Fragments before document and expectations?

[Omikhleia]

A new user here had its \use and \begin{document} inverted.

In that case, it turns out that the packages don't even seem to be instantiated. (Just quickly checked, with a print in one of the packages init methods, which didn't show up)

The error message is not too helpful. Well, the fix is obvious...

... yet I think that the weird behavior comes from accepting "fragments" (i.e. documents not starting with a \begin{document}), but it's not clear to me if the resulting behavior was really expected 🐱 -- and it's at best confusing. I understand why accepting fragments (i.e. documents not starting with a "document" or "sile" tag) may have an interest in some workflows, but I'd then question what the intended behavior is, when this occur on the very first input fragment. Packages not being loaded at any point without warning is certainly unexpected.

[alerque]

Expected input:

\use[module=packages.color]
\begin{document}
\color[color=red]{Red}
\end{document}

Unexpected input, does not work, should probably give a helpful error:

\use[module=packages.color]
\begin{document}
\color[color=red]{Red}
\end{document}

Unexpected input, works, maybe should not:

\use[module=packages.color]
\color[color=red]{Red}