Fix unable to view ORA responses (files) in leaderboard

EDUCATOR-560

AUTHORS

@@ -28,3 +28,4 @@ Mushtaq Ali <mushtaak@gmail.com>
 Dmitry Viskov <dmitry.viskov@webenterprise.ru>
 Jeff LaJoie <jlajoie@edx.org>
 Albert St. Aubin Jr. <astaubin@edx.org>
+Awais Jibran <awaisdar001@gmail.com>

openassessment/xblock/leaderboard_mixin.py

@@ -76,16 +76,18 @@ class LeaderboardMixin(object):
         for score in scores:
             score['files'] = []
             if 'file_keys' in score['content']:
-                for key in score['content']['file_keys']:
-                    url = ''
-                    try:
-                        url = file_upload_api.get_download_url(key)
-                    except FileUploadError:
-                        pass
-                    if url:
-                        score['files'].append(url)
+                file_keys = score['content'].get('file_keys', [])
+                descriptions = score['content'].get('files_descriptions', [])
+                for idx, key in enumerate(file_keys):
+                    file_download_url = self._get_file_download_url(key)
+                    if file_download_url:
+                        file_description = descriptions[idx] if idx < len(descriptions) else ''
+                        score['files'].append((file_download_url, file_description))
+
             elif 'file_key' in score['content']:
-                score['files'].append(file_upload_api.get_download_url(score['content']['file_key']))
+                file_download_url = self._get_file_download_url(score['content']['file_key'])
+                if file_download_url:
+                    score['files'].append((file_download_url, ''))
             if 'text' in score['content'] or 'parts' in score['content']:
                 submission = {'answer': score.pop('content')}
                 score['submission'] = create_submission_dict(submission, self.prompts)
@@ -112,3 +114,19 @@ class LeaderboardMixin(object):
             template_path (string), tuple of context (dict)
         """
         return 'openassessmentblock/leaderboard/oa_leaderboard_waiting.html', {'xblock_id': self.get_xblock_id()}
+
+    def _get_file_download_url(self, file_key):
+        """
+        Internal function for retrieving the download url at which the file that corresponds
+        to the file_key can be downloaded.
+
+        Arguments:
+            file_key (string): Corresponding file key.
+        Returns:
+            file_download_url (string) or empty string in case of error.
+        """
+        try:
+            file_download_url = file_upload_api.get_download_url(file_key)
+        except FileUploadError:
+            file_download_url = ''
+        return file_download_url