Get Failed to load timeline position when click on The conversation continues here

[JeanPaulLucien]

Steps to reproduce

I was in room for a long time.

Room title is ruhaskell/meetup
Room address is #gitter_ruhaskell=2Fmeetup:matrix.org

Room has got the status "The room has been replaced..." in the past. I found the link #ruhaskell_meetup:gitter.im in the messages of the room. I clicked to it and have joined to room successfully. Then I clicked on "... continues here" (link: https://matrix.to/#/#ruHaskell_meetup:gitter.im)

Outcome

What did you expect?

Not that.

What happened instead?

Popup:

Failed to load timeline position

Tried to load a specific point in this room's timeline, but you do not have permission to view the message in question.

Console:

GET https://matrix-client.matrix.org/_matrix/client/r0/rooms/!jjkaaCVlXjzyslmmSJ%3Agitter.im/context/%24n1FjwdNlY2rGeHU0LK41G6CPRwOyjGbhRov7Wx0c25o?filter=%7B%22lazy_load_members%22%3Atrue%7D 403
fetch @ fetch.ts:62
Error loading timeline panel at !jjkaaCVlXjzyslmmSJ:gitter.im/$n1FjwdNlY2rGeHU0LK41G6CPRwOyjGbhRov7Wx0c25o M_FORBIDDEN: MatrixError: [403] You don't have permission to access that event. (https://matrix-client.matrix.org/_matrix/client/r0/rooms/!jjkaaCVlXjzyslmmSJ%3Agitter.im/context/%24n1FjwdNlY2rGeHU0LK41G6CPRwOyjGbhRov7Wx0c25o?filter=%7B%22lazy_load_members%22%3Atrue%7D)
    at c (vector://vector/webapp/bundles/.../vendors~init.js:2:1430935)
    at p.requestOtherUrl (vector://vector/webapp/bundles/.../vendors~init.js:2:3548382)

Operating system

Windows

Application version

1.11.23

How did you install the app?

In-app update

Homeserver

matrix.org

Will you send logs?

No

[t3chguy]

You don't have permission to access that event.

The issue is one of history permissions which isn't something the client can do anything to get around

@MadLittleMods could this possibly be the migration thing not setting the appropriate history visibility for the target of the tombstone?

[MadLittleMods]

I'm not sure what room that the #gitter_ruhaskell=2Fmeetup:matrix.org alias points to as it doesn't work now.

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Joining #ruHaskell_meetup:gitter.im works as expected for me and lands me at !jjkaaCVlXjzyslmmSJ:gitter.im

History visibility (m.room.history_visibility) is set to world_readable for all public Gitter rooms.

The event in the 403 /context error, $n1FjwdNlY2rGeHU0LK41G6CPRwOyjGbhRov7Wx0c25o, is the m.room.create event in the room, so it definitely should be available/visible no matter what.

Doing /join https://matrix.to/#/!jjkaaCVlXjzyslmmSJ:gitter.im/$n1FjwdNlY2rGeHU0LK41G6CPRwOyjGbhRov7Wx0c25o?via=matrix.org (or using gitter.im via server) to mimic the request reproduces the problem (404/403 on /context). Seems like a Synapse issue? And I'm guessing Element picks the m.room.create event to continue reading from since it's the earliest event in the room.

[MadLittleMods]

It looks like this is a duplicate of #1230

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Doing /join https://matrix.to/#/!jjkaaCVlXjzyslmmSJ:gitter.im/$n1FjwdNlY2rGeHU0LK41G6CPRwOyjGbhRov7Wx0c25o?via=matrix.org (or using gitter.im via server) to mimic the request reproduces the problem (404/403 on /context). Seems like a Synapse issue? And I'm guessing Element picks the m.room.create event to continue reading from since it's the earliest event in the room.

In Synapse, given that we're in the gitter.im room, the matrix.org server knows about the m.room.create event for the state/auth chain. But it's probably just listed as an "outlier" which won't be returned for /event or /context.

It looks like this is just a case where matrix.org doesn't have the m.room.create event and the client /event and /context endpoints don't ask over federation to backfill it. Here are the issues tracking that problem:

• /context does not try to backfill unknown events from federation. matrix-org/synapse#3848
• /event does not try to backfill unknown events from federation matrix-org/synapse#15263
• The other thing that could help here is forwards fill on /messages since we could call /messages?dir=f and it would just work to pull the earliest messages in the room. (needs an MSC, related Load messages after the given day matrix-org/matrix-viewer#72)

This issue is probably better closed in favor of those issues but it does not to discount the fact that this is a really awful user experience.