taler-typescript-core

commit 66835ab57e8c1710532a3cb9f622b9077e902047
parent 732cf258e3fce3dfb2c5e323e4038a533b2d5788
Author: Florian Dold <dold@taler.net>
Date:   Mon, 20 Jul 2026 13:58:59 +0200

util: throw on subtraction of denormalized amounts

Diffstat:
M
packages/taler-util/src/amounts.test.ts
 | 
6
++++++
M
packages/taler-util/src/amounts.ts
 | 
4
+++-

2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/packages/taler-util/src/amounts.test.ts b/packages/taler-util/src/amounts.test.ts
@@ -57,6 +57,12 @@ test("amount subtraction (saturation)", (t) => {
   assert.ok(!res.saturated);
 });
 
+test("Amounts.sub throws instead of silently underflowing on a denormalized fraction", (t) => {
+  assert.throws(() =>
+    Amounts.sub(jAmt(10, 0, "EUR"), jAmt(2, 250000000, "EUR")),
+  );
+});
+
 test("amount comparison", (t) => {
   assert.strictEqual(Amounts.cmp(jAmt(1, 0, "EUR"), jAmt(1, 0, "EUR")), 0);
   assert.strictEqual(Amounts.cmp(jAmt(1, 1, "EUR"), jAmt(1, 0, "EUR")), 1);
diff --git a/packages/taler-util/src/amounts.ts b/packages/taler-util/src/amounts.ts
@@ -374,7 +374,9 @@ export class Amounts {
         value--;
         fraction += amountFractionalBase;
       }
-      console.assert(fraction >= bJ.fraction);
+      if (fraction < bJ.fraction) {
+        throw Error("assertion failed: fraction underflow in Amounts.sub");
+      }
       fraction -= bJ.fraction;
       if (value < bJ.value) {
         return { amount: { currency, value: 0, fraction: 0 }, saturated: true };