debug changes

[rgrinberg]

@copy could you try reproducing the issue with this PR?

You need to set the log file with an environment variable: OCAMLLSP_DEBUG_CHANGES=ocamllsp.log. Then, just reproduce the bug and paste the first change set that introduces the incorrect document.

[ulugbekna]

I can reproduce but seemingly not if I rebase onto #1005

I have a suspicion that we may be changing the document in the store with an older version of it.

I also made a bit of changes to this PR here https://github.com/ocaml/ocaml-lsp/tree/debug_changes_ulugbek

[ulugbekna]

I also think that when auto-save is on, we try sending in a task_if_running diagnostics a lot more often, it could be possible that we compute diagnostics for a version of document that's older than the one in doc store?

[rgrinberg]

I also think that when auto-save is on, we try sending in a task_if_running diagnostics a lot more often, it could be possible that we compute diagnostics for a version of document that's older than the one in doc store?

I don't think it would matter. An additional save in the end would fix the situation with the diagnostics. While @copy was telling us that doing additional saves at the end does not change anything.

[rgrinberg]

the bug is fixed