[SE-3329] Expose banner image url in course API

lms/djangoapps/course_api/serializers.py

@@ -31,6 +31,38 @@ def get_uri(self, course_overview):
         return getattr(course_overview, self.uri_attribute)
 
 
+class _AbsolutMediaSerializer(_MediaSerializer):  # pylint: disable=abstract-method
+    """
+    Nested serializer to represent a media object and its absolute path.
+    """
+    requires_context = True
+
+    def __call__(self, serializer_field):
+        self.context = serializer_field.context
+        return super(self).__call__(serializer_field)
+
+    url = serializers.SerializerMethodField(source="*")
+
+    def get_url(self, course_overview):
+        """
+        Convert the media resource's URI to an absolute URL
+        """
+        uri = getattr(course_overview, self.uri_attribute)
+
+        if not uri:
+            return
+
+        url = course_overview.apply_cdn_to_url(uri)
+        field = AbsoluteURLField()
+
+        # In order to use the AbsoluteURLField to have the same
+        # behaviour what ImageSerializer provides, we need to set
+        # the request for the field
+        field._context = {"request": self.context.get("request")}
+
+        return field.to_representation(url)
+
+
 class ImageSerializer(serializers.Serializer):  # pylint: disable=abstract-method
     """
     Collection of URLs pointing to images of various sizes.
@@ -47,6 +79,7 @@ class _CourseApiMediaCollectionSerializer(serializers.Serializer):  # pylint: di
     """
     Nested serializer to represent a collection of media objects
     """
+    banner_image = _AbsolutMediaSerializer(source='*', uri_attribute='banner_image_url')
     course_image = _MediaSerializer(source='*', uri_attribute='course_image_url')
     course_video = _MediaSerializer(source='*', uri_attribute='course_video_url')
     image = ImageSerializer(source='image_urls')

lms/djangoapps/course_api/tests/test_serializers.py

@@ -39,15 +39,22 @@ def setUp(self):
         self.honor_user = self.create_user('honor', is_staff=False)
         self.request_factory = APIRequestFactory()
 
+        course_id = u'edX/toy/2012_Fall'
+        banner_image_path = u'/c4x/edX/toy/asset/images_course_image.jpg'
+        banner_image_url = u'http://testserver' + banner_image_path
         image_path = u'/c4x/edX/toy/asset/just_a_test.jpg'
         image_url = u'http://testserver' + image_path
         self.expected_data = {
-            'id': u'edX/toy/2012_Fall',
+            'id': course_id,
             'name': u'Toy Course',
             'number': u'toy',
             'org': u'edX',
             'short_description': u'A course about toys.',
             'media': {
+                'banner_image': {
+                    'uri': banner_image_path,
+                    'url': banner_image_url,
+                },
                 'course_image': {
                     'uri': image_path,
                 },
@@ -74,7 +81,7 @@ def setUp(self):
             'invitation_only': False,
 
             # 'course_id' is a deprecated field, please use 'id' instead.
-            'course_id': u'edX/toy/2012_Fall',
+            'course_id': course_id,
         }
 
     def _get_request(self, user=None):

openedx/core/djangoapps/content/course_overviews/migrations/0023_auto_20200922_1245.py

@@ -0,0 +1,23 @@
+# Generated by Django 2.2.16 on 2020-09-22 12:45
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('course_overviews', '0022_courseoverviewtab_is_hidden'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='courseoverview',
+            name='banner_image_url',
+            field=models.TextField(null=True),
+        ),
+        migrations.AddField(
+            model_name='historicalcourseoverview',
+            name='banner_image_url',
+            field=models.TextField(null=True),
+        ),
+    ]

openedx/core/djangoapps/content/course_overviews/models.py

@@ -63,7 +63,7 @@ class Meta(object):
         app_label = 'course_overviews'
 
     # IMPORTANT: Bump this whenever you modify this model and/or add a migration.
-    VERSION = 11  # this one goes to eleven
+    VERSION = 12  # this one goes to thirteen
 
     # Cache entry versioning.
     version = IntegerField()
@@ -86,6 +86,7 @@ class Meta(object):
     announcement = DateTimeField(null=True)
 
     # URLs
+    banner_image_url = TextField(null=True)
     course_image_url = TextField()
     social_sharing_url = TextField(null=True)
     end_of_course_survey_url = TextField(null=True)
@@ -196,6 +197,7 @@ def _create_or_update(cls, course):
         course_overview.advertised_start = course.advertised_start
         course_overview.announcement = course.announcement
 
+        course_overview.banner_image_url = CourseDetails.fetch_banner_image_url(course.id)
         course_overview.course_image_url = course_image_url(course)
         course_overview.social_sharing_url = course.social_sharing_url
 
