How to stop a block of code from being parsed?

Question

I would like to pass some latex code to lua directly without it being parsed:

\directlua{
    PrintPrettyLatexCode("LATEX CODE GOES HERE!")
}

BUT latex tries to parse the "LATEX CODE GOES HERE!". I want it to all be treated purely as a string so that the PrintPrettyLatexCode function see's it as a string.

Slashes will need to be double slashed though. I think all that is needed is to parse the code block and make all slashes double before latex parses it(that way macros like \mymacro end up becoming \\mymacro and I think latex will then not try to expand it)

Maybe something like

\directlua{
    PrintPrettyLatexCode(\MakeDoubleSlashes{"LATEX CODE GOES HERE!"})
}

will work if \MakeDoubleSlashes exist?

Answer 1

LuaTeX provides \luaescapestring for escaping characters in Lua strings:

\directlua{
  PrintPrettyLatexCode("\luaescapestring\expandafter{\detokenize{LATEX CODE GOES HERE!}}")
}

Addition

The following defines an environment PrettyPrintLatexCode:

1. The environment contents is written to a temporary file using package filecontents.

2. The file contents is stored in a macro by \CatchFileEdef of package catchfile.
   All characters are read verbatim by using a catcode table, where all slots are set to catcode 12 (other) and the line ends are read as byte 0x10 (\n).

3. The data are passed via \luatexluaescapestring (that is \luaescapestring in LuaLaTeX) to the function PrettyPrintLatexCode.

The full example:

\RequirePackage{filecontents}
\RequirePackage{catchfile}
\RequirePackage{luacode}

\makeatletter
\newcommand*{\PrettyPrint@FileName}{test.file}
\newenvironment*{PrettyPrintLatexCode}{%
  \csname filecontents*\endcsname{\PrettyPrint@FileName}%
}{%
  \csname endfilecontents*\endcsname
  \CatchFileEdef{\PrettyPrint@FileData}{\PrettyPrint@FileName}{%
    \PrettyPrint@CatchSetup
  }%
  \luadirect{%
    PrettyPrintLatexCode("\luatexluaescapestring{\PrettyPrint@FileData}")%
  }%
}
\begingroup
  \lccode`\~=13 %
  \lccode`\9=10 %
\lowercase{\endgroup
  \def\PrettyPrint@CatchSetup{%
    \luatexcatcodetable\CatcodeTableOther
    \endlinechar=13 %
    \catcode13=\active
    \def~{9}%
  }%
}
\makeatother

% Provide a dummy definition for PrettyPrintLatexCode
\luadirect{%
function PrettyPrintLatexCode(str)
  texio.write_nl(
    "*****************************",
    str,
    "*****************************",
    ""
  )
end}

\begin{PrettyPrintLatexCode}
\section{Hello World}

Some text with "double" and 'single' quotes.
  and unmatched (parentheses].

Umlauts: äöüß
\end{PrettyPrintLatexCode}

\stop

Result of the dummy PrettyPrintLatexCode in the terminal/log file:

*****************************
\section{Hello World}

Some text with "double" and 'single' quotes.
  and unmatched (parentheses].

Umlauts: äöüß
*****************************

Answer 2

You could load the luacode package and use \luaexec instead of \directlua:

\luaexec{
    PrintPrettyLatexCode(\MakeDoubleSlashes{"LATEX CODE GOES HERE!"})
}

(This assumes, of course, that PrintPrettyLatexCode is a valid lua function and `MakeDoubleSlashes is a valid TeX macro.) You will still need to prefix a backslash to # and % characters; however, the ~ (tilde) and \\ (double backslash) characters needn't be escaped. To typeset a single backslash, you'll need to use \string\.