Markdown footnotes are duplicated

[lkiesow]

If you add multiple references to one footnote in Markdown like this:

This is a sentence [^fn] with footnote.

This is another sentence [^fn] with footnote.

[^fn]: This is the footnote.

pandoc will create multiple footnotes instead of referencing only one. For example, if converted into Markdown again, one would end up with:

This is a sentence[^1] with footnote.

This is another sentence [^2] with footnote.

[^1]: This is the footnote.

[^2]: This is the footnote.

The same happens when converted to HTML (I didn't try other formats). Obviously, this should not happen but instead it should be one footnote which is just linked to multiple points in the text.

I've tested this locally using version 1.12.3.3 as well as with 1.13.1 at Try pandoc!

[van-de-bugger]

I confirm the bug.

Just to compare: Another markdown processor, multimarkdown, when processing from md to html, generates many references to one footnote.

[mpickering]

It would probably be better to present a uniform solution which works across all output formats.

[lkiesow]

I guess to have a uniform solution is never a bad idea, but I'm woundering which format supports footnotes, but not multiple references to one footnote?

[mpickering]

I have no idea to be honest. That might be a good argument to just apply this change to the markdown writer.

[van-de-bugger]

Why the issue is marked as "enhancement"? I would say it is a bug.

[jgm]

+++ Václav Haisman [Jan 04 16 07:16 ]:

What about using the solution described in
[1]http://tex.stackexchange.com/a/262956/28495?

If we did make a change allowing multiple references
to a single footnote, I'd probably implement it in
LaTeX without relying on an external package like fixfoot,
to keep down dependencies.

But one thing to keep in mind is that pandoc supports many
output formats, not just LaTeX. Any changes in how
footnotes are handled require changes in all of them.

[van-de-bugger]

It seems this issue has a long history and discussion thread I am not aware of. Moreover, I am not experienced in this area, but…

mpickering wrote:

It would probably be better to present a uniform solution which works across all output formats.

I would not agree with this. Output formats differ, and uniform solution may not (or even will not) work for all.

For example: HTML output format assumes one (probably long) page. All the footnotes are printed at the very bottom. And having a separate footnote for every link looks ugly. (Backlinks is not a problem, at least conceptually, look at Mediawiki/Wikipedia solution: they have multiple backlinks in a single footnote.)

Another output format (TeX?) may assume output document consist of multiple pages, and footnotes are printed at the bottom of page. In such a case, it is natural to print footnote on each page containing a reference.

So, internal representation (I am not aware how you call it, probably AST?) should be able to represent multiple links to the same footnote. Each writer (html, tex, etc) should be able to handle it: either generate single footnote or multiple footnotes, depending on output format; no uniform solution is needed.

[claudiosousa]

Any progress on this whatsoever?