Peeking a room over federation without previews allowed spins forever & cannot join

[jryans]

If I try to peek a room over federation without previews allowed, Riot hangs with a spinner:

Looking at network traffic, there is an initialSync request that fails with 403 Forbidden:

GET /_matrix/client/r0/rooms/<room_id>/initialSync?limit=20

HTTP/2 403 Forbidden

{
    "errcode":"M_FORBIDDEN",
    "error":"User <mxid> not in room <room_id>, and room previews are disabled"
}

[jryans]

The particular room I tried to join has in room state:

"join_rule": "public",
"guest_access": "can_join",
"history_visibility": "world_readable",

[jryans]

I suppose the fundamental issue is that we don't support peeking over federation today, but hopefully matrix-org/matrix-spec-proposals#2444 will help at a protocol level.

We can still do a lot more here in the client to convey the current error state.

[turt2live]

This used to work just fine in Riot, counting it as a regression.

[ara4n]

The problem is worse though - not only does the peek never load, it sounds like there's no option to join? So this means that clicking on any room link over federation is currently broken, which is a pretty spectacular regression.

[turt2live]

Hmm... this seems to be working fine for me:

even with the 403.

[turt2live]

Caused by matrix-org/synapse#6992 - will fix anyways.