@@ -728,6 +730,21 @@ def closest_released_language(self):
         """
         return get_closest_released_language(self.language) if self.language else None
 
+    def apply_cdn_to_url(self, image_url):
+        """
+        Given a resolution -> url, return a copy with CDN applied.
+
+        If CDN does not exist or is disabled, just returns the original. The
+        URL that we store in CourseOverviewImageSet is already top level path,
+        so we don't need to go through the /static remapping magic that happens
+        with other course assets. We just need to add the CDN server if appropriate.
+        """
+        cdn_config = AssetBaseUrlConfig.current()
+        if not cdn_config.enabled:
+            return image_url
+
+        return self._apply_cdn_to_url(image_url, cdn_config.base_url)
+
     def apply_cdn_to_urls(self, image_urls):
         """
         Given a dict of resolutions -> urls, return a copy with CDN applied.
@@ -738,14 +755,8 @@ def apply_cdn_to_urls(self, image_urls):
         happens with other course assets. We just need to add the CDN server if
         appropriate.
         """
-        cdn_config = AssetBaseUrlConfig.current()
-        if not cdn_config.enabled:
-            return image_urls
-
-        base_url = cdn_config.base_url
-
         return {
-            resolution: self._apply_cdn_to_url(url, base_url)
+            resolution: self.apply_cdn_to_url(url)
             for resolution, url in image_urls.items()
         }
 

openedx/core/djangoapps/content/course_overviews/tests/test_course_overviews.py

@@ -382,7 +382,7 @@ def test_malformed_grading_policy(self):
         course_overview = CourseOverview._create_or_update(course)  # pylint: disable=protected-access
         self.assertEqual(course_overview.lowest_passing_grade, None)
 
-    @ddt.data((ModuleStoreEnum.Type.mongo, 4, 4), (ModuleStoreEnum.Type.split, 3, 4))
+    @ddt.data((ModuleStoreEnum.Type.mongo, 5, 5), (ModuleStoreEnum.Type.split, 3, 3))
     @ddt.unpack
     def test_versioning(self, modulestore_type, min_mongo_calls, max_mongo_calls):
         """
@@ -789,6 +789,25 @@ def test_cdn_with_external_image(self, modulestore_type):
             self.assertTrue(modified_urls['small'].startswith(expected_cdn_url))
             self.assertEqual(modified_urls['large'], start_urls['large'])
 
+    @ddt.data(ModuleStoreEnum.Type.mongo, ModuleStoreEnum.Type.split)
+    def test_cdn_with_a_single_external_image(self, modulestore_type):
+        """
+        Test that we return CDN prefixed URLs unless they're absolute.
+        """
+        with self.store.default_store(modulestore_type):
+            course = CourseFactory.create(default_store=modulestore_type)
+            overview = CourseOverview.get_from_id(course.id)
+
+            # Now enable the CDN...
+            AssetBaseUrlConfig.objects.create(enabled=True, base_url='fakecdn.edx.org')
+            expected_cdn_url = "//fakecdn.edx.org"
+
+            start_url = "/static/overview.png"
+            modified_url = overview.apply_cdn_to_url(start_url)
+
+            self.assertNotEqual(start_url, modified_url)
+            self.assertTrue(modified_url.startswith(expected_cdn_url))
+
     @ddt.data(ModuleStoreEnum.Type.mongo, ModuleStoreEnum.Type.split)
     def test_error_generating_thumbnails(self, modulestore_type):
         """

openedx/core/djangoapps/models/course_details.py

@@ -91,6 +91,13 @@ def fetch_about_attribute(cls, course_key, attribute):
             value = None
         return value
 
+    @classmethod
+    def fetch_banner_image_url(cls, course_key):
+        """
+        Fetch only the banner image url of the given course from the descriptor.
+        """
+        return course_image_url(modulestore().get_course(course_key), 'banner_image')
+
     @classmethod
     def fetch(cls, course_key):
         """

openedx/core/djangoapps/models/tests/test_course_details.py

@@ -179,3 +179,12 @@ def test_fetch_video(self):
         self.assertEqual(CourseDetails.fetch_youtube_video_id(self.course.id), video_value)
         video_url = CourseDetails.fetch_video_url(self.course.id)
         self.assertRegex(video_url, r'http://.*{}'.format(video_value))
+
+    def test_fetch_banner_image_url(self):
+        course_details = CourseDetails.fetch(self.course.id)
+        banner_image_asset_path = CourseDetails.fetch_banner_image_url(self.course.id)
+
+        self.assertEqual(
+            course_details.banner_image_asset_path,
+            banner_image_asset_path
+        )