Remove JsonableErrors from actions.do_update_message.

There were a bunch of authorization and well-formedness checks in
zerver.lib.actions.do_update_message that I moved to
zerver.views.messages.update_message_backend.

Reason: by convention, functions in actions.py complete their actions;
error checking should be done outside the file when possible.

Fixes: #1150.

zerver/lib/actions.py

@@ -2377,45 +2377,14 @@ def update_user_message_flags(message, ums):
         um.save(update_fields=['flags'])
 
 
-def do_update_message(user_profile, message_id, subject, propagate_mode, content):
+def do_update_message(user_profile, message, subject, propagate_mode, content, rendered_content):
-    # type: (UserProfile, int, Optional[text_type], str, Optional[text_type]) -> None
+    # type: (UserProfile, Message, Optional[text_type], str, Optional[text_type], Optional[text_type]) -> None
-    try:
-        message = Message.objects.select_related().get(id=message_id)
-    except Message.DoesNotExist:
-        raise JsonableError(_("Unknown message id"))
-
     event = {'type': 'update_message',
              'sender': user_profile.email,
-             'message_id': message_id} # type: Dict[str, Any]
+             'message_id': message.id} # type: Dict[str, Any]
-    edit_history_event = {}
+    edit_history_event = {} # type: Dict[str, Any]
     changed_messages = [message]
 
-    # You only have permission to edit a message if:
-    # 1. You sent it, OR:
-    # 2. This is a topic-only edit for a (no topic) message, OR:
-    # 3. This is a topic-only edit and you are an admin.
-    if message.sender == user_profile:
-        pass
-    elif (content is None) and ((message.subject == "(no topic)") or
-                                user_profile.is_realm_admin):
-        pass
-    else:
-        raise JsonableError(_("You don't have permission to edit this message"))
-
-    # We already check for realm.allow_message_editing in
-    # zerver.views.messages.update_message_backend
-    # If there is a change to the content, we also need to check it hasn't been
-    # too long
-
-    # Allow an extra 20 seconds since we potentially allow editing 15 seconds
-    # past the limit, and in case there are network issues, etc. The 15 comes
-    # from (min_seconds_to_edit + seconds_left_buffer) in message_edit.js; if
-    # you change this value also change those two parameters in message_edit.js.
-    edit_limit_buffer = 20
-    if content is not None and user_profile.realm.message_content_edit_limit_seconds > 0 and \
-       (now() - message.pub_date) > datetime.timedelta(seconds=user_profile.realm.message_content_edit_limit_seconds + edit_limit_buffer):
-        raise JsonableError(_("The time limit for editing this message has past"))
-
     # Set first_rendered_content to be the oldest version of the
     # rendered content recorded; which is the current version if the
     # content hasn't been edited before.  Note that because one could
@@ -2428,17 +2397,9 @@ def do_update_message(user_profile, message_id, subject, propagate_mode, content
             if 'prev_rendered_content' in old_edit_history_event:
                 first_rendered_content = old_edit_history_event['prev_rendered_content']
 
-    ums = UserMessage.objects.filter(message=message_id)
+    ums = UserMessage.objects.filter(message=message.id)
 
     if content is not None:
-        if len(content.strip()) == 0:
-            content = "(deleted)"
-        content = truncate_body(content)
-        rendered_content = message.render_markdown(content)
-
-        if not rendered_content:
-            raise JsonableError(_("We were unable to render your updated message"))
-
         update_user_message_flags(message, ums)
 
         # We are turning off diff highlighting everywhere until ticket #1532 is addressed.
@@ -3347,4 +3308,3 @@ def check_attachment_reference_change(prev_content, message):
     to_add = list(new_attachments - prev_attachments)
     if len(to_add) > 1:
         do_claim_attachments(message)
-

zerver/tests/test_events.py

@@ -320,11 +320,12 @@ class EventsRegisterTest(AuthedTestCase):
             # it's kind of an unwanted but harmless side effect of calling log_event.
         ])
 
-        message_id = Message.objects.order_by('-id')[0].id
+        message = Message.objects.order_by('-id')[0]
         topic = 'new_topic'
         propagate_mode = 'change_all'
         content = 'new content'
-        events = self.do_test(lambda: do_update_message(self.user_profile, message_id, topic, propagate_mode, content))
+        rendered_content = message.render_markdown(content)
+        events = self.do_test(lambda: do_update_message(self.user_profile, message, topic, propagate_mode, content, rendered_content))
         error = schema_checker('events[0]', events[0])
         self.assert_on_error(error)
 

zerver/views/messages.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 
 from django.utils.translation import ugettext as _
+from django.utils.timezone import now
 from django.conf import settings
 from django.core import validators
 from django.core.exceptions import ValidationError
@@ -19,7 +20,7 @@ from zerver.lib import bugdown
 from zerver.lib.actions import recipient_for_emails, do_update_message_flags, \
     compute_mit_user_fullname, compute_irc_user_fullname, compute_jabber_user_fullname, \
     create_mirror_user_if_needed, check_send_message, do_update_message, \
-    extract_recipients
+    extract_recipients, truncate_body
 from zerver.lib.cache import generic_bulk_cached_fetch
 from zerver.lib.query import last_n
 from zerver.lib.response import json_success, json_error
@@ -41,7 +42,7 @@ from sqlalchemy.sql import select, join, column, literal_column, literal, and_,
 
 import re
 import ujson
-
+import datetime
 
 from six.moves import map
 import six
@@ -813,18 +814,50 @@ def update_message_backend(request, user_profile,
     if not user_profile.realm.allow_message_editing:
         return json_error(_("Your organization has turned off message editing."))
 
+    try:
+        message = Message.objects.select_related().get(id=message_id)
+    except Message.DoesNotExist:
+        raise JsonableError(_("Unknown message id"))
+
+    # You only have permission to edit a message if:
+    # 1. You sent it, OR:
+    # 2. This is a topic-only edit for a (no topic) message, OR:
+    # 3. This is a topic-only edit and you are an admin.
+    if message.sender == user_profile:
+        pass
+    elif (content is None) and ((message.subject == "(no topic)") or
+                                user_profile.is_realm_admin):
+        pass
+    else:
+        raise JsonableError(_("You don't have permission to edit this message"))
+
+    # If there is a change to the content, check that it hasn't been too long
+    # Allow an extra 20 seconds since we potentially allow editing 15 seconds
+    # past the limit, and in case there are network issues, etc. The 15 comes
+    # from (min_seconds_to_edit + seconds_left_buffer) in message_edit.js; if
+    # you change this value also change those two parameters in message_edit.js.
+    edit_limit_buffer = 20
+    if content is not None and user_profile.realm.message_content_edit_limit_seconds > 0 and \
+       (now() - message.pub_date) > datetime.timedelta(seconds=user_profile.realm.message_content_edit_limit_seconds + edit_limit_buffer):
+        raise JsonableError(_("The time limit for editing this message has past"))
+
     if subject is None and content is None:
         return json_error(_("Nothing to change"))
     if subject is not None:
         subject = subject.strip()
         if subject == "":
             raise JsonableError(_("Topic can't be empty"))
+    rendered_content = None
     if content is not None:
         content = content.strip()
         if content == "":
             raise JsonableError(_("Content can't be empty"))
+        content = truncate_body(content)
+        rendered_content = message.render_markdown(content)
+        if not rendered_content:
+            raise JsonableError(_("We were unable to render your updated message"))
 
-    do_update_message(user_profile, message_id, subject, propagate_mode, content)
+    do_update_message(user_profile, message, subject, propagate_mode, content, rendered_content)
     return json_success()
 
 @authenticated_json_post_view