Possible spec violation? m.room.message with empty content field

[hugecheese]

When doing my initial /sync from the https://matrix.org homeserver, I got back the following event:

{
  "content": {},
  "event_id": "$BPPs0MTfE4y-8F58bmvITRM7rz4YATGtOvBcQhPBWaY",
  "origin_server_ts": 1571015847357,
  "sender": "@bowdown097:matrix.org",
  "type": "m.room.message",
  "unsigned": {
    "age": 513533411,
    "redacted_because": {
      "content": {},
      "event_id": "$QjO7JJsn_KmuudfkpSLr-TYOT7BuemfwzsbsIuI5qtc",
      "origin_server_ts": 1571016502195,
      "redacts": "$BPPs0MTfE4y-8F58bmvITRM7rz4YATGtOvBcQhPBWaY",
      "sender": "@bowdown097:matrix.org",
      "type": "m.room.redaction",
      "unsigned": {
        "age": 512878573
      }
    },
    "redacted_by": "$QjO7JJsn_KmuudfkpSLr-TYOT7BuemfwzsbsIuI5qtc"
  }
}

The spec states that any event with the type m.room.message must always have the body and msgtype fields.

[turt2live]

The event was redacted, so this is expected.

[hugecheese]

@turt2live I see, but why aren't the fields marked as optional? If they might not be present because of a redaction, then I don't think they should be marked as Required

[turt2live]

That's where the spec is a bit unclear: I believe the theory is that the fields are required to send, but not receive. A redaction affects the event in ways after it has been sent, so it naturally can force the event to lose otherwise required fields.

In practice, implementations should be resilient to malformed event contents.