Users can see sidebars they don't belong to - in chats they belong to. They should still record messages for those sidebars.
We should instead check if the thread is present in the users store.

Is this is correct for sidebars?

Should we set the unread status?

When we leave a thread we should also leave its sidebars. But it can happen that we don't have all the sidebars in our store while leaving the thread.

One solution could be to iterate through every sidebar here and leave them one by one, but it is still a fragile solution. An alternative is to leave only the thread from the operation. Then, someone who generates operations is responsible for generating all the necessary ones.

We're deleting only non-sidebar threads and sidebars without a parent. If a sidebar doesn't have a parent, it means that its parent was deleted in the past.

Updated the logic

Created a comment with it https://linear.app/comm/issue/ENG-8923/generate-and-process-dmoperations-in-components#comment-aa034d1b.

But it can happen that we don't have all the sidebars in our store while leaving the thread.

In what scenarios might this occur? Would it occur because the user joined the parent chat after the sidebar was created? Or something else?

This could happen when an update about creating a sidebar was received after the user tried to leave the thread.

Got it. It seems like in all of these cases (the one I proposed and the one you proposed), it is safe to discard the update