From 7bb3673f37d02d8bcda586daaac3334aebe81195 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Date: Mon, 6 Sep 2021 14:35:56 +0100
Subject: [PATCH] Ease searching for M_TOO_LARGE-related error codes (#10750)

---
 changelog.d/10750.misc |  1 +
 synapse/event_auth.py  | 15 ++++++---------
 2 files changed, 7 insertions(+), 9 deletions(-)
 create mode 100644 changelog.d/10750.misc

diff --git a/changelog.d/10750.misc b/changelog.d/10750.misc
new file mode 100644
index 0000000000..ded5cf626c
--- /dev/null
+++ b/changelog.d/10750.misc
@@ -0,0 +1 @@
+Refactor event size checking code to simplify searching the codebase for the origins of certain error strings that are occasionally emitted.
\ No newline at end of file
diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index c3a0c10499..b63a1afe93 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -216,21 +216,18 @@ def check(
 
 
 def _check_size_limits(event: EventBase) -> None:
-    def too_big(field):
-        raise EventSizeError("%s too large" % (field,))
-
     if len(event.user_id) > 255:
-        too_big("user_id")
+        raise EventSizeError("'user_id' too large")
     if len(event.room_id) > 255:
-        too_big("room_id")
+        raise EventSizeError("'room_id' too large")
     if event.is_state() and len(event.state_key) > 255:
-        too_big("state_key")
+        raise EventSizeError("'state_key' too large")
     if len(event.type) > 255:
-        too_big("type")
+        raise EventSizeError("'type' too large")
     if len(event.event_id) > 255:
-        too_big("event_id")
+        raise EventSizeError("'event_id' too large")
     if len(encode_canonical_json(event.get_pdu_json())) > MAX_PDU_SIZE:
-        too_big("event")
+        raise EventSizeError("event too large")
 
 
 def _can_federate(event: EventBase, auth_events: StateMap[EventBase]) -> bool: