fix: email failure after payment no longer shows a 500 to interactive callers

_send_payslip_email caught email errors, queued a warning toast, then
re-raised unconditionally — but only batch_pay catches that re-raise.
The Pay button (process_payment) and the three Pay-Immediately paths in
add_adjustment called it bare, so an SMTP failure AFTER the payment
committed replaced the warning with a 500 error page (the 28 May 2026
incident behaviour — admin can't tell the payment saved, may pay twice).

Re-raise is now conditional on suppress_messages=True (the batch path,
which counts failures in its summary); interactive callers get the
warning toast as intended. Regression tests cover both sides.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/tests.py

@@ -3,7 +3,9 @@
 # determines, for each worker on a log, whether they were paid for it.
 
 import datetime
+import json
 from decimal import Decimal
+from unittest import mock
 
 from django.conf import settings
 from django.contrib.auth.models import User
@@ -3679,3 +3681,65 @@ class ManagerSalariedPayUITests(TestCase):
         # guard test).
         self.assertNotIn('Salary Details', body)
         self.assertNotIn('Salary Amount:', body)
+
+
+# =============================================================================
+# === AUDIT FIX #1 — EMAIL FAILURE AFTER PAYMENT MUST NOT 500 ===
+# Regression tests for the 28 May 2026 incident class: SMTP breaks, the
+# payment commits, and the admin must see a warning toast — NOT an error
+# page (which hides that the payment DID go through and invites a
+# dangerous second click of Pay).
+# =============================================================================
+
+class PaymentEmailFailureTests(TestCase):
+    """Email failure after a successful payment: warn the admin, never crash."""
+
+    def setUp(self):
+        self.admin = User.objects.create_user(
+            username='emailfail_admin', password='x', is_staff=True)
+        self.client.force_login(self.admin)
+        self.project = Project.objects.create(name='EF Project')
+        self.worker = Worker.objects.create(
+            name='EF Worker', id_number='EF-1', monthly_salary=Decimal('8000'))
+        log = WorkLog.objects.create(
+            date=datetime.date(2026, 6, 1), project=self.project,
+            supervisor=self.admin)
+        log.workers.add(self.worker)
+
+    def _broken_smtp(self):
+        # Simulate the 28 May 2026 state: every send() raises (bad creds /
+        # SMTP unreachable / empty DEFAULT_FROM_EMAIL).
+        return mock.patch(
+            'django.core.mail.EmailMultiAlternatives.send',
+            side_effect=Exception('SMTP down'))
+
+    def test_individual_payment_survives_email_failure(self):
+        with self._broken_smtp():
+            resp = self.client.post(
+                reverse('process_payment', args=[self.worker.id]), follow=True)
+        # The payment was saved...
+        self.assertEqual(
+            PayrollRecord.objects.filter(worker=self.worker).count(), 1)
+        # ...and the admin landed back on a normal page (not a 500)
+        self.assertEqual(resp.status_code, 200)
+        msgs = [str(m) for m in resp.context['messages']]
+        self.assertTrue(
+            any('email delivery failed' in m for m in msgs),
+            f'expected an email-failure warning toast, got: {msgs}')
+
+    def test_batch_pay_still_counts_email_failures(self):
+        # The batch path NEEDS the helper to re-raise internally so it can
+        # count failures — this guards the other side of the conditional.
+        with self._broken_smtp():
+            resp = self.client.post(
+                reverse('batch_pay'),
+                data=json.dumps({'workers': [{'worker_id': self.worker.id}]}),
+                content_type='application/json',
+                follow=True)
+        self.assertEqual(
+            PayrollRecord.objects.filter(worker=self.worker).count(), 1)
+        self.assertEqual(resp.status_code, 200)
+        msgs = [str(m) for m in resp.context['messages']]
+        self.assertTrue(
+            any('1 email(s) failed to send' in m for m in msgs),
+            f'expected batch summary to count the email failure, got: {msgs}')

core/views.py

@@ -3804,14 +3804,20 @@ def _send_payslip_email(request, worker, payroll_record, log_count, logs_amount,
                     f'Payslip emailed successfully.'
                 )
         except Exception as e:
-            # Payment is saved — just warn that email failed
-            if not suppress_messages:
-                messages.warning(
-                    request,
-                    f'Payment of R {total_amount:,.2f} processed for {worker.name}, '
-                    f'but email delivery failed: {str(e)}'
-                )
-            raise  # Re-raise so batch_pay can count failures
+            # Payment is saved — the email is the only thing that failed.
+            # Batch mode (suppress_messages=True) re-raises so batch_pay can
+            # count failures in its summary. Interactive callers (the Pay
+            # button, Pay-Immediately adjustments) get a warning toast
+            # instead — a raise here would show the admin a 500 page and
+            # hide the fact that the payment DID go through (the 28 May
+            # 2026 incident behaviour).
+            if suppress_messages:
+                raise  # batch_pay catches this and counts it
+            messages.warning(
+                request,
+                f'Payment of R {total_amount:,.2f} processed for {worker.name}, '
+                f'but email delivery failed: {str(e)}'
+            )
     else:
         # No SPARK_RECEIPT_EMAIL configured — just show success
         if not suppress_messages: