Update error messaging for progress page self-gen certs

Clean up docstrings for gen cert POST.

lms/djangoapps/courseware/tests/test_views.py

@@ -876,7 +876,6 @@ class GenerateUserCertTests(ModuleStoreTestCase):
             mock_send_to_queue.return_value = (0, "Successfully queued")
             resp = self.client.post(self.url)
             self.assertEqual(resp.status_code, 200)
-            self.assertIn("Creating certificate", resp.content)
 
             #Verify Google Analytics event fired after generating certificate
             mock_tracker.track.assert_called_once_with(  # pylint: disable=no-member
@@ -906,7 +905,7 @@ class GenerateUserCertTests(ModuleStoreTestCase):
         )
         resp = self.client.post(self.url)
         self.assertEqual(resp.status_code, HttpResponseBadRequest.status_code)
-        self.assertIn("Creating certificate", resp.content)
+        self.assertIn("Certificate is already being created.", resp.content)
 
     @patch('courseware.grades.grade', Mock(return_value={'grade': 'Pass', 'percent': 0.75}))
     def test_user_with_passing_existing_downloadable_cert(self):
@@ -920,7 +919,7 @@ class GenerateUserCertTests(ModuleStoreTestCase):
         )
         resp = self.client.post(self.url)
         self.assertEqual(resp.status_code, HttpResponseBadRequest.status_code)
-        self.assertIn("Creating certificate", resp.content)
+        self.assertIn("Certificate has already been created.", resp.content)
 
     def test_user_with_non_existing_course(self):
         # If try to access a course with valid key pattern then it will return

lms/djangoapps/courseware/views.py

@@ -1302,18 +1302,27 @@ def is_course_passed(course, grade_summary=None, student=None, request=None):
     return success_cutoff and grade_summary['percent'] > success_cutoff
 
 
-@ensure_csrf_cookie
 @require_POST
 def generate_user_cert(request, course_id):
-    """
-    It will check all validation and on clearance will add the new-certificate request into the xqueue.
+    """Start generating a new certificate for the user.
 
-     Args:
-        request (django request object):  the HTTP request object that triggered this view function
-        course_id (unicode):  id associated with the course
+    Certificate generation is allowed if:
+    * The user has passed the course, and
+    * The user does not already have a pending/completed certificate.
+
+    Note that if an error occurs during certificate generation
+    (for example, if the queue is down), then we simply mark the
+    certificate generation task status as "error" and re-run
+    the task with a management command.  To students, the certificate
+    will appear to be "generating" until it is re-run.
+
+    Args:
+        request (HttpRequest): The POST request to this view.
+        course_id (unicode): The identifier for the course.
 
     Returns:
-        returns json response
+        HttpResponse: 200 on success, 400 if a new certificate cannot be generated.
+
     """
 
     if not request.user.is_authenticated():
@@ -1325,7 +1334,6 @@ def generate_user_cert(request, course_id):
         )
 
     student = request.user
-
     course_key = CourseKey.from_string(course_id)
 
     course = modulestore().get_course(course_key, depth=2)
@@ -1337,17 +1345,20 @@ def generate_user_cert(request, course_id):
 
     certificate_status = certs_api.certificate_downloadable_status(student, course.id)
 
-    if not certificate_status["is_downloadable"] and not certificate_status["is_generating"]:
+    if certificate_status["is_downloadable"]:
+        return HttpResponseBadRequest(_("Certificate has already been created."))
+    elif certificate_status["is_generating"]:
+        return HttpResponseBadRequest(_("Certificate is already being created."))
+    else:
+        # If the certificate is not already in-process or completed,
+        # then create a new certificate generation task.
+        # If the certificate cannot be added to the queue, this will
+        # mark the certificate with "error" status, so it can be re-run
+        # with a management command.  From the user's perspective,
+        # it will appear that the certificate task was submitted successfully.
         certs_api.generate_user_certificates(student, course.id)
         _track_successful_certificate_generation(student.id, course.id)
-        return HttpResponse(_("Creating certificate"))
-
-    # if certificate_status is not is_downloadable and is_generating or
-    # if any error appears during certificate generation return the message cert is generating.
-    # with badrequest
-    # at backend debug the issue and re-submit the task.
-
-    return HttpResponseBadRequest(_("Creating certificate"))
+        return HttpResponse()
 
 
 def _track_successful_certificate_generation(user_id, course_id):  # pylint: disable=invalid-name
@@ -1355,7 +1366,7 @@ def _track_successful_certificate_generation(user_id, course_id):  # pylint: dis
 
     Arguments:
         user_id (str): The ID of the user generting the certificate.
-        course_id (unicode):  id associated with the course
+        course_id (CourseKey): Identifier for the course.
     Returns:
         None
 

lms/static/js/courseware/certificates_api.js

 $(document).ready(function() {
+    'use strict';
+
     $("#btn_generate_cert").click(function(e){
         e.preventDefault();
         var post_url = $("#btn_generate_cert").data("endpoint");