  the field is "soeDEFAULT", so when set to 0, it won't be stored on
  ledger, saving a little bit of space.
---
 src/test/app/Loan_test.cpp          | 20 ++++++++++++++------
 src/xrpld/app/misc/LendingHelpers.h |  9 ++++++++-
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/src/test/app/Loan_test.cpp b/src/test/app/Loan_test.cpp
index 9fd0f8541a..45a076b2ed 100644
--- a/src/test/app/Loan_test.cpp
+++ b/src/test/app/Loan_test.cpp
@@ -404,7 +404,10 @@ class Loan_test : public beast::unit_test::suite
             BEAST_EXPECT(
                 state.principalOutstanding == broker.asset(1000).value());
             BEAST_EXPECT(
-                state.principalOutstanding.exponent() == state.loanScale);
+                state.loanScale ==
+                (broker.asset.integral()
+                     ? 0
+                     : state.principalOutstanding.exponent()));
             BEAST_EXPECT(state.paymentInterval == 600);
             BEAST_EXPECT(
                 state.totalValue ==
@@ -636,7 +639,9 @@ class Loan_test : public beast::unit_test::suite
             BEAST_EXPECT(
                 loan->at(sfNextPaymentDueDate) == startDate + interval);
             BEAST_EXPECT(loan->at(sfPaymentRemaining) == total);
-            BEAST_EXPECT(loan->at(sfLoanScale) == principalRequest.exponent());
+            BEAST_EXPECT(
+                loan->at(sfLoanScale) ==
+                (broker.asset.integral() ? 0 : principalRequest.exponent()));
             BEAST_EXPECT(loan->at(sfPrincipalOutstanding) == principalRequest);
         }
 
@@ -654,7 +659,7 @@ class Loan_test : public beast::unit_test::suite
             0,
             startDate + interval,
             total,
-            principalRequest.exponent(),
+            broker.asset.integral() ? 0 : principalRequest.exponent(),
             loanProperties.totalValueOutstanding,
             principalRequest,
             loanProperties.managementFeeOwedToBroker,
@@ -711,7 +716,7 @@ class Loan_test : public beast::unit_test::suite
             0,
             nextDueDate,
             total,
-            principalRequest.exponent(),
+            broker.asset.integral() ? 0 : principalRequest.exponent(),
             loanProperties.totalValueOutstanding,
             principalRequest,
             loanProperties.managementFeeOwedToBroker,
@@ -1196,7 +1201,10 @@ class Loan_test : public beast::unit_test::suite
                 BEAST_EXPECT(brokerSle))
             {
                 BEAST_EXPECT(
-                    state.loanScale == state.principalOutstanding.exponent());
+                    state.loanScale ==
+                    (broker.asset.integral()
+                         ? 0
+                         : state.principalOutstanding.exponent()));
                 auto const defaultAmount = roundToAsset(
                     broker.asset,
                     std::min(
@@ -2166,7 +2174,7 @@ class Loan_test : public beast::unit_test::suite
             BEAST_EXPECT(!loan.isMember(sfPreviousPaymentDate));
             BEAST_EXPECT(loan[sfPrincipalOutstanding] == "1000000000");
             BEAST_EXPECT(loan[sfTotalValueOutstanding] == "1000000000");
-            BEAST_EXPECT(loan[sfLoanScale] == -6);
+            BEAST_EXPECT(!loan.isMember(sfLoanScale));
             BEAST_EXPECT(
                 loan[sfStartDate].asUInt() ==
                 startDate.time_since_epoch().count());
diff --git a/src/xrpld/app/misc/LendingHelpers.h b/src/xrpld/app/misc/LendingHelpers.h
index b843bfc344..b63cdcb505 100644
--- a/src/xrpld/app/misc/LendingHelpers.h
+++ b/src/xrpld/app/misc/LendingHelpers.h
@@ -1158,7 +1158,7 @@ computeLoanProperties(
 
     auto const periodicPayment = detail::loanPeriodicPayment(
         principalOutstanding, periodicRate, paymentsRemaining);
-    Number const totalValueOutstanding = [&]() {
+    STAmount const totalValueOutstanding = [&]() {
         NumberRoundModeGuard mg(Number::to_nearest);
         // Use STAmount's internal rounding instead of roundToAsset, because
         // we're going to use this result to determine the scale for all the
@@ -1176,6 +1176,13 @@ computeLoanProperties(
     // biggest number involved (barring unusual parameters for late, full, or
     // over payments)
     auto const loanScale = totalValueOutstanding.exponent();
+    XRPL_ASSERT_PARTS(
+        totalValueOutstanding.integral() && loanScale == 0 ||
+            !totalValueOutstanding.integral() &&
+                loanScale ==
+                    static_cast<Number>(totalValueOutstanding).exponent(),
+        "ripple::computeLoanProperties",
+        "loanScale value fits expectations");
 
     // Since we just figured out the loan scale, we haven't been able to
     // validate that the principal fits in it, so to allow this function to