[Latex] \today does not do anything

[MuntashirAkon]

Explain the problem.
Latex has a special \today command to print today's date, and it is not outputting anything in the HTML format. This command can be very useful for serving documentations via a CI, for example.

Current workaround is to create a placeholder for a date and replace it with the date generated by other means (e.g. UNIX date).

Pandoc version?

pandoc 2.17.1.1
Compiled with pandoc-types 1.22.1, texmath 0.12.4, skylighting 0.12.2,
citeproc 0.6.0.1, ipynb 0.2

[jgm]

This is by design. Pandoc allows you to include raw LaTeX in markdown, but it gets passed through only to LaTeX, not to HTML, which wouldn't know what to do with it.
You could use a Lua filter to find this bit of raw HTML in the AST and replace it with the date.

[jgm]

Sorry, I assumed your source was markdown, not LaTeX; you didn't say.
If the source is LaTeX, then we could consider parsing \today as a date.

[jgm]

 % pandoc -f latex -t native -s
\date{\today}
Pandoc
  Meta { unMeta = fromList [ ( "date" , MetaInlines [] ) ] }
  []

% pandoc -f latex+raw_tex -t native -s
\date{\today}
Pandoc
  Meta
    { unMeta =
        fromList
          [ ( "date"
            , MetaInlines [ RawInline (Format "latex") "\\today" ]
            )
          ]
    }
  []

[jgm]

We could think about changing the first output above to

Pandoc
  Meta { unMeta = fromList [ ( "date" , MetaInlines [Str "2014-04-04"] ) ] }
  []

Of course there's the question what date format to use. We don't have awareness of localized date formats, so it's probably best just to use something like YYYY-mm-dd, even though this is a bit different from what you'd get in LaTeX.
We have a function in PandocMonad to getZonedTime, so this is feasible.
We could keep the second behavior above in the case where the raw_tex extension is enabled.

[MuntashirAkon]

I think Latex uses dots rather than hyphens. But it's still better than producing nothing at all.

[jgm]

The format LaTeX uses depends on your locale. When I use \today I get "February 10, 2022". Duplicating this locale-dependent behavior is probably too much trouble, though.

[tarleb]

Aside: there's an example in the Lua filters docs that adds a (localized) date: https://pandoc.org/lua-filters.html#setting-the-date-in-the-metadata

[jgm]

We can easily generate a formatted date if we know what format to use. The missing piece is figuring out what format to use, e.g., based on the LOCALE environment variable or the lang metadata field. That's the complexity I'd rather not add.