We don't provide enough info in invites to unnamed rooms to name them correctly in clients.

[ara4n]

If you:

• create a private room (e.g. a DM)
• invite someone to it
• their client will show an invite that says "Matthew invited you to chat", rather than showing the correct synthetic name of the room (e.g. "Matthew and Amandine and 5 others").

We should provide sufficient state in the invite event for the target client to correctly synthesise the right name.

If this needs a spec change, then i'd expect one to be filed alongside fixing this in synapse.

This is a major UX shortcoming - refiled from element-hq/element-meta#379

[clokep]

By default we send (as matching the spec):

synapse/synapse/config/api.py

Lines 118 to 128 in 4586119

	_DEFAULT_PREJOIN_STATE_TYPES = [
	EventTypes.JoinRules,
	EventTypes.CanonicalAlias,
	EventTypes.RoomAvatar,
	EventTypes.RoomEncryption,
	EventTypes.Name,
	# Per MSC1772.
	EventTypes.Create,
	# Per MSC3173.
	EventTypes.Topic,
	]

We would probably need to ensure enough information is sent for a client to run a similar algorithm to our calculate_room_name, that means we're likely missing:

• m.room.canonical_alias
• Information that this is a DM (or that there's only a single other user)