Ordered subjects in course metadata courses

course_discovery/apps/course_metadata/migrations/0077_auto_20180126_1204.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.3 on 2018-01-26 12:04
+from __future__ import unicode_literals
+
+import sortedm2m.fields
+from django.db import migrations
+from sortedm2m.operations import AlterSortedManyToManyField
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('course_metadata', '0076_auto_20171219_1841'),
+    ]
+
+    operations = [
+        AlterSortedManyToManyField(
+            model_name='course',
+            name='subjects',
+            field=sortedm2m.fields.SortedManyToManyField(blank=True, help_text=None, to='course_metadata.Subject'),
+        ),
+    ]

course_discovery/apps/course_metadata/migrations/0078_merge_20180209_1044.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.3 on 2018-02-09 10:44
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('course_metadata', '0077_auto_20180131_1956'),
+        ('course_metadata', '0077_auto_20180126_1204'),
+    ]
+
+    operations = [
+    ]

course_discovery/apps/course_metadata/models.py

@@ -340,7 +340,7 @@ class Course(TimeStampedModel):
     full_description = models.TextField(default=None, null=True, blank=True)
     authoring_organizations = SortedManyToManyField(Organization, blank=True, related_name='authored_courses')
     sponsoring_organizations = SortedManyToManyField(Organization, blank=True, related_name='sponsored_courses')
-    subjects = models.ManyToManyField(Subject, blank=True)
+    subjects = SortedManyToManyField(Subject, blank=True)
     prerequisites = models.ManyToManyField(Prerequisite, blank=True)
     level_type = models.ForeignKey(LevelType, default=None, null=True, blank=True)
     expected_learning_items = SortedManyToManyField(ExpectedLearningItem, blank=True)

course_discovery/apps/publisher/api/v1/views.py

 import logging
 
+from collections import OrderedDict
 from edx_rest_api_client.client import EdxRestApiClient
 from edx_rest_framework_extensions.authentication import JwtAuthentication
 from rest_framework import permissions, serializers, status, viewsets
@@ -112,11 +113,12 @@ class CourseRunViewSet(viewsets.GenericViewSet):
         discovery_course.image.save(publisher_course.image.name, publisher_course.image.file)
         discovery_course.authoring_organizations.add(*publisher_course.organizations.all())
 
-        subjects = [subject for subject in set([
+        subjects = [subject for subject in [
             publisher_course.primary_subject,
             publisher_course.secondary_subject,
             publisher_course.tertiary_subject
-        ]) if subject]
+        ] if subject]
+        subjects = list(OrderedDict.fromkeys(subjects))
         discovery_course.subjects.add(*subjects)
 
         defaults = {