chemnum: label-format not affecting \cmpd definition globally?

Question

When compiling the code

\documentclass{article}
\usepackage{chemnum}
\begin{document}

\cmpd*[label-format=\bfseries\textsuperscript,pre-label-code=\textbf{Me\textsubscript{2}L}]{Me2bdc}
\resetcmpd[1]
\cmpd*[label-format=\bfseries\textsuperscript,pre-label-code=\textbf{H\textsubscript{2}L}]{H2bdc}

\cmpd{Me2bdc} and \cmpd{H2bdc}

\cmpd[format=\bfseries\textsuperscript]{Me2bdc} and \cmpd[format=\bfseries\textsuperscript]{H2bdc}

\end{document}

using pdflatex, the following will be rendered:

where the second line represents what was intended here.

According to the chemnum manual, label-format should be used to alter a label's property, while format is used where the display of individual instances of \cmpd is to be altered locally. However, the definition of label-format=\bfseries\textsuperscript seems to have no effect on the diplay of 1 (see first line). Only when format=\bfseries\textsuperscript is used during calling the respective compound, the formatting will take place (second line). What am I getting wrong here? Using chemnum 1.2c from an up-to-date TeX Live 2019.

Answer 1

This is a misinterpretation or misunderstanding of the manual.

label-format is a property of a compound but not an option which can be set. Compound properties cannot be set directly by a user.

The option is called format and acts globally when used with \setchemnum and locally when used as option to \cmpd.

So the answer is: use \setchemnum{format=\bfseries\textsuperscript}.

If you want to restrict this to only a few compounds you either need to set the format again after declaring the compounds or use a group: this works because option setting is local to grouping but compounds are always defined globally.

\documentclass{article}
\usepackage{chemnum}

\begin{document}

\begingroup
\setchemnum{format=\bfseries\textsuperscript}
\cmpd*[pre-label-code=\textbf{Me\textsubscript{2}L}]{Me2bdc}
\resetcmpd
\cmpd*[pre-label-code=\textbf{H\textsubscript{2}L}]{H2bdc}
\endgroup

\cmpd{Me2bdc} and \cmpd{H2bdc}

\end{document}

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It might be reasonable to be able to set the property label-format compoundwise when the the label is declared. For this an option would probably be useful (and it could be called label-format). If this sounds like a useful feature to you please feel free to open a feature request on github.