room directory does not make it clear how to find a resident server

[richvdh]

Link to problem area:

https://spec.matrix.org/v1.5/server-server-api/#get_matrixfederationv1publicrooms
https://spec.matrix.org/v1.5/client-server-api/#get_matrixclientv3publicrooms

Issue

Neither the C-S nor federation /publicRooms APIs make it clear if servers may return rooms that they are no longer resident in (or cannot handle a join request for some other reason).

If servers can return rooms that they are no longer resident in, how is the client supposed to join the room, given there is no server list?

[MTRNord]

Related: should servers not able to help with joining still return that room in their roomlist?

[richvdh]

Related: should servers not able to help with joining still return that room in their roomlist?

I don't really follow how that is different from what I said?

[MTRNord]

Related: should servers not able to help with joining still return that room in their roomlist?

I don't really follow how that is different from what I said?

Ah I think I miss understood yours. I read yours as questioning if there should be some way to tell clients that it is published but they need another server to join via. As in not hiding it server side but telling clients that it doesn't work. So I just misread it apparently. Sorry :)

[KitsuneRal]

Would that (telling the clients how to join) amount to adding via to the fields returned in the public rooms chunk?

[richvdh]

Would that (telling the clients how to join) amount to adding via to the fields returned in the public rooms chunk?

Probably. Though I'm not entirely sure if a server should be returning rooms it cannot handle in its room directory anyway.

[richvdh]

To make a concrete proposal: I assert that:

• Both /_matrix/federation/v1/publicRooms, and /_matrix/client/v3/publicRooms with an empty server, should return only rooms where the server has at least one joined member.
• When calling /join based on the results of a /_matrix/client/v3/publicRooms call, clients should provide a via parameter matching the server parameter used with /publicRooms, if any.

If anyone would like to write that into a proper MSC, I'd be much obliged.