Need expl3 package

[BertrandSim]

Hi there, I tried using the subfiles package with a minimal example, but it seems that the subfiles package uses the \ExplSyntaxOn and \ExplSyntaxOff commands, both of which are from the expl3 package.

Without including expl3, I get an error, which from the log file, points to line 30 of subfiles.sty, containing \ExplSyntaxOn command described earlier.

While including the line \usepackage{expl3} in the preamble is a workaround, I'm wondering if it can be fixed, so that I do not have to specify that line explicitly in the main document.

FYI, I'm running MikTex 2.9, vimtex, latexmk, subfiles v2.2, import v6.2

Here are the relevant files in the minimal example:

% main.tex
\documentclass{report}

% \usepackage{expl3}
% including the expl3 package fixes the error 
%   of undefined control sequence in subfiles.sty:30 --> \ExplSyntaxOn

\usepackage{subfiles}

\begin{document}
\tableofcontents
\subfile{chapter1.tex}
\end{document}

%chapter1.tex
\documentclass[main.tex]{subfiles}

\begin{document}

\chapter{Intro}
\label{ch:intro}
Here comes some text

\end{document}

[gsalzer]

Thanks for your report. I see three ways to solve the problem:

• Upgrade LaTeX to a recent version. Since Oct 1, \ExplSyntaxOn is part of LaTeX, so the problem should go away.
• Downgrade subfiles to version 2.0 (available from here).
• Wait an undetermined amount of time until the next release. My plan for this release is to resolve the incompatibility with make4ht in a way that makes subfiles also compatible with old versions of LaTeX.

[BertrandSim]

Well it turns out my MikTeX version is rather old. I decided to go with your first option and yes, updating MikTeX fixed the issue. Feel free to close this issue.

Thank you for your help. I appreciate it!