messages: Add support for quickly deleting all messages in a topic.

This is primarily a feature for onboarding, where an organization
administrator might send a bunch of random test messages as part of
joining, but then want a pristine organization when their users later
join.

But it can theoretically be used for other use cases (e.g. for
moderation or removing threads that are problematic in some way).

Tweaked by tabbott to handle corner cases with
is_history_public_to_subscribers.

Fixes #10912.

frontend_tests/node_tests/templates.js

@@ -1339,12 +1339,33 @@ run_test('topic_sidebar_actions', () => {
         stream_name: 'social',
         topic_name: 'lunch',
         can_mute_topic: true,
+        is_admin: false,
     };
     var html = render('topic_sidebar_actions', args);
 
     var a = $(html).find("a.narrow_to_topic");
     assert.equal(a.text().trim(), 'translated: Narrow to topic lunch');
 
+    var delete_topic_option = $(html).find("a.sidebar-popover-delete-topic-messages");
+    assert.equal(delete_topic_option.length, 0);
+
+    args = {
+        is_admin: true,
+    };
+    html = render('topic_sidebar_actions', args);
+
+    delete_topic_option = $(html).find("a.sidebar-popover-delete-topic-messages");
+    assert.equal(delete_topic_option.length, 1);
+});
+
+run_test('delete_topic_modal', () => {
+    var args = {
+        topic_name: 'lunch',
+    };
+    var html = render('delete_topic_modal', args);
+
+    var modal_body = $(html).find('.modal-body');
+    assert.equal(modal_body.text().trim(), 'translated: Delete all messages in topic lunch?');
 });
 
 run_test('typeahead_list_item', () => {

static/js/message_edit.js

@@ -641,6 +641,18 @@ exports.delete_message = function (msg_id) {
     });
 };
 
+exports.delete_topic = function (stream_id, topic_name) {
+    channel.post({
+        url: "/json/streams/" + stream_id + "/delete_topic",
+        data: {
+            topic_name: topic_name,
+        },
+        success: function () {
+            $('#delete_topic_modal').modal('hide');
+        },
+    });
+};
+
 exports.handle_narrow_deactivated = function () {
     _.each(currently_editing_messages, function (elem, idx) {
         if (current_msg_list.get(idx) !== undefined) {

static/js/stream_popover.js

@@ -152,6 +152,7 @@ function build_topic_popover(e) {
         topic_name: topic_name,
         can_mute_topic: can_mute_topic,
         can_unmute_topic: can_unmute_topic,
+        is_admin: sub.is_admin,
     });
 
     $(elt).popover({
@@ -375,6 +376,31 @@ exports.register_topic_handlers = function () {
         unread_ops.mark_topic_as_read(stream_id, topic);
         e.stopPropagation();
     });
+
+    // Deleting all message in a topic
+    $('body').on('click', '.sidebar-popover-delete-topic-messages', function (e) {
+        var stream_id = topic_popover_stream_id(e);
+        if (!stream_id) {
+            return;
+        }
+
+        var topic = $(e.currentTarget).attr('data-topic-name');
+        var args = {
+            topic_name: topic,
+        };
+
+        exports.hide_topic_popover();
+
+        $('#delete-topic-modal-holder').html(templates.render('delete_topic_modal', args));
+
+        $('#do_delete_topic_button').on('click', function () {
+            message_edit.delete_topic(stream_id, topic);
+        });
+
+        $('#delete_topic_modal').modal('show');
+
+        e.stopPropagation();
+    });
 };
 
 return exports;

static/templates/delete_topic_modal.handlebars

@@ -0,0 +1,15 @@
+<div id="delete_topic_modal" class="modal modal-bg hide fade new-style" tabindex="-1" role="dialog" aria-labelledby="delete_topic_modal_label" aria-hidden="true">
+    <div class="modal-header">
+        <button type="button" class="close" data-dismiss="modal" aria-label="{{t 'Close' }}"><span aria-hidden="true">&times;</span></button>
+        <h3 id="delete_topic_modal_label">{{t "Delete topic" }} </h3>
+    </div>
+    <div class="modal-body">
+        <p>{{#tr this}}Delete all messages in topic <b>__topic_name__</b>?{{/tr}}</p>
+    </div>
+    <div class="modal-footer">
+        <button class="button" data-dismiss="modal">{{t "Cancel" }}</button>
+        <button class="button btn-danger rounded" id="do_delete_topic_button">
+            {{t "Delete" }}
+        </button>
+    </div>
+</div>

static/templates/topic_sidebar_actions.handlebars

@@ -31,5 +31,13 @@
         </a>
     </li>
 
+    {{#if is_admin}}
+    <li>
+        <a class="sidebar-popover-delete-topic-messages" data-stream-id="{{ stream_id }}" data-topic-name="{{ topic_name }}">
+            <i class="fa fa-trash" aria-hidden="true"></i>
+            {{#tr this}}Delete all messages in <b>__topic_name__</b>{{/tr}}
+        </a>
+    </li>
+    {{/if}}
 
 </ul>

templates/zerver/app/index.html

@@ -167,5 +167,6 @@
     {% include "zerver/app/deprecation_notice.html" %}
     <div id="user-profile-modal-holder"></div>
     <div class='notifications top-right'></div>
+    <div id="delete-topic-modal-holder"></div>
 </div>
 {% endblock %}

zerver/tests/test_messages.py

@@ -277,6 +277,59 @@ class TopicHistoryTest(ZulipTestCase):
         result = self.client_get(endpoint, dict())
         self.assert_json_error(result, 'Invalid stream id')
 
