Add "following" parameter to thread creation

This allows authors to follow the thread immediately upon creation.

lms/djangoapps/discussion_api/api.py

@@ -10,6 +10,7 @@ from opaque_keys import InvalidKeyError
 from opaque_keys.edx.locator import CourseLocator
 
 from courseware.courses import get_course_with_access
+from discussion_api.forms import ThreadCreateExtrasForm
 from discussion_api.pagination import get_paginated_data
 from discussion_api.serializers import CommentSerializer, ThreadSerializer, get_context
 from django_comment_client.base.views import (
@@ -243,17 +244,24 @@ def create_thread(request, thread_data):
 
     context = get_context(course, request)
     serializer = ThreadSerializer(data=thread_data, context=context)
-    if not serializer.is_valid():
-        raise ValidationError(serializer.errors)
+    extras_form = ThreadCreateExtrasForm(thread_data)
+    if not (serializer.is_valid() and extras_form.is_valid()):
+        raise ValidationError(dict(serializer.errors.items() + extras_form.errors.items()))
     serializer.save()
 
     thread = serializer.object
+    ret = serializer.data
+    following = extras_form.cleaned_data["following"]
+    if following:
+        context["cc_requester"].follow(thread)
+        ret["following"] = True
+
     track_forum_event(
         request,
         THREAD_CREATED_EVENT_NAME,
         course,
         thread,
-        get_thread_created_event_data(thread, followed=False)
+        get_thread_created_event_data(thread, followed=following)
     )
 
     return serializer.data

lms/djangoapps/discussion_api/forms.py

@@ -2,7 +2,7 @@
 Discussion API forms
 """
 from django.core.exceptions import ValidationError
-from django.forms import CharField, Form, IntegerField, NullBooleanField
+from django.forms import BooleanField, CharField, Form, IntegerField, NullBooleanField
 
 from opaque_keys import InvalidKeyError
 from opaque_keys.edx.locator import CourseLocator
@@ -37,6 +37,14 @@ class ThreadListGetForm(_PaginationForm):
             raise ValidationError("'{}' is not a valid course id".format(value))
 
 
+class ThreadCreateExtrasForm(Form):
+    """
+    A form to handle fields in thread creation that require separate
+    interactions with the comments service.
+    """
+    following = BooleanField(required=False)
+
+
 class CommentListGetForm(_PaginationForm):
     """
     A form to validate query parameters in the comment list retrieval endpoint

lms/djangoapps/discussion_api/tests/test_api.py

@@ -3,6 +3,7 @@ Tests for Discussion API internal interface
 """
 from datetime import datetime, timedelta
 import itertools
+from urlparse import urlparse
 
 import ddt
 import httpretty
@@ -1066,6 +1067,23 @@ class CreateThreadTest(CommentsServiceMockMixin, UrlResetMixin, ModuleStoreTestC
             }
         )
 
+    def test_following(self):
+        self.register_post_thread_response({"id": "test_id"})
+        self.register_subscription_response(self.user)
+        data = self.minimal_data.copy()
+        data["following"] = "True"
+        result = create_thread(self.request, data)
+        self.assertEqual(result["following"], True)
+        cs_request = httpretty.last_request()
+        self.assertEqual(
+            urlparse(cs_request.path).path,
+            "/api/v1/users/{}/subscriptions".format(self.user.id)
+        )
+        self.assertEqual(
+            cs_request.parsed_body,
+            {"source_type": ["thread"], "source_id": ["test_id"]}
+        )
+
     def test_course_id_missing(self):
         with self.assertRaises(ValidationError) as assertion:
             create_thread(self.request, {})

lms/djangoapps/discussion_api/tests/utils.py

@@ -74,6 +74,17 @@ class CommentsServiceMockMixin(object):
             status=200
         )
 
+    def register_subscription_response(self, user):
+        """
+        Register a mock response for POST on the CS user subscription endpoint
+        """
+        httpretty.register_uri(
+            httpretty.POST,
+            "http://localhost:4567/api/v1/users/{id}/subscriptions".format(id=user.id),
+            body=json.dumps({}),  # body is unused
+            status=200
+        )
+
     def assert_query_params_equal(self, httpretty_request, expected_params):
         """
         Assert that the given mock request had the expected query parameters

lms/djangoapps/discussion_api/views.py

@@ -96,6 +96,9 @@ class ThreadViewSet(_ViewMixin, DeveloperErrorViewMixin, ViewSet):
 
         * raw_body (required): The thread's raw body text
 
+        * following (optional): A boolean indicating whether the user should
+            follow the thread upon its creation; defaults to false
+
     **GET Response Values**:
 
         * results: The list of threads; each item in the list has the same