Lsp-mode: We should forget diagnostics after file is modified

[yyoncho]

not doing that is causing stale diagnostics until the new one are received.

[innerout]

I have been tackling on this behavior lately with ccls and I need to make an extra modification in the buffer and then save it to make the errors disappear. I think if this is solved it will greatly improve the experience of flycheck users.

[yyoncho]

I have been tackling on this behavior lately with ccls and I need to make an extra modification in the buffer and then save it to make the errors disappear. I think if this is solved it will greatly improve the experience of flycheck users.

This should not happen with the latest lsp-mode. The errors should either disappear after 0.5 seconds after modification or 0.5 after they are received from the server. Unless you have removed on idle from flycheck.

[innerout]

How can I verify the state of flycheck's on idle option you mention? Is there an lsp-mode option that could possibly disable it?

[yyoncho]

Check if flycheck-check-syntax-automatically has idle-change. Also, doing M-x flycheck-buffer will force lsp-mode to report the latest error reported from the server.

[innerout]

You were right, in my configuration I had the snippet below and after removing it everything works as it should.
elisp (setq flycheck-check-syntax-automatically '(mode-enabled save))

[yyoncho]

I will take a look.

[scturtle]

Check if flycheck-check-syntax-automatically has idle-change.

https://github.com/emacs-lsp/lsp-mode/blob/92b3b75268a602dcc02f8eec1c333f4551f09539/lsp-mode.el#L8290-L8293

Why idle-change must be checked here? There are users like me wish to see diagnostics only after saved.

[yyoncho]

Check if flycheck-check-syntax-automatically has idle-change.

https://github.com/emacs-lsp/lsp-mode/blob/92b3b75268a602dcc02f8eec1c333f4551f09539/lsp-mode.el#L8290-L8293

Why idle-change must be checked here? There are users like me wish to see diagnostics only after saved.

That is why this check is here - do not refresh diagnostics on idle if on idle is not on. But indeed, there is a bug here. We should also update the diagnostics if the buffer is saved and user wants to update diags on save. This is what is causing your issues.