+class TopicDeleteTest(ZulipTestCase):
+    def test_topic_delete(self) -> None:
+        initial_last_msg_id = self.get_last_message().id
+        stream_name = 'new_stream'
+        topic_name = 'new topic 2'
+
+        # NON-ADMIN USER
+        user_profile = self.example_user('hamlet')
+        self.subscribe(user_profile, stream_name)
+
+        # Send message
+        stream = get_stream(stream_name, user_profile.realm)
+        self.send_stream_message(user_profile.email, stream_name, topic_name=topic_name)
+        last_msg_id = self.send_stream_message(user_profile.email, stream_name, topic_name=topic_name)
+
+        # Deleting the topic
+        self.login(user_profile.email, realm=user_profile.realm)
+        endpoint = '/json/streams/' + str(stream.id) + '/delete_topic'
+        result = self.client_post(endpoint, {
+            "topic_name": topic_name
+        })
+        self.assert_json_error(result, "Must be an organization administrator")
+        self.assertEqual(self.get_last_message().id, last_msg_id)
+
+        # Make stream private with limited history
+        do_change_stream_invite_only(stream, invite_only=True,
+                                     history_public_to_subscribers=False)
+
+        # ADMIN USER subscribed now
+        user_profile = self.example_user('iago')
+        self.subscribe(user_profile, stream_name)
+        self.login(user_profile.email, realm=user_profile.realm)
+        new_last_msg_id = self.send_stream_message(user_profile.email, stream_name, topic_name=topic_name)
+
+        # Now admin deletes all messages in topic -- which should only
+        # delete new_last_msg_id, i.e. the one sent since they joined.
+        self.assertEqual(self.get_last_message().id, new_last_msg_id)
+        result = self.client_post(endpoint, {
+            "topic_name": topic_name
+        })
+        self.assert_json_success(result)
+        self.assertEqual(self.get_last_message().id, last_msg_id)
+
+        # Make the stream's history public to subscribers
+        do_change_stream_invite_only(stream, invite_only=True,
+                                     history_public_to_subscribers=True)
+        # Delete the topic should now remove all messages
+        result = self.client_post(endpoint, {
+            "topic_name": topic_name
+        })
+        self.assert_json_success(result)
+        self.assertEqual(self.get_last_message().id, initial_last_msg_id)
+
 class TestCrossRealmPMs(ZulipTestCase):
     def make_realm(self, domain: str) -> Realm:
         realm = Realm.objects.create(string_id=domain, invite_required=False)

zerver/views/streams.py

@@ -22,16 +22,17 @@ from zerver.lib.actions import bulk_remove_subscriptions, \
     do_create_default_stream_group, do_add_streams_to_default_stream_group, \
     do_remove_streams_from_default_stream_group, do_remove_default_stream_group, \
     do_change_default_stream_group_description, do_change_default_stream_group_name, \
-    prep_stream_welcome_message, do_change_stream_announcement_only
+    prep_stream_welcome_message, do_change_stream_announcement_only, \
+    do_delete_messages
 from zerver.lib.response import json_success, json_error, json_response
 from zerver.lib.streams import access_stream_by_id, access_stream_by_name, \
     check_stream_name, check_stream_name_available, filter_stream_authorization, \
     list_to_streams, access_stream_for_delete_or_update, access_default_stream_group_by_id
-from zerver.lib.topic import get_topic_history_for_stream
+from zerver.lib.topic import get_topic_history_for_stream, messages_for_topic
 from zerver.lib.validator import check_string, check_int, check_list, check_dict, \
     check_bool, check_variable_type, check_capped_string, check_color, check_dict_only
 from zerver.models import UserProfile, Stream, Realm, Subscription, \
-    Recipient, get_recipient, get_stream, \
+    Recipient, Message, UserMessage, get_recipient, get_stream, \
     get_system_bot, get_active_user
 
 from collections import defaultdict
@@ -453,6 +454,25 @@ def get_topics_backend(request: HttpRequest, user_profile: UserProfile,
 
     return json_success(dict(topics=result))
 
+@require_realm_admin
+@has_request_variables
+def delete_in_topic(request: HttpRequest, user_profile: UserProfile,
+                    stream_id: int=REQ(converter=to_non_negative_int),
+                    topic_name: str=REQ("topic_name")) -> HttpResponse:
+    (stream, recipient, sub) = access_stream_by_id(user_profile, stream_id)
+
+    messages = messages_for_topic(stream.id, topic_name)
+    if not stream.is_history_public_to_subscribers():
+        # Don't allow the user to delete messages that they don't have access to.
+        deletable_message_ids = UserMessage.objects.filter(
+            user_profile=user_profile, message_id__in=messages).values_list("message_id", flat=True)
+        messages = [message for message in messages if message.id in
+                    deletable_message_ids]
+
+    do_delete_messages(user_profile, messages)
+
+    return json_success()
+
 @authenticated_json_post_view
 @has_request_variables
 def json_stream_exists(request: HttpRequest, user_profile: UserProfile, stream_name: str=REQ("stream"),

zproject/urls.py

@@ -329,6 +329,11 @@ v1_api_and_json_patterns = [
     url(r'^streams/(?P<stream_id>\d+)$', rest_dispatch,
         {'PATCH': 'zerver.views.streams.update_stream_backend',
          'DELETE': 'zerver.views.streams.deactivate_stream_backend'}),
+
+    # Delete topic in stream
+    url(r'^streams/(?P<stream_id>\d+)/delete_topic$', rest_dispatch,
+        {'POST': 'zerver.views.streams.delete_in_topic'}),
+
     url(r'^default_streams$', rest_dispatch,
         {'POST': 'zerver.views.streams.add_default_stream',
          'DELETE': 'zerver.views.streams.remove_default_stream'}),