Synctex: make it work with environment accessing its content (e.g. environ or xparse +b option)

Question

If I create an environment using environ and \BODY or xparse and +b, the synctex functionality breaks: instead of going to the appropriate line, it goes at the end of the environment. I guess that the fact that \BODY is put into a macro disturbs LaTeX, but I'm curious to know if I can solve it somehow (eventually in lualatex)

MWE

\documentclass[]{article}
\usepackage{environ}% http://ctan.org/pkg/environ
%% The +b is needed because in real life the text may be moved to another file
\NewDocumentEnvironment{testSynctex}{s+b}{
  \IfBooleanTF{#1}{}{#2}%
}{}
\NewEnviron{testSynctexEnviron}{%
  \BODY
}
\begin{document}
\section{xparse}
\begin{testSynctex}
  This
is
a
long
text
try
to synctex
me !
\end{testSynctex}
\section{xparse*}
\begin{testSynctex}*
  This
text
  should
be
hidden
\end{testSynctex}
\section{environ}
\begin{testSynctexEnviron}
  This
is
a
long
text
try
to synctex
me !
\end{testSynctexEnviron}
\end{document}

EDIT

The solution proposed by user202729 works nicely for the above MWE (and it definitely answers part of my question and will surely turn out to be useful if I can't find a more generalizable answer). However, here is another MWE that I'd like to solve where the solution proposed by user202729 does not work anymore:

I'm duplicating a text between two sections (by writing first the content to a file before inputting that file). Unfortunately, this breaks synctex: not only for the copied text (it goes to the dummy file instead of the main file), but also for the initial text (it goes to the end of the environment).

Would it be possible to make synctex work at least for the text in the first section? And if you can make it work also for the text in the second section… it would be awesome.

MWE:

\documentclass{article}
\def\nameOfFile{mydummyfile.tex}
%% Write to a file
\newwrite\appendwrite
\NewDocumentCommand\writetofile{m+m}{%
  %% Open the file
  \immediate\openout\appendwrite #1\relax%
  %% Write the text to the file
  \immediate\write\appendwrite{#2}%
  %% Close the file
  \immediate\closeout\appendwrite%
}
\NewDocumentEnvironment{duplicateContentKeepSynctex}{+b}{%
  #1%
  \writetofile{\nameOfFile}{#1}%
}{}
\begin{document}
\section{Main body}
\begin{duplicateContentKeepSynctex}
  This content is duplicated to another section.
However synctex does not work in both sections.
Ideally I'd love to make synctex work in both sections (in such a way that it always links to the main file, NOT mydummyfile).
But I guess it's impossible.
But at least, is it possible to make it work for the first section?
\end{duplicateContentKeepSynctex}
\section{Duplicated section}
\input{\nameOfFile}
\end{document}

Answer 1

I don't see how that would be possible in a macro expansion language. The content of a macro is not processed so you can only get error messages or synctex markers where it is used and that may be nowhere near the defintion. In these cases the internal macro saving the environment body happens to be used close to the definition so the synctex data is close to the source but to tex your example is like

\def\abc{
some text
XXX
that gets saved here
}
multiple pages of arbitrary document source
\abc

and you are asking that synctex associates XXX with line 4 in the middle of the definition of \abc not with a line "multiple pages later" where \abc gets used.

Answer 2

Alright, the solution.

If compiles with lualatex both sections will have synctex preserved, otherwise only the first section will be.

%! TEX program = pdflatex
\documentclass{article}
\usepackage{saveenv}
\usepackage{currfile}
\usepackage{rescansync}
\ExplSyntaxOn
\NewDocumentEnvironment{duplicateContentKeepSynctex}{}{%
  \rescansyncSaveenvghostPacked \savedcontent
}{
  \endrescansyncSaveenvghostPacked
}
\ExplSyntaxOff
\begin{document}
\section{Main body}
\begin{duplicateContentKeepSynctex}
  This content is duplicated to another section.
However synctex does not work in both sections.
Ideally I'd love to make synctex work in both sections (in such a way that it always links to the main file, NOT mydummyfile).
But I guess it's impossible.
But at least, is it possible to make it work for the first section?
\end{duplicateContentKeepSynctex}
\section{Duplicated section}
\rescansyncPacked \savedcontent
\end{document}

It doesn't actually write the content to a file, the content is stored in \savedcontent in some peculiar format that the user isn't supposed to touch. If the user wants to manipulate the content manually, use the programmatic API of rescansync package.

Note

• packages not on CTAN Package is now on CTAN: https://ctan.org/pkg/rescansync . There's package documentation there.