fix: wrap award_course_certificate.delay in transaction.on_commit

COURSE_CERT_CHANGED fires synchronously during GeneratedCertificate.save(),
which runs inside the generate_certificate Celery task. The .delay() call
was enqueuing award_course_certificate before the DB transaction committed,
so the task raced ahead and hit eligible_certificates.get() DoesNotExist —
exiting silently with no retry, and never posting the course cert to
Credentials.

Wrapping in transaction.on_commit() guarantees the cert row is committed
before the task is enqueued.

Fixes: EDLYPRODUCT-5411

Author: Waleed-Mujahid

openedx/core/djangoapps/programs/signals.py

@@ -4,6 +4,7 @@
 
 import logging
 
+from django.db import transaction
 from django.dispatch import receiver
 
 from openedx.core.djangoapps.content.course_overviews.signals import COURSE_PACING_CHANGED
@@ -86,7 +87,7 @@ def handle_course_cert_changed(sender, user, course_key, mode, status, **kwargs)
     # import here, because signal is registered at startup, but items in tasks are not yet able to be loaded
     from openedx.core.djangoapps.programs.tasks import award_course_certificate
 
-    award_course_certificate.delay(user.username, str(course_key))
+    transaction.on_commit(lambda: award_course_certificate.delay(user.username, str(course_key)))
 
 
 @receiver(COURSE_CERT_REVOKED)

openedx/core/djangoapps/programs/tests/test_signals.py

@@ -142,7 +142,8 @@ def test_credentials_disabled(self, mock_is_learner_issuance_enabled, mock_task)
         assert mock_is_learner_issuance_enabled.call_count == 1
         assert mock_task.call_count == 0
 
-    def test_credentials_enabled(self, mock_is_learner_issuance_enabled, mock_task):
+    @mock.patch("django.db.transaction.on_commit", side_effect=lambda f: f())
+    def test_credentials_enabled(self, mock_on_commit, mock_is_learner_issuance_enabled, mock_task):
         """
         Ensures that the receiver function invokes the expected celery task
         when the credentials API configuration is enabled.
@@ -152,23 +153,28 @@ def test_credentials_enabled(self, mock_is_learner_issuance_enabled, mock_task):
         handle_course_cert_changed(**self.signal_kwargs)
 
         assert mock_is_learner_issuance_enabled.call_count == 1
+        assert mock_on_commit.call_count == 1
         assert mock_task.call_count == 1
         assert mock_task.call_args[0] == (TEST_USERNAME, str(TEST_COURSE_KEY))
 
-    def test_records_enabled(self, mock_is_learner_issuance_enabled, mock_task):
+    @mock.patch("django.db.transaction.on_commit", side_effect=lambda f: f())
+    def test_records_enabled(self, mock_on_commit, mock_is_learner_issuance_enabled, mock_task):
         mock_is_learner_issuance_enabled.return_value = True
 
         site_config = SiteConfigurationFactory.create(site_values={"course_org_filter": ["edX"]})
 
-        # Correctly sent
+        # Correctly sent (scheduled via transaction.on_commit)
         handle_course_cert_changed(**self.signal_kwargs)
+        assert mock_on_commit.called
         assert mock_task.called
+        mock_on_commit.reset_mock()
         mock_task.reset_mock()
 
         # Correctly not sent
         site_config.site_values["ENABLE_LEARNER_RECORDS"] = False
         site_config.save()
         handle_course_cert_changed(**self.signal_kwargs)
+        assert not mock_on_commit.called
         assert not mock_task.called