Uniformize spam-checker API: github/ts/spam-errors ts/spam-errors

- Some callbacks should return `True` to allow, `False` to deny, while others should return `True` to deny and `False` to allow. With this PR, all callbacks return `ALLOW` to allow or a `Codes` (typically `Codes.FORBIDDEN`) to deny.
- Similarly, some methods returned `True` to allow, `False` to deny, while others returned `True` to deny and `False` to allow. They now all return `ALLOW` to allow or a `Codes` to deny.
- Spam-checker implementations may now return an explicit code, e.g. to differentiate between "User account has been suspended" (which is in practice required by law in some countries, including UK) and "This message looks like spam".

1 files changed, 12 insertions, 5 deletions

diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py

index 33d827a45b..fbbb667cd4 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -16,6 +16,7 @@ import logging
 import string
 from typing import TYPE_CHECKING, Iterable, List, Optional
 
+import synapse
 from synapse.api.constants import MAX_ALIAS_LENGTH, EventTypes
 from synapse.api.errors import (
     AuthError,
@@ -137,10 +138,13 @@ class DirectoryHandler:
                         403, "You must be in the room to create an alias for it"
                     )
 
-            if not await self.spam_checker.user_may_create_room_alias(
+            spam_check = await self.spam_checker.user_may_create_room_alias(
                 user_id, room_alias
-            ):
-                raise AuthError(403, "This user is not permitted to create this alias")
+            )
+            if spam_check is not synapse.spam_checker_api.ALLOW:
+                raise AuthError(
+                    403, "This alias creation request has been rejected", spam_check
+                )
 
             if not self.config.roomdirectory.is_alias_creation_allowed(
                 user_id, room_id, room_alias_str
@@ -426,9 +430,12 @@ class DirectoryHandler:
         """
         user_id = requester.user.to_string()
 
-        if not await self.spam_checker.user_may_publish_room(user_id, room_id):
+        spam_check = await self.spam_checker.user_may_publish_room(user_id, room_id)
+        if spam_check is not synapse.spam_checker_api.ALLOW:
             raise AuthError(
-                403, "This user is not permitted to publish rooms to the room list"
+                403,
+                "This request to publish a room to the room list has been rejected",
+                spam_check,
             )
 
         if requester.is_guest: