Consider replacing m.room.aliases with an m.room.alias event listing a single alias

[richvdh]

Currently, the m.room.aliases state event has a state_key corresponding to a given server name, and it lists all the aliases for a given room on that server (or at least, it is intended to). This runs the risk of races when making several changes to the directory at once.

Instead, we could have an m.room.alias event for each alias. For example:

{
    "sender": "@user:foo.com",
    "type": "m.room.alias",
    "state_key": "#sommeliers:foo.com",
    "content": {}
}

(This was originally proposed in matrix-org/matrix-spec-proposals#1130, but I have split it to here to remove redundant content.)

[richvdh]

As pointed out on matrix-org/matrix-spec-proposals#1130: one problem with this is that currently, the matrix protocol doesn't support deleting state (#456). We could instead set an inactive flag in the content, but it would lead to proliferation of redundant state events.

[ara4n]

the whole inactive: true bodge seems okay until we finally support deleting state

[richvdh]

we should also take the opportunity to harden up the validation rules to solve things like https://github.com/matrix-org/matrix-doc/issues/2277.

[KitsuneRal]

m.room.aliases is no more a thing, and we took a different route about the whole thing instead of introducing m.room.alias. Should this be closed-as-not-planned?

[richvdh]

Indeed. MSC2432 removed the special meaning for m.room.aliases.