fix: ensure we are selecting the correct date for self-paced courses (#36465)

It is possible for self-paced courses to be configured with a display behavior of "END" even though this configuration option should be invalid. The fix to this problem is beyond the scope of this PR. However, we can ensure we are selecting the correct display date for the certificate with a little bit of defensive coding.

I've added a check to ensure that we only use the end date of the course when the course is instructor-paced and configured with a display behavior of "END".

Author: justinhynes

lms/djangoapps/certificates/api.py

@@ -880,7 +880,14 @@ def display_date_for_certificate(course, certificate):
 
     if _course_uses_available_date(course) and course.certificate_available_date < datetime.now(UTC):
         return course.certificate_available_date
-    elif course.certificates_display_behavior == CertificatesDisplayBehaviors.END and course.end:
+    # It is possible for a self-paced course run to end up configured with a display behavior of "END" even though it
+    # shouldn't be a valid option. We must check if the course is instructor-paced here to ensure that we are selecting
+    # the correct date to display.
+    elif (
+        not course.self_paced
+        and course.certificates_display_behavior == CertificatesDisplayBehaviors.END
+        and course.end
+    ):
         return course.end
     else:
         return certificate.modified_date

lms/djangoapps/certificates/tests/test_api.py

@@ -1141,6 +1141,7 @@ def test_display_date_for_certificate_cdb_early_no_info(self):
         certificate instance when the display behavior is set to EARLY_NO_INFO.
         """
         with configure_waffle_namespace(True):
+            self.course.self_paced = False
             self.course.certificates_display_behavior = CertificatesDisplayBehaviors.EARLY_NO_INFO
             assert display_date_for_certificate(self.course, self.certificate) == self.certificate.modified_date
 
@@ -1150,6 +1151,7 @@ def test_display_date_for_certificate_cdb_end_with_date(self):
         associated with the course when the display behavior is set to END_WITH_DATE.
         """
         with configure_waffle_namespace(True):
+            self.course.self_paced = False
             self.course.certificates_display_behavior = CertificatesDisplayBehaviors.END_WITH_DATE
             self.course.certificate_available_date = datetime(2017, 2, 1, tzinfo=pytz.UTC)
             assert display_date_for_certificate(self.course, self.certificate) == self.course.certificate_available_date
@@ -1160,6 +1162,7 @@ def test_display_date_for_certificate_cdb_end(self):
         when the display behavior is set to END.
         """
         with configure_waffle_namespace(True):
+            self.course.self_paced = False
             self.course.certificates_display_behavior = CertificatesDisplayBehaviors.END
             assert display_date_for_certificate(self.course, self.certificate) == self.course.end
 
@@ -1172,6 +1175,27 @@ def test_display_date_for_certificate_date_override(self):
             self.certificate.date_override = datetime(2016, 1, 1, tzinfo=pytz.UTC)
             assert display_date_for_certificate(self.course, self.certificate) == self.certificate.date_override.date
 
+    def test_display_date_for_self_paced_course_run(self):
+        """
+        Test to verify that the "earned date" displayed on a course certificate is the last modified date of a
+        certificate instance when the display behavior is set to EARLY_NO_INFO and the course run is self-paced.
+        """
+        with configure_waffle_namespace(True):
+            self.course.self_paced = True
+            self.course.certificates_display_behavior = CertificatesDisplayBehaviors.EARLY_NO_INFO
+            assert display_date_for_certificate(self.course, self.certificate) == self.certificate.modified_date
+
+    def test_display_date_for_self_paced_course_run_with_cdb_end(self):
+        """
+        Test for a bug fix and some defensive coding. It is possible for self-paced course runs to end up with a display
+        behavior of END. This test ensures that we select the correct issue date even when the course run's
+        configuration is unexpected.
+        """
+        with configure_waffle_namespace(True):
+            self.course.self_paced = True
+            self.course.certificates_display_behavior = CertificatesDisplayBehaviors.END
+            assert display_date_for_certificate(self.course, self.certificate) == self.certificate.modified_date
+
 
 @ddt.ddt
 class CertificatesMessagingTestCase(ModuleStoreTestCase):