Mrthfx

this query is related to How to pass an optional argument to an environment with verbatim content? (whose solution did not work in my case) and with Emulating @ifnextchar in expl3 (which is the one I'm trying to adapt).

I have defined an environment (listcontent) using xparse which encapsulates filecontentdef (which is verbatim plus macro) using the argument !O{} and key = val which works well if ALWAYS pass the optional argument.

My idea is to be able to write the environment without having to use an empty optional argument [], this is where I am lost, I have read the documentation of peek_meaning:NF but I do not understand it at all (the catcodes is confusing for me).

It works correctly if I use it in the following way:

begin{listcontents}[]

begin{listcontents}[key=val]

begin{listcontents}[

                    key=val

                    ]

and I would like to do it in the following way

begin{listcontents}

begin{listcontents}

[not key = value, only a bracket whit text]

that is, if you do not find [key = val] right after }, insert a line ending ^^M and [not key = value, only a bracket whit text] would be recorded by the environment.

This is my sample file:

documentclass{article}

usepackage{fancyvrb,filecontentsdef,xparse}

begin{document}

makeatletter



ExplSyntaxOn

keys_define:nn { listcontents }

  {

    save-env   .tl_set:N         = l_env_save_tl,

    save-env   .initial:n        = content,

    show-env   .bool_set:N       = l_env_show_tl,

    show-env   .initial:n        = true,

    name-tmp   .tl_set:N         = l_tmp_name_tl,

    name-tmp   .initial:n        = jobname.tsc,

    save-macro .bool_set:N       = l_save_macro_tl,

    save-macro .initial:n        = true,

  }



NewDocumentEnvironment{ listcontents }{ !O{} }

  {

  group_begin:

  IfNoValueF { #1 } { keys_set:nn { listcontents } { #1 } }

  %peek_meaning_ignore_spaces:NF [ { char_set_catcode_active:N ^^M char_set_catcode_end_line:N ^^M  \ }

  %peek_meaning:NF c_space_tl { char_set_catcode_active:N ^^M char_set_catcode_end_line:N ^^M  ^^M  }

  deffilecontentsdef {@tempswafalsefilec@ntentsdef}%

   filecontentsdef{ l_tmp_name_tl }{ l_tmpa_tl }

   }

  {

  endfilecontentsdef

  group_end:

  group_begin:

  IfNoValueF { #1 } { keys_set:nn { listcontents } { #1 } }

  IfBooleanT{ l_env_show_tl } { filecontentsexecl_tmpa_tl }

  group_end:

  }

ExplSyntaxOff

makeatother

section{Correct}

begin{listcontents}[show-env=true]

This is correct, use:

% some comented lines

begin{verbatim}

begin{listcontents}[show-env=true]

end{verbatim}

end{listcontents}



The textbf{file generate} is:

VerbatimInput[frame=single,numbers=left,numbersep=3pt]{jobname.tsc} par



begin{listcontents}[

                    show-env=true

                    ]

This is correct, use:

% some comented lines

begin{verbatim*}

begin{listcontents}[

                    show-env=true

                    ]

end{verbatim*}

end{listcontents}



The textbf{file generate} is:



VerbatimInput[frame=single,numbers=left,numbersep=3pt]{jobname.tsc} par





begin{listcontents}[]

This is correct, use empty []:

% some comented lines

begin{verbatim*}

begin{listcontents}[]

end{verbatim*}

end{listcontents}



The textbf{file generate} is:

VerbatimInput[frame=single,numbers=left,numbersep=3pt]{jobname.tsc} par



section{No Correct}

begin{listcontents} [NO optional argument]

This is correct for key=val , use space before [] :

% some comented lines

begin{verbatim*}

begin{listcontents} [NO optional argument]

end{verbatim*}

but verb*+[NO optional argument]+ its not save in macro

and the space between the letters has disappeared.

end{listcontents}



The textbf{file generate} is:

VerbatimInput[frame=single,numbers=left,numbersep=3pt]{jobname.tsc} par



begin{listcontents}

This is what I want to happen when I omit []

% some comented lines

begin{verbatim*}

begin{listcontents}

This is what I want to happen when I omit []

% some comented lines

end{verbatim*}

but verb*+[NO optional argument]+ its not save in macro

and space between the letters and first line has disappeared.

end{listcontents}



The textbf{file generate} is:

VerbatimInput[frame=single,numbers=left,numbersep=3pt]{jobname.tsc}



end{document}

Can this be done using xparse/expl3?

regards