MSC3958: Suppress notifications from message edits (#3958)

* Suppress message edits.

* Fix typo.

Co-authored-by: Sumner Evans <[email protected]>

* Add @room.

* Match MSC title to PR.

* Add a potential issue.

* Clarify rule placement.

* Change link text.

Co-authored-by: Richard van der Hoff <[email protected]>

* Fix typo.

Co-authored-by: Richard van der Hoff <[email protected]>

* Add a note about mobile clients.

* Update from anoa's feedback.

* Updates for Matrix 1.7

* Update more spec links.

* Minor clarifications.

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

* Add downside about "all messages"

* Clarify again that this *does* work with all messages.

---------

Co-authored-by: Sumner Evans <[email protected]>
Co-authored-by: Richard van der Hoff <[email protected]>
Co-authored-by: Andrew Morgan <[email protected]>

proposals/3958-suppress-notifications-of-message-edits.md

@@ -0,0 +1,142 @@
+# MSC3958: Suppress notifications from message edits
+
+[Event replacement](https://spec.matrix.org/v1.7/client-server-api/#event-replacements)
+(more commonly known as message edits) signals that a message is intended to
+be replaced with new content.
+
+This works well for fixing typos or other minor correction, but can cause
+spurious notifications if the event mentions a user's display name / localpart or
+if it includes `@room` (which is particularly bad in large rooms as every user
+is re-notified). This contributes to notification fatigue as the additional
+notifications contain no new information.
+
+Additionally for users which have a room set to "all messages" then every event
+edit results in an additional notification.[^1]
+
+## Proposal
+
+A new default push rule is added to suppress notifications due to [edits](https://spec.matrix.org/v1.7/client-server-api/#event-replacements).
+
+```json
+{
+    "rule_id": ".m.rule.suppress_edits",
+    "default": true,
+    "enabled": true,
+    "conditions": [
+        {
+            "kind": "event_property_is",
+            "key": "content.m\\.relates_to.rel_type",
+            "value": "m.replace"
+        }
+    ],
+    "actions": []
+}
+```
+
+This rule should be placed after the [`.m.rule.room.server_acl` rule](https://spec.matrix.org/v1.7/client-server-api/#default-override-rules)
+as the last override rule.
+
+It would match events such as those given in [event replacements](https://spec.matrix.org/v1.7/client-server-api/#event-replacements)
+portion of the spec:
+
+```json5
+{
+    "type": "m.room.message",
+    "content": {
+        "body": "* Hello! My name is bar",
+        "msgtype": "m.text",
+        "m.new_content": {
+            "body": "Hello! My name is bar",
+            "msgtype": "m.text"
+        },
+        "m.relates_to": {
+            "rel_type": "m.replace",
+            "event_id": "$some_event_id"
+        }
+    },
+    // ... other fields required by events
+}
+```
+
+With the [updated mentions behavior in Matrix 1.7](https://spec.matrix.org/v1.7/client-server-api/#user-and-room-mentions),
+this would allow the [`.m.rule.is_user_mention`](https://spec.matrix.org/v1.7/client-server-api/#_m_rule_is_user_mention)
+and the [`.m.rule.is_room_mention`](https://spec.matrix.org/v1.7/client-server-api/#_m_rule_is_room_mention)
+rules to continue matching, even for edited events, while suppressing notifications
+from other edits.
+
+Some users may be depending on notifications of edits. If a user would like to
+revert to the old behavior they can disable the `.m.rule.suppress_edits` push rule.
+
+## Potential issues
+
+### Edits of invites and tombstones
+
+The [`.m.rule.invite_for_me` and `.m.rule.tombstone`](https://spec.matrix.org/v1.7/client-server-api/#default-override-rules)
+rules may still cause spurious notifications if events which match those rules
+are edited. Both of those are state events and
+[not subject to valid edits](https://spec.matrix.org/v1.7/client-server-api/#validity-of-replacement-events).
+
+### Keeping notifications up-to-date
+
+Mobile clients currently depend on the push notifications of edited events to update the
+text of on-screen notifications. The proposed push rule would result in mobile clients no
+longer receiving these edits; but showing slightly outdated text on a notification screen. That
+is only a minor impact and it would be better to separate when (& why) we send pushes vs.
+when we generate notifications.
+
+### Suppression of notifications to a new keyword
+
+If an event is edited and the new event (but not the original event) matches a keyword
+then the notification would erroneously be suppressed.
+
+## Alternatives
+
+An alternative solution would be to add a push rule with no actions and a condition to
+check whether a notification was generated for the original message.
+
+This would be placed as an override rule before the `.m.rule.contains_display_name`
+and the `.m.rule.roomnotif` [push rules](https://spec.matrix.org/v1.7/client-server-api/#push-rules).
+
+This would suppress duplicate notifications, while still allow for new notifications due
+to new mentions or keywords changing.
+
+## Security considerations
+
+None forseen.
+
+## Future extensions
+
+If message edits by other senders were allowed than it would be useful to
+know when your own message was edited, but this
+[is not currently allowed](https://spec.matrix.org/v1.7/client-server-api/#validity-of-replacement-events).
+A future MSC to define this behavior should take into account notifying
+users in this situation.
+
+## Unstable prefix
+
+The unstable prefix of `.org.matrix.msc3958.suppress_edits` should be used in place of
+`.m.rule.suppress_edits`.
+
+A previous version of this MSC used `.com.beeper.suppress_edits` with a different condition
+(which should match the same events), but different rule placement.
+
+## Dependencies
+
+N/A
+
+<!-- Footnotes below -->
+
+[^1]: A room can be configured to be notify for "all messages" by creating a [room-specific push rule](https://spec.matrix.org/v1.7/client-server-api/#push-rules)
+with an `rule_id` of the room ID & has `actions` set to "notify" , e.g.:
+
+    ```json
+    {
+        "rule_id" : "!abcdef:example.com",
+        "default" : false,
+        "enabled" : true,
+        "actions" : ["notify"]
+    }
+    ```
+
+    See the [Element Web](https://github.com/matrix-org/matrix-react-sdk/blob/da7aa4055e04f291be9b5141b704bd12aec03d0c/src/RoomNotifs.ts#L162-L170)
+    implementation.