Preventing LaTeX inter-sentence spacing in citations/citeproc

[frabjous]

Consider the following minimal document:

A philosopher once fell off a ladder [@tlp, §6.54].

A philosopher once fell off a ladder (Wittgenstein 1922, sec.\ 6.54).

---
references:
- type: book
  author:
    - family: Wittgenstein
      given: Ludwig
  id: tlp
  issued: 1922
  publisher: Routledge
  publisher-place: London
  title: Tractatus logico-philosophicus
---

Compile with this command (using the pdflatex engine), using the default CSL file, or any other that converts "§" to "sec.".

pandoc file.md -o file.pdf --citeproc

In the output, you'll see that the first line is ever so slightly longer than the second, because there is more space between "sec." and "6.54" in the first. LaTeX by default puts more space between sentences, and is wrongly treating the period in "sec." as if it ended a sentence.

This happens with most abbreviations CSL uses, not just sec. but ch. (for chapters), pp. (if enabled in the style, etc.)

I can't for the life of me figure out how to prevent this. None of these work, i.e., they all still yield the extra space:

• [@tlp, sec. 6.54]
• [@tlp, sec.\ 6.54]
• [@tlp, sec. 6.54] (Unicode non-breaking space U+00A0)

Is there a way to prevent this? Should there be? I realize citeproc is a general tool, not specifically aimed at LaTeX-based output, but since pandoc's PDF conversions do use LaTeX by default, this is a constant annoyance. (Though I admit I'm fussier than most.)

I'm using pandoc 3.8.3 on archlinux if that matters.

[jgm]

One approach is to use \frenchspacing in your LaTeX template. That removes the distinction between sentence-ending and other spacing. It may not be the fix you're looking for, though.

For a very similar issue, see #11279
The suggestion there is to use --natbib or --biblatex, but then you can't use CSL styles or non-bibtex bibliographies.

I am also picky about this sort of thing, so it would be good to solve it.

[jgm]

Another workaround you could try: [@tlp, {}sec.\ 6.54]. The {} will be interpreted as locator, leaving the rest as a suffix that will be passed through literally. This means that you won't get the sorts of treatment citeproc usually gives to locators ("sec." will come through verbatim, there won't be collapsing of page numbers, etc.), but this may be okay for your purposes.

[jgm]

Here's a bit from typical CSL file, apa.csl:

  <macro name="citation-locator">
    <!-- Abbreviate page and paragraph, leave other locator labels in long form, cf. Rule 8.13 -->
    <group delimiter=" ">
      <choose>
        <if locator="page paragraph" match="any">
          <label variable="locator" form="short"/>
        </if>
        <else>
          <label variable="locator" text-case="capitalize-first"/>
        </else>
      </choose>
      <text variable="locator"/>
    </group>
  </macro>

Here you have the "label" ("sec.") and the the locator (the number). Where does the space come from? it comes from the delimiter, which is specified on the group element as " ". It may be that if you put a unicode nonbreaking space here, like "&x160;" you'd get the result you want. Worth a try. To find the relevant part of your CSL file, search for variable="locator".

[jgm]

Tried it. This approach works well, if you know what to modify in the csl file!

[jgm]

Another approach that may work is adding a zero-width joiner to the end of each label (section, volume, etc.) in <terms>. For a sketch of this, see #11279. PERIOD + ZWJ + SPACE does not produce a sentence space with xelatex/lualatex.

[frabjous]

Thanks for your quick replies!

I have \frenchspacing inside the definition of the CSLReferences LaTeX environment in my template to prevent the same problem in the bibliography, but I'd prefer if possible to keep nonfrenchspacing active in my body text, where the citations are, as I do think it looks nice to have the extra space when it is actually between sentences.

I do like the idea of changing the CSL file to use a different delimiter, such as a non-breaking space, as I wouldn't want the line broken there in any output format anyway. I'll try implementing that soon.

Still, it doesn't feel like a complete solution, depending on the use-case. Half the point of using pandoc markdown and CSL references is to make it really easy to switch output formats and citation styles. I'm not going manually edit every CSL file of the ~10,000 in their repo. Similarly, I'd prefer not to put things into the document that would make it incompatible with changing to a different style with different abbreviations, or to use solutions only compatible with xelatex/lualatex instead of pdflatex. Still, a partial workaround is better than nothing!