From f36673aff933c31c31fdc5d419672bea4a530a4c Mon Sep 17 00:00:00 2001
From: Emma Green <emma.green.software@gmail.com>
Date: Tue, 26 Feb 2019 10:56:36 -0500
Subject: [PATCH] fix course program cache

---
 .../management/commands/cache_programs.py     | 13 +++++------
 .../djangoapps/catalog/tests/test_utils.py    | 22 +++++++++++++++++++
 openedx/core/djangoapps/catalog/utils.py      |  4 +++-
 3 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/openedx/core/djangoapps/catalog/management/commands/cache_programs.py b/openedx/core/djangoapps/catalog/management/commands/cache_programs.py
index 35b2416bd9..5388ccc855 100644
--- a/openedx/core/djangoapps/catalog/management/commands/cache_programs.py
+++ b/openedx/core/djangoapps/catalog/management/commands/cache_programs.py
@@ -1,3 +1,5 @@
+""""Management command to add program information to the cache."""
+from collections import defaultdict
 import logging
 import sys
 
@@ -211,15 +213,12 @@ class Command(BaseCommand):
         in the cache not just the course runs in a program. Therefore, a cache miss would be different from a
         course not in a program.
         """
-        course_runs = {}
+        course_runs = defaultdict(list)
         failure = False
 
-        for program_uuid, program in programs.items():
+        for program in programs.values():
             for course in program['courses']:
                 for course_run in course['course_runs']:
-                    course_run_key = course_run['key']
-                    if course_run_key in course_runs:
-                        course_runs[course_run_key] += program_uuid
-                    else:
-                        course_runs[course_run_key] = [program_uuid]
+                    course_run_cache_key = COURSE_PROGRAMS_CACHE_KEY_TPL.format(course_run_id=course_run['key'])
+                    course_runs[course_run_cache_key].append(program['uuid'])
         return course_runs, failure
diff --git a/openedx/core/djangoapps/catalog/tests/test_utils.py b/openedx/core/djangoapps/catalog/tests/test_utils.py
index bc5657d4a4..fb7a481c46 100644
--- a/openedx/core/djangoapps/catalog/tests/test_utils.py
+++ b/openedx/core/djangoapps/catalog/tests/test_utils.py
@@ -16,6 +16,7 @@ from course_modes.tests.factories import CourseModeFactory
 from entitlements.tests.factories import CourseEntitlementFactory
 from openedx.core.constants import COURSE_UNPUBLISHED
 from openedx.core.djangoapps.catalog.cache import (
+    COURSE_PROGRAMS_CACHE_KEY_TPL,
     PATHWAY_CACHE_KEY_TPL,
     PROGRAM_CACHE_KEY_TPL,
     SITE_PATHWAY_IDS_CACHE_KEY_TPL,
@@ -183,6 +184,27 @@ class TestGetPrograms(CacheIsolationTestCase):
         self.assertEqual(actual_program, expected_program)
         self.assertFalse(mock_warning.called)
 
+    def test_get_from_course(self, mock_warning, _mock_info):
+        expected_program = ProgramFactory()
+        expected_course = expected_program['courses'][0]['course_runs'][0]['key']
+
+        self.assertEqual(get_programs(course=expected_course), [])
+
+        cache.set(
+            COURSE_PROGRAMS_CACHE_KEY_TPL.format(course_run_id=expected_course),
+            [expected_program['uuid']],
+            None
+        )
+        cache.set(
+            PROGRAM_CACHE_KEY_TPL.format(uuid=expected_program['uuid']),
+            expected_program,
+            None
+        )
+
+        actual_program = get_programs(course=expected_course)
+        self.assertEqual(actual_program, [expected_program])
+        self.assertFalse(mock_warning.called)
+
 
 @skip_unless_lms
 @mock.patch(UTILS_MODULE + '.logger.info')
diff --git a/openedx/core/djangoapps/catalog/utils.py b/openedx/core/djangoapps/catalog/utils.py
index 6e07f41eb9..a1c219f72e 100644
--- a/openedx/core/djangoapps/catalog/utils.py
+++ b/openedx/core/djangoapps/catalog/utils.py
@@ -107,7 +107,9 @@ def get_programs(site=None, uuid=None, course=None):  # pylint: disable=redefine
     elif course:
         uuids = cache.get(COURSE_PROGRAMS_CACHE_KEY_TPL.format(course_run_id=course))
         if not uuids:
-            logger.warning(missing_details_msg_tpl.format(course=course))
+            # Currently, the cache does not differentiate between a cache miss and a course
+            # without programs. After this is changed, log any cache misses here.
+            return []
     else:
         uuids = cache.get(SITE_PROGRAM_UUIDS_CACHE_KEY_TPL.format(domain=site.domain), [])
         if not uuids: