matrix-spec-proposals/proposals/4053-mentions-mixin.md

MSC4053: Extensible Events - Mentions mixin

Matrix 1.7 introduced "intentional mentions" to improve how users are mentioned via Matrix events. This was defined in MSC3952, which deprecated the legacy push rules, but left it to a future MSC to disable them:

• .m.rule.contains_display_name
• .m.rule.contains_user_name
• .m.rule.roomnotif

The logical time to remove these legacy mentions push rules is when extensible events are supported.

Proposal

It is proposed that a future room version implementing MSC3932 shall stop supporting the above legacy mentions rules. This does not require any changes as noted in MSC3932:

Push rules which don't specify a room_version_supports condition are assumed to not support extensible events and are therefore expected to be treated as disabled when a room version does support extensible events.

Intentional mentions (i.e. the m.mentions property) is redefined as an extensible events "mixin" (see MSC1767). No changes to the implementation are needed except for additional push rules (similar to those defined in MSC3933) ¹:

The .m.rule.mixin.is_user_mention override push rule would appear directly before the .m.rule.is_user_mention push rule:

{
    "rule_id": ".m.rule.mixin.is_user_mention",
    "default": true,
    "enabled": true,
    "conditions": [
        {
            "kind": "event_property_contains",
            "key": "content.m\\.mentions.user_ids",
            "value": "[the user's Matrix ID]"
        },
        {
            "kind": "room_version_supports",
            "feature": "m.extensible_events"
        }
    ],
    "actions": [
        "notify",
        {
            "set_tweak": "sound",
            "value": "default"
        },
        {
            "set_tweak": "highlight"
        }
    ]
}

(Note: \\. would become a single logical backslash followed by a dot since the above is in JSON-representation. See the appendicies.)

The .m.rule.mixin.is_room_mention override push rule would appear directly before the .m.rule.is_room_mention push rule:

{
    "rule_id": ".m.rule.mixin.is_room_mention",
    "default": true,
    "enabled": true,
    "conditions": [
        {
            "kind": "event_property_is",
            "key": "content.m\\.mentions.room",
            "value": true
        },
        {
            "kind": "sender_notification_permission",
            "key": "room"
        },
        {
            "kind": "room_version_supports",
            "feature": "m.extensible_events"
        }
    ],
    "actions": [
        "notify",
        {
            "set_tweak": "highlight"
        }
    ]
}

Potential issues

This does not really allow for the removal of the old push rules (until implementations drop support for legacy room versions), but it is a step in the correct direction.

Alternatives

An additional feature could be defined which allows for use both with and without extensible events.

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This could potentially be grouped into MSC3932 or MSC3933 if desired.

Security considerations

Additional push rules result in extra processing, but an implementation could partition push rules by room version.

Unstable prefix

While this proposal is not considered stable, implementations should use org.matrix.msc4053.* in place of m.*. Also note that the kind and feature flags may need to use unstable identifiers until MSC3931 and MSC3932 are merged.

Dependencies

This MSC builds on the following MSCs which at the time of writing have not yet been accepted into the spec:

• MSC3931: Push rule condition for room version features
• MSC3932: Extensible events room version push rule feature flag

It also depends on the following MSCs which at the time of writing have been accepted into the spec, but not yet released:

• MSC1767: Extensible event types & fallback in Matrix (v2)

It also depends on the following MSCs which at the time of writing have been accepted into the spec and released:

• MSC3952: Intentional Mentions

The following MSCs are related and may help understanding of this MSC, but not dependencies:

• MSC3933: Core push rules for Extensible Events
• MSC3955: Extensible Events - Automated event mixin (notices)

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1. Note the proposed push rules are identical to the push rules from MSC3952, except the rule ID is updated and they include a room_version_supports condition. ↩︎