[RavSinghChandan]

With the footnotes extra, a footnote that is defined but never referenced still makes markdown2 append the footnotes block, with an empty list:

>>> markdown2.markdown("Text.\n\n[^1]: A note.\n", extras=["footnotes"])
'<p>Text.</p>\n\n<div class="footnotes">\n<hr />\n<ol>\n</ol>\n</div>\n'

_add_footnotes checks self.footnotes (the definitions) but only lists self.footnote_ids (the referenced ones), so the block is empty when nothing is referenced. It now checks the referenced ids, so the output is just <p>Text.</p>. Documents with referenced footnotes are unchanged, and unreferenced definitions were already left out of the list.

Added the footnotes_unreferenced test case

[nicholasserra]

New test missing the html file

[RavSinghChandan]

Thanks, added footnotes_unreferenced.html (and merged master).

[nicholasserra]

@Crozzers Can you think of any reason we'd want to keep a footnote that isn't used anywhere in the text body?

On one hand it's not needed, on another hand if the user inputs a footnote then they might have some reason

[RavSinghChandan]

One detail that may help: this PR doesn't change whether an unused footnote is kept, master already leaves it out. For example, with Text[^a]. and the definitions [^a]: Used. and [^b]: Unused., master lists only a; the text of b is not in the output at all.

The only difference is when no footnote is referenced: master still writes <div class="footnotes"><hr /><ol></ol></div> with nothing in it, which renders as a stray horizontal rule at the end of the page. This PR just skips that empty block.

If you'd rather keep unused footnotes, that would be a separate change to how the list is built, and I'm happy to do it.

[Crozzers]

Explanation makes sense. Can't think of a reason to keep other than if it does draw a stray <hr> then that tells the user they've got dead footnotes they should clean up.
But I think this approach makes more sense