\IfInstanceExistTF undefined with -dev formats

[muzimuzhi]

Originally reported by @akiyks in CTeX-org/ctex-kit#707.

Commands \IfInstanceExist(TF) are always undefined with -dev formats which have templates integrated, both with and without xtemplate package.

\documentclass{article}
\usepackage{xtemplate}

\show\IfInstanceExistTF

\begin{document}
\end{document}

gives

pdflatex:
> \IfInstanceExistTF=\long macro:
#1#2->\__xtemplate_if_instance_exist:nnnTF {#1}{}{#2}.

pdflatex-dev:
> \IfInstanceExistTF=undefined.

• Compiled with non-dev format, templates are not integrated into LaTeX2e kernel, thus loading xtemplate loads the frozen version xtemplate-2023-10-10.sty, in which \IfInstanceExist(TF) are provided.
• Compiled with -dev format, templates are integrated thus loading xtemplate only adds commands \DeclareRestrictedTemplate and \DeclareObjectType.

Though the LaTeX2e kernel doesn't need \IfInstanceExist(TF), I think they should be available if xtemplate package is explicitly loaded.

The docs of \IfInstanceExist(TF) in xtemplate.dtx were first dropped then restored in 0599924 (Revert "Drop \IfInstanceExist(TF) docs", 2024-02-15), but not their implementation.

Related PRs

• Templates #1335
• Integrate templates into LaTeX kernel latex2e#1132

[muzimuzhi]

Ah, \IfInstanceExist(TF) were reintroduced to the kernel in commit latex3/latex2e@41f33bc4 (Re-introduce \IfInstanceExist(TF), 2024-02-15). It's just not included in any public nor dev releases.

[muzimuzhi]

I filed a new issue in latex3/latex2e: latex3/latex2e#1306 to suggest a new pre-release.