Add the ability to exclude remote users in user directory search results (#18300)

This change adds a new configuration
`user_directory.exclude_remote_users`, which defaults to False.
When set to True, remote users will not appear in user directory search
results.

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before submitting your pull request -->

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- Be a short description of your change which makes sense to users.
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---------

Co-authored-by: Andrew Morgan <[email protected]>

Author: wrjlewis

changelog.d/18300.feature

@@ -0,0 +1 @@
+Add config option `user_directory.exclude_remote_users` which, when enabled, excludes remote users from user directory search results.

docs/usage/configuration/config_documentation.md

@@ -4095,6 +4095,7 @@ This option has the following sub-options:
 * `prefer_local_users`: Defines whether to prefer local users in search query results.
    If set to true, local users are more likely to appear above remote users when searching the
    user directory. Defaults to false.
+* `exclude_remote_users`: If set to true, the search will only return local users. Defaults to false.
 * `show_locked_users`: Defines whether to show locked users in search query results. Defaults to false.
 
 Example configuration:
@@ -4103,6 +4104,7 @@ user_directory:
     enabled: false
     search_all_users: true
     prefer_local_users: true
+    exclude_remote_users: false
     show_locked_users: true
 ```
 ---

synapse/config/user_directory.py

@@ -38,6 +38,9 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
         self.user_directory_search_all_users = user_directory_config.get(
             "search_all_users", False
         )
+        self.user_directory_exclude_remote_users = user_directory_config.get(
+            "exclude_remote_users", False
+        )
         self.user_directory_search_prefer_local_users = user_directory_config.get(
             "prefer_local_users", False
         )

synapse/handlers/user_directory.py

@@ -108,6 +108,9 @@ def __init__(self, hs: "HomeServer"):
         self.is_mine_id = hs.is_mine_id
         self.update_user_directory = hs.config.worker.should_update_user_directory
         self.search_all_users = hs.config.userdirectory.user_directory_search_all_users
+        self.exclude_remote_users = (
+            hs.config.userdirectory.user_directory_exclude_remote_users
+        )
         self.show_locked_users = hs.config.userdirectory.show_locked_users
         self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self._hs = hs

synapse/storage/databases/main/user_directory.py

@@ -1037,11 +1037,11 @@ async def search_user_dir(
                 }
         """
 
+        join_args: Tuple[str, ...] = (user_id,)
+
         if self.hs.config.userdirectory.user_directory_search_all_users:
-            join_args = (user_id,)
             where_clause = "user_id != ?"
         else:
-            join_args = (user_id,)
             where_clause = """
                 (
                     EXISTS (select 1 from users_in_public_rooms WHERE user_id = t.user_id)
@@ -1055,6 +1055,14 @@ async def search_user_dir(
         if not show_locked_users:
             where_clause += " AND (u.locked IS NULL OR u.locked = FALSE)"
 
+        # Adjust the JOIN type based on the exclude_remote_users flag (the users
+        # table only contains local users so an inner join is a good way to
+        # to exclude remote users)
+        if self.hs.config.userdirectory.user_directory_exclude_remote_users:
+            join_type = "JOIN"
+        else:
+            join_type = "LEFT JOIN"
+
         # We allow manipulating the ranking algorithm by injecting statements
         # based on config options.
         additional_ordering_statements = []
@@ -1086,7 +1094,7 @@ async def search_user_dir(
                 SELECT d.user_id AS user_id, display_name, avatar_url
                 FROM matching_users as t
                 INNER JOIN user_directory AS d USING (user_id)
-                LEFT JOIN users AS u ON t.user_id = u.name
+                %(join_type)s users AS u ON t.user_id = u.name
                 WHERE
                     %(where_clause)s
                 ORDER BY
@@ -1115,6 +1123,7 @@ async def search_user_dir(
             """ % {
                 "where_clause": where_clause,
                 "order_case_statements": " ".join(additional_ordering_statements),
+                "join_type": join_type,
             }
             args = (
                 (full_query,)
@@ -1142,7 +1151,7 @@ async def search_user_dir(
                 SELECT d.user_id AS user_id, display_name, avatar_url
                 FROM user_directory_search as t
                 INNER JOIN user_directory AS d USING (user_id)
-                LEFT JOIN users AS u ON t.user_id = u.name
+                %(join_type)s users AS u ON t.user_id = u.name
                 WHERE
                     %(where_clause)s
                     AND value MATCH ?
@@ -1155,6 +1164,7 @@ async def search_user_dir(
             """ % {
                 "where_clause": where_clause,
                 "order_statements": " ".join(additional_ordering_statements),
+                "join_type": join_type,
             }
             args = join_args + (search_query,) + ordering_arguments + (limit + 1,)
         else:

tests/handlers/test_user_directory.py

@@ -992,6 +992,67 @@ def test_prefer_local_users(self) -> None:
         [self.assertIn(user, local_users) for user in received_user_id_ordering[:3]]
         [self.assertIn(user, remote_users) for user in received_user_id_ordering[3:]]
 
+    @override_config(
+        {
+            "user_directory": {
+                "enabled": True,
+                "search_all_users": True,
+                "exclude_remote_users": True,
+            }
+        }
+    )
+    def test_exclude_remote_users(self) -> None:
+        """Tests that only local users are returned when
+        user_directory.exclude_remote_users is True.
+        """
+
+        # Create a room and few users to test the directory with
+        searching_user = self.register_user("searcher", "password")
+        searching_user_tok = self.login("searcher", "password")
+
+        room_id = self.helper.create_room_as(
+            searching_user,
+            room_version=RoomVersions.V1.identifier,
+            tok=searching_user_tok,
+        )
+
+        # Create a few local users and join them to the room
+        local_user_1 = self.register_user("user_xxxxx", "password")
+        local_user_2 = self.register_user("user_bbbbb", "password")
+        local_user_3 = self.register_user("user_zzzzz", "password")
+
+        self._add_user_to_room(room_id, RoomVersions.V1, local_user_1)
+        self._add_user_to_room(room_id, RoomVersions.V1, local_user_2)
+        self._add_user_to_room(room_id, RoomVersions.V1, local_user_3)
+
+        # Create a few "remote" users and join them to the room
+        remote_user_1 = "@user_aaaaa:remote_server"
+        remote_user_2 = "@user_yyyyy:remote_server"
+        remote_user_3 = "@user_ccccc:remote_server"
+        self._add_user_to_room(room_id, RoomVersions.V1, remote_user_1)
+        self._add_user_to_room(room_id, RoomVersions.V1, remote_user_2)
+        self._add_user_to_room(room_id, RoomVersions.V1, remote_user_3)
+
+        local_users = [local_user_1, local_user_2, local_user_3]
+        remote_users = [remote_user_1, remote_user_2, remote_user_3]
+
+        # The local searching user searches for the term "user", which other users have
+        # in their user id
+        results = self.get_success(
+            self.handler.search_users(searching_user, "user", 20)
+        )["results"]
+        received_user_ids = [result["user_id"] for result in results]
+
+        for user in local_users:
+            self.assertIn(
+                user, received_user_ids, f"Local user {user} not found in results"
+            )
+
+        for user in remote_users:
+            self.assertNotIn(
+                user, received_user_ids, f"Remote user {user} should not be in results"
+            )
+
     def _add_user_to_room(
         self,
         room_id: str,