taler-typescript-core

commit 40678e819eb909d6856da8a3d07942c44ff1d33c
parent 57fe4ca6d3758fcc85fd579e0c558ff4c6b105de
Author: Florian Dold <florian@dold.me>
Date:   Mon, 22 Dec 2025 13:06:58 +0100

wallet-core: fix wrong estimate of peer-push-debit fees

The wallet lazily validates denominations. In the request for computing
the effective total cost of a P2P push payment, we did not properly
ensure that denominations which might be used in the refresh step are
validated. Thus wallet-core would sometimes over-estimate the fees by
assuming a 100 percent refresh fee due to missing validated
denominations for withdrawal.

Diffstat:
M
packages/taler-wallet-core/src/exchanges.ts
 | 
3
+++
M
packages/taler-wallet-core/src/pay-peer-common.ts
 | 
9
+++++++++
M
packages/taler-wallet-core/src/pay-peer-push-debit.ts
 | 
4
++++

3 files changed, 16 insertions(+), 0 deletions(-)
diff --git a/packages/taler-wallet-core/src/exchanges.ts b/packages/taler-wallet-core/src/exchanges.ts
@@ -1422,6 +1422,9 @@ export async function fetchFreshExchange(
     },
   );
 
+  // FIXME: We should only transition here when
+  // the update is forced or necessary!
+
   await wex.taskScheduler.ensureRunning();
 
   await startUpdateExchangeEntry(wex, baseUrl, {
diff --git a/packages/taler-wallet-core/src/pay-peer-common.ts b/packages/taler-wallet-core/src/pay-peer-common.ts
@@ -44,6 +44,7 @@ import {
 import { getTotalRefreshCost } from "./refresh.js";
 import { BalanceEffect, applyNotifyTransition } from "./transactions.js";
 import { WalletExecutionContext, getDenomInfo } from "./wallet.js";
+import { updateWithdrawalDenomsForExchange } from "./withdraw.js";
 
 /**
  * Get information about the coin selected for signatures.
@@ -121,6 +122,14 @@ export async function getTotalPeerPaymentCost(
   wex: WalletExecutionContext,
   pcs: SelectedProspectiveCoin[],
 ): Promise<AmountJson> {
+  // We first need to make sure we have already validated
+  // potential target denomination for the refresh.
+  // This must happen *before* we start the transaction.
+  if (pcs.length > 0) {
+    // P2P payments currently support only one exchange.
+    const exchangeBaseUrl = pcs[0].exchangeBaseUrl;
+    await updateWithdrawalDenomsForExchange(wex, exchangeBaseUrl);
+  }
   return wex.db.runReadOnlyTx(
     { storeNames: ["coins", "denominations"] },
     async (tx) => {
diff --git a/packages/taler-wallet-core/src/pay-peer-push-debit.ts b/packages/taler-wallet-core/src/pay-peer-push-debit.ts
@@ -81,6 +81,7 @@ import {
   timestampProtocolToDb,
 } from "./db.js";
 import {
+  fetchFreshExchange,
   getPreferredExchangeForCurrency,
   getScopeForAllExchanges,
 } from "./exchanges.js";
@@ -441,6 +442,9 @@ async function internalCheckPeerPushDebit(
       assertUnreachable(coinSelRes);
   }
   logger.trace(`selected peer coins (len=${coins.length})`);
+  // We might need to do a refresh later, so it's important
+  // that we have up-to-date info about the exchange.
+  await fetchFreshExchange(wex, coinSelRes.result.exchangeBaseUrl);
   const totalAmount = await getTotalPeerPaymentCost(wex, coins);
   logger.trace("computed total peer payment cost");
   return {