xsimverb: \l_xsim_file_begin_tl is never expanded since v0.20

[muzimuzhi]

The following example in package manual, Appendix C was broken by commit 5239682, since the argument of \XSIMsetfilebegin, which is then stored in \l_xsim_file_begin_tl, was never expanded before written to a temp file.

xsim/doc/xsim-manual.tex

Lines 2368 to 2393 in 899c94c

	\documentclass{article}
	\usepackage{xsimverb,listings}
	\makeatletter
	\NewDocumentEnvironment{example}{o}
	{%
	\XSIMsetfilebegin{\@percentchar\space file `\jobname.tmp'}%
	\XSIMsetfileend{\@percentchar\space bye bye}%
	\IfNoValueTF{#1}
	{\XSIMfilewritestart*{\jobname.tmp}}
	{\XSIMfilewritestart{\jobname.tmp}}%
	}
	{%
	\XSIMfilewritestop
	\lstinputlisting[language={[LaTeX]TeX}]{\jobname.tmp}%
	\input{\jobname.tmp}
	}
	\makeatother
	\begin{document}
	\begin{example}
	bla bla \LaTeX
	\end{example}
	\end{document}

To be consistent with the usages of \l_xsim_file_(begin/end)_tl in xsim itself, one possible proposal could be

diff --git a/code/xsimverb.sty b/code/xsimverb.sty
index 2945542..e8ea801 100644
--- a/code/xsimverb.sty
+++ b/code/xsimverb.sty
@@ -294,10 +294,10 @@
   { \xsim_file_write_stop: }

 \NewDocumentCommand \XSIMsetfilebegin {+m}
-  { \tl_set:Nn \l_xsim_file_begin_tl {#1} }
+  { \tl_set:Nx \l_xsim_file_begin_tl {#1} }

 \NewDocumentCommand \XSIMsetfileend {+m}
-  { \tl_set:Nn \l_xsim_file_end_tl {#1} }
+  { \tl_set:Nx \l_xsim_file_end_tl {#1} }

 \NewDocumentCommand \XSIMgobblechars {m}
   { \int_set:Nn \l_xsim_line_gobble_int {#1} }

[cgnieder]

Thanks. Fixed by introducing variants that expand their argument first.