Deleting a room leaves clients with stuck rooms

[matrixbot]

This issue has been migrated from #16001.

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When a room is deleted through start_shutdown_and_purge_room (e.g. using the admin API), the users in the room don't receive a leave event or any other signal that it should be removed from the room list.

This leaves clients with stuck rooms that cannot have messages sent into. When that happens, the issue can only be fixed manually by the user: the user has to 'Clear cache and reload' (or equivalent).

Noticed as at Synapse v1.88.0 (though I have heard this issue mentioned earlier too; older Synapse-dev discussion)

[benkuly]

What is the current state of this issue? As a developer of a Matrix SDK (Trixnity) I don't want to build inefficient workarounds for homeserver implementations, that sort of violate the spec.

And if this is not going to be fixed, the behavior should at least be mentioned in the snapse admin API docs. Maybe with an recommendation, how a client could find out efficiently, that the room does not exists anymore.