The recent change that uses a separate button has the problem of not knowing how wide the widget would be (I am not sure if that was the case earlier too).
! From a previous comment
The only thing I dislike about this patterns that its never clear how much space the widget is taking…
This is more of a problem when the widget is in a dialog:
I don't know how to fix this. Making .oo-ui-selectFileWidget-label an inline-block with a max-width of 100% doesn't help. Will we have to specify an absolute em value? If yes, what?