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, 3 insertions, 2 deletions

diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
index 41ac49fdc8..45c2777117 100644
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -15,6 +15,7 @@
 import logging
 from typing import TYPE_CHECKING
 
+import synapse
 from synapse.api.constants import MAX_DEPTH, EventContentFields, EventTypes, Membership
 from synapse.api.errors import Codes, SynapseError
 from synapse.api.room_versions import EventFormatVersions, RoomVersion
@@ -98,9 +99,9 @@ class FederationBase:
                 )
             return redacted_event
 
-        result = await self.spam_checker.check_event_for_spam(pdu)
+        spam_check = await self.spam_checker.check_event_for_spam(pdu)
 
-        if result:
+        if spam_check is not synapse.spam_checker_api.ALLOW:
             logger.warning("Event contains spam, soft-failing %s", pdu.event_id)
             # we redact (to save disk space) as well as soft-failing (to stop
             # using the event in prev_events).