Hi,
I've found it useful in some situations to expand all custom LaTeX macros (such as `\newcommand{\Curl}{\nabla\times}`, for example) in a document before rendering it.
For example, with Quarto being used to produce a book in both pdf and html formats, the macros stored in a file `_macros.tex` are processed differently in the LaTeX path (simply including `_macros.tex` in the preamble) and in the Html version (where Mathjax needs to be given such macros for every page that it renders; it doesn't work to provide it once for the whole book/website).
An alternative that sounds quite robust would be to run something like de-macro (
https://www.ctan.org/tex-archive/support/de-macro) on the source document before it is rendered: the macros are still used for convenience of writing in the input file, but they get expanded explicitly before LaTeX or Mathjax is asked to render.
Unfortunately, de-macro is a Python script, and might be a little fragile as it processes whole documents with regex. I wonder if achieving the same thing would be easier with a Lua filter in pandoc? Presumably, having already all the equations isolated in the AST makes life a bit easier, and I believe there is already a mechanism in pandoc to process and expand `\newcommand` directives for non-latex output. Is this mechanism available to a Lua filter that could be used in a Quarto workflow?
Many thanks,
baptiste