Fix trello integration by adding handling HEAD confirmation request.

Previously, we rejected the HEAD requests that the trello integration
uses to check if the server accepts the integration.

Add decorator for returning 200 status code if request is HEAD.

Fixes: #2311.

zerver/decorator.py

@@ -7,7 +7,7 @@ from django.views.decorators.csrf import csrf_exempt
 from django.http import QueryDict, HttpResponseNotAllowed, HttpRequest
 from django.http.multipartparser import MultiPartParser
 from zerver.models import UserProfile, get_client, get_user_profile_by_email
-from zerver.lib.response import json_error, json_unauthorized
+from zerver.lib.response import json_error, json_unauthorized, json_success
 from django.shortcuts import resolve_url
 from django.utils.decorators import available_attrs
 from django.utils.timezone import now
@@ -649,3 +649,13 @@ def uses_mandrill(func):
         kwargs['mail_client'] = get_mandrill_client()
         return func(*args, **kwargs)
     return wrapped_func # type: ignore # https://github.com/python/mypy/issues/1927
+
+def return_success_on_head_request(view_func):
+    # type: (Callable) -> Callable
+    @wraps(view_func)
+    def _wrapped_view_func(request, *args, **kwargs):
+        # type: (HttpResponse, *Any, **Any) -> Callable
+        if request.method == 'HEAD':
+            return json_success()
+        return view_func(request, *args, **kwargs)
+    return _wrapped_view_func

zerver/tests/test_decorators.py

@@ -17,6 +17,7 @@ from zerver.lib.test_classes import (
     ZulipTestCase,
     WebhookTestCase,
 )
+from zerver.lib.response import json_response
 from zerver.lib.request import \
     REQ, has_request_variables, RequestVariableMissingError, \
     RequestVariableConversionError, JsonableError
@@ -25,7 +26,8 @@ from zerver.decorator import (
     authenticated_json_post_view, authenticated_json_view,
     authenticate_notify,
     get_client_name, internal_notify_view, is_local_addr,
-    rate_limit, validate_api_key, logged_in_and_active
+    rate_limit, validate_api_key, logged_in_and_active,
+    return_success_on_head_request
     )
 from zerver.lib.validator import (
     check_string, check_dict, check_bool, check_int, check_list
@@ -872,3 +874,31 @@ class TestZulipLoginRequiredDecorator(ZulipTestCase):
             with mock.patch('zerver.decorator.get_subdomain', return_value='acme'):
                 result = self.client_get('/accounts/accept_terms/')
                 self.assertEqual(result.status_code, 302)
+
+class ReturnSuccessOnHeadRequestDecorator(ZulipTestCase):
+    def test_return_success_on_head_request_returns_200_if_request_method_is_head(self):
+        class HeadRequest(object):
+            method = 'HEAD'
+
+        request = HeadRequest()
+
+        @return_success_on_head_request
+        def test_function(request):
+            return json_response(msg=u'from_test_function')
+
+        response = test_function(request)
+        self.assert_json_success(response)
+        self.assertNotEqual(ujson.loads(response.content).get('msg'), u'from_test_function')
+
+    def test_return_success_on_head_request_returns_normal_response_if_request_method_is_not_head(self):
+            class HeadRequest(object):
+                method = 'POST'
+
+            request = HeadRequest()
+
+            @return_success_on_head_request
+            def test_function(request):
+                return json_response(msg=u'from_test_function')
+
+            response = test_function(request)
+            self.assertEqual(ujson.loads(response.content).get('msg'), u'from_test_function')

zerver/tests/webhooks/test_trello.py

@@ -6,6 +6,11 @@ class TrelloHookTests(WebhookTestCase):
     URL_TEMPLATE = u"/api/v1/external/trello?stream={stream}&api_key={api_key}"
     FIXTURE_DIR_NAME = 'trello'
 
+    def test_trello_confirmation_request(self):
+        # type: () -> None
+        response = self.client.head(self.build_webhook_url())
+        self.assertEqual(response.status_code, 200, response)
+
     def test_trello_webhook_when_card_was_moved_to_another_list(self):
         # type: () -> None
         expected_message = u"TomaszKolek moved [This is a card.](https://trello.com/c/r33ylX2Z) from Basics to Intermediate."

zerver/views/webhooks/trello/__init__.py

@@ -6,6 +6,7 @@ from typing import Mapping, Any, Tuple
 from django.utils.translation import ugettext as _
 from django.http import HttpRequest, HttpResponse
 from zerver.lib.actions import check_send_message
+from zerver.decorator import return_success_on_head_request
 from zerver.lib.response import json_success, json_error
 from zerver.models import UserProfile, Client
 from zerver.decorator import REQ, has_request_variables, api_key_only_webhook_view
@@ -15,6 +16,7 @@ from .board_actions import SUPPORTED_BOARD_ACTIONS, process_board_action
 from .exceptions import UnsupportedAction
 
 @api_key_only_webhook_view('Trello')
+@return_success_on_head_request
 @has_request_variables
 def api_trello_webhook(request, user_profile, client, payload=REQ(argument_type='body'), stream=REQ(default='trello')):
     # type: (HttpRequest, UserProfile, Client, Mapping[str, Any], text_type) -> HttpResponse