I find in Lua filters that I sometimes would like to know whether or not I'm in a footnote. Currently, I'm trying to move punctuation before footnotes. Given my citation style, I know that a Cite in body text will produce a footnote, while a Cite in a footnote will not. So I want to move punctuation before a Cite when it's not in a footnote. Since a filter function for Inlines will descend into footnotes as well, there doesn't seem to be any way to tell when the Cite is in a footnote.

In this particular case, I can work around the limitation because any Cite in a footnote will either be the first element or will have a Space before it. So with that assumption, I can look for the last innermost element before the Cite and check its type: if it's a Str,  can append the punctuation to it and delete the punctuation from where it was. if it's a Space, I do nothing, because I must be in a footnote. However, at least in the long term, I'd like to be able to tell whether or not I'm in a footnote.