folders: Don't allow archiving a folder if it contains channels.

zerver/views/channel_folders.py

@@ -1,6 +1,7 @@
 from typing import Annotated
 
 from django.http import HttpRequest, HttpResponse
+from django.utils.translation import gettext as _
 from pydantic import Json, StringConstraints
 
 from zerver.actions.channel_folders import (
@@ -12,10 +13,12 @@ from zerver.actions.channel_folders import (
 )
 from zerver.decorator import require_realm_admin
 from zerver.lib.channel_folders import (
+    check_channel_folder_in_use,
     check_channel_folder_name,
     get_channel_folder_by_id,
     get_channel_folders_in_realm,
 )
+from zerver.lib.exceptions import JsonableError
 from zerver.lib.response import json_success
 from zerver.lib.typed_endpoint import PathOnly, typed_endpoint
 from zerver.models.channel_folders import ChannelFolder
@@ -71,6 +74,11 @@ def update_channel_folder(
 
     if is_archived is not None and channel_folder.is_archived != is_archived:
         if is_archived:
+            if check_channel_folder_in_use(channel_folder):
+                raise JsonableError(
+                    _("You need to remove all the channels from this folder to archive it.")
+                )
+
             do_archive_channel_folder(channel_folder, acting_user=user_profile)
         else:
             do_unarchive_channel_folder(channel_folder, acting_user=user_profile)