merchant

commit 91729ce58f8579d7470c8c599a97c13dfbcc7b55
parent a2beb276c7230c189bef3e3c5e47e32054b22617
Author: Florian Dold <dold@taler.net>
Date:   Sun,  6 Sep 2026 12:41:06 +0200

payments: retain pending deposit responses after an exchange error

Wait for outstanding batch responses before returning an exchange error.
A cancelled request may already have deposited coins, so record
successful responses to preserve the refund path for an incomplete
payment.

Diffstat:
M
src/backend/taler-merchant-httpd_post-orders-ORDER_ID-pay.c
 | 
59
+++++++++++++++++++++++++++++++++++++++++++++++++++++------

1 file changed, 53 insertions(+), 6 deletions(-)
diff --git a/src/backend/taler-merchant-httpd_post-orders-ORDER_ID-pay.c b/src/backend/taler-merchant-httpd_post-orders-ORDER_ID-pay.c
@@ -925,6 +925,9 @@ resume_pay_with_response (struct PayContext *pc,
                           unsigned int response_code,
                           struct MHD_Response *response)
 {
+  if ( (NULL != pc->response) &&
+       (pc->response != response) )
+    MHD_destroy_response (pc->response);
   pc->response_code = response_code;
   pc->response = response;
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
@@ -1307,6 +1310,35 @@ do_batch_deposits (struct ExchangeGroup *eg);
 
 
 /**
+ * Retain the first batch error until outstanding deposits have been recorded.
+ * Cancelling another exchange's request cannot undo its accepted deposit.
+ *
+ * @param pc payment context
+ * @param response_code HTTP status to return
+ * @param response response to retain
+ */
+static void
+defer_batch_deposit_error (struct PayContext *pc,
+                          unsigned int response_code,
+                          struct MHD_Response *response)
+{
+  if (NULL == pc->response)
+  {
+    pc->response = response;
+    pc->response_code = response_code;
+  }
+  else
+  {
+    MHD_destroy_response (response);
+  }
+  if (0 == pc->batch_deposits.pending_at_eg)
+    resume_pay_with_response (pc,
+                              pc->response_code,
+                              pc->response);
+}
+
+
+/**
  * Callback to handle a batch deposit permission's response.
  *
  * @param cls a `struct ExchangeGroup`
@@ -1361,8 +1393,15 @@ batch_deposit_cb (
     }
     if (0 == pc->batch_deposits.pending_at_eg)
     {
-      pc->phase = PP_COMPUTE_MONEY_POTS;
-      pay_resume (pc);
+      if (NULL != pc->response)
+        resume_pay_with_response (pc,
+                                  pc->response_code,
+                                  pc->response);
+      else
+      {
+        pc->phase = PP_COMPUTE_MONEY_POTS;
+        pay_resume (pc);
+      }
     }
     return;
   default:
@@ -1383,7 +1422,7 @@ batch_deposit_cb (
     if (5 == dr->hr.http_status / 100)
     {
       /* internal server error at exchange */
-      resume_pay_with_response (pc,
+      defer_batch_deposit_error (pc,
                                 MHD_HTTP_BAD_GATEWAY,
                                 TALER_MHD_MAKE_JSON_PACK (
                                   TALER_JSON_pack_ec (
@@ -1394,7 +1433,7 @@ batch_deposit_cb (
     if (NULL == dr->hr.reply)
     {
       /* We can't do anything meaningful here, the exchange did something wrong */
-      resume_pay_with_response (
+      defer_batch_deposit_error (
         pc,
         MHD_HTTP_BAD_GATEWAY,
         TALER_MHD_MAKE_JSON_PACK (
@@ -1408,7 +1447,7 @@ batch_deposit_cb (
        error was being generated */
     if (TALER_EC_EXCHANGE_GENERIC_INSUFFICIENT_FUNDS == dr->hr.ec)
     {
-      resume_pay_with_response (
+      defer_batch_deposit_error (
         pc,
         MHD_HTTP_CONFLICT,
         TALER_MHD_MAKE_JSON_PACK (
@@ -1419,7 +1458,7 @@ batch_deposit_cb (
                                    eg->exchange_url)));
       return;
     }
-    resume_pay_with_response (
+    defer_batch_deposit_error (
       pc,
       MHD_HTTP_BAD_GATEWAY,
       TALER_MHD_MAKE_JSON_PACK (
@@ -1439,6 +1478,14 @@ do_batch_deposits (struct ExchangeGroup *eg)
   struct PayContext *pc = eg->pc;
   struct TMH_HandlerContext *hc = pc->hc;
   unsigned int group_size = 0;
+  if (NULL != pc->response)
+  {
+    if (0 == pc->batch_deposits.pending_at_eg)
+      resume_pay_with_response (pc,
+                                pc->response_code,
+                                pc->response);
+    return;
+  }
   /* Initiate /batch-deposit operation for all coins of
      the current exchange (!) */