Add option to disable searching in the user dir

We still populate it, as it can still be accessed via the admin API.

synapse/config/user_directory.py

@@ -22,9 +22,13 @@ class UserDirectoryConfig(Config):
     """
 
     def read_config(self, config):
+        self.user_directory_search_enabled = True
         self.user_directory_search_all_users = False
         user_directory_config = config.get("user_directory", None)
         if user_directory_config:
+            self.user_directory_search_enabled = (
+                user_directory_config.get("enabled", True)
+            )
             self.user_directory_search_all_users = (
                 user_directory_config.get("search_all_users", False)
             )
@@ -33,6 +37,8 @@ class UserDirectoryConfig(Config):
         return """
         # User Directory configuration
         #
+        # 'enabled' defines whether users can search the user directory,
+        #  defaults to True.
         # 'search_all_users' defines whether to search all users visible to your HS
         # when searching the user directory, rather than limiting to users visible
         # in public rooms.  Defaults to false.  If you set it True, you'll have to run
@@ -40,5 +46,6 @@ class UserDirectoryConfig(Config):
         # on your database to tell it to rebuild the user_directory search indexes.
         #
         #user_directory:
+        #  enabled: true
         #  search_all_users: false
         """

synapse/rest/client/v2_alpha/user_directory.py

@@ -59,6 +59,12 @@ class UserDirectorySearchRestServlet(RestServlet):
         requester = yield self.auth.get_user_by_req(request, allow_guest=False)
         user_id = requester.user.to_string()
 
+        if not self.hs.config.user_directory_search_enabled:
+            defer.returnValue((200, {
+                "limited": False,
+                "results": [],
+            }))
+
         body = parse_json_object_from_request(request)
 
         limit = body.get("limit", 10)