learn-cmd-syntax.sty

\usepackage{xparse}
\ExplSyntaxOn
% By egreg, http://tex.stackexchange.com/questions/40404/parsing-latex-to-output-number-of-arguments-for-each-command-defined
%
% Defining commands like this
%   \newcommand{\xaa}{abc}
%   \newcommand*{\xab}[1]{abc}
%   \newcommand{\xac}[2][cccc]{abc}
%   \renewcommand{\phi}{\varphi}
%   \newenvironment{xad}{}{}
%   \newenvironment{xae}[1]{}{}
%   \newenvironment{xaf}[2][sss]{}{}
% results in this output in myfile.cmd:
%   command,\xaa ,0,0,
%   command,\xab *,1,0,
%   command,\xac ,1,1,cccc
%   command,\phi ,0,0,
%   environment,xad,0,0,
%   environment,xae,1,0,
%   environment,xaf,1,1,sss
% The fields in the output are:
%   (command|environment),name,n-required-args,n-optional-args,default
% Extraneous whitespace occurs in <name> and should be filtered out.
%
% Define the command that will start the working; we'll redefine \newcommand
% so that \newcommand{\xac}[2][cccc]{abc} will execute
%
%    \command_check:w { \command_check_newcommand:w }{ command } {\xab} 
%
% #1 = \newcommand|\renewcommand|\newenvironment|\renewenvironment (in new form)
% #2 = command|environment
% #3 = the possible *
% #4 = the argument to \newcommand
% #5 = the number of arguments
% #6 = the possible optional argument
% 
% We check if the last argument is missing and take the appropriate action 
\NewDocumentCommand{ \command_check:w }{m m s m O{0} o}
  {
   \IfBooleanTF{#3}
     { \tl_gset:Nn \g_command_check_star_tl { * } \bool_gset_true:N \g_command_check_star_bool }
     { \tl_gset:Nn \g_command_check_star_tl { } \bool_gset_false:N \g_command_check_star_bool }
   \IfNoValueTF{#6}
     { \command_check_noopt:nnnn {#1} {#2} {#4} {#5} }
     { \command_check_opt:nnnnn {#1} {#2} {#4} {#5} {#6} }
  }
% \StartSaveCommands sets up the checks, first by creating aliases for the kernel commands
% and then redefining them as explained above
\NewDocumentCommand{\StartSaveCommands}{}
  {
   \cs_set_eq:NN \command_check_newcommand:w \newcommand
   \cs_set_eq:NN \command_check_renewcommand:w \renewcommand
   \cs_set_eq:NN \command_check_newenvironment:w \newenvironment
   \cs_set_eq:NN \command_check_renewenvironment:w \renewenvironment
   \cs_set:Npn \newcommand { \command_check:w {\command_check_newcommand:w}{command} }
   \cs_set:Npn \renewcommand { \command_check:w {\command_check_renewcommand:w}{command} }
   \cs_set:Npn \newenvironment { \command_check:w {\command_check_newenvironment:w}{environment} }
   \cs_set:Npn \renewenvironment { \command_check:w {\command_check_renewenvironment:w}{environment} }
  }
% \StopSaveCommands restores the kernel commands
\NewDocumentCommand{\StopSaveCommands}{}
  {
   \cs_set_eq:NN \newcommand \command_check_newcommand:w
   \cs_set_eq:NN \renewcommand \command_check_renewcommand:w
   \cs_set_eq:NN \newenvironment \command_check_newenvironment:w 
   \cs_set_eq:NN \renewenvironment \command_check_renewenvironment:w
  }
% \WriteSaveCommands will take care of writing out the list of commands
% with their number of arguments
\NewDocumentCommand{\WriteSaveCommands}{}
  {
   \iow_open:Nn \g_command_check_write { \jobname.cmd }
   \seq_map_inline:Nn \g_command_check_seq {\iow_now:Nx \g_command_check_write { ##1 } }
  }
% Allocate a write stream
\iow_new:N \g_command_check_write
% If there's no optional argument, say \newcommand{\xab}[1]{aaa},
% we want to write out "command,\xab ,1,0", so we store that
% string into an item appended to the sequence \g_command_check_seq
\cs_new:Npn \command_check_noopt:nnnn #1 #2 #3 #4
  {
   \seq_gput_right:Nx \g_command_check_seq
     {
      #2 , 
      \tl_to_str:n{#3}\bool_if:NT\g_command_check_star_bool{*}
      , #4, 0,
     }
   \exp_after:wN #1 \g_command_check_star_tl {#3} [#4]
  }
% If there's an optional argument, say \newcommand{\xac}[2][cccc]{abc},
% we want to write out "command,\xac,1,1[cccc]; everything as before,
% but we decrease by 1 the number of stated arguments
\cs_new:Npn \command_check_opt:nnnnn #1 #2 #3 #4 #5
  { 
   \seq_gput_right:Nx \g_command_check_seq
     {
      #2 \bool_if:NT \g_command_check_star_bool {*}, \tl_to_str:n {#3} , 
      \int_to_arabic:n {#4-1} , 1,\tl_to_str:n{#5}
     }
   \exp_after:wN #1 \g_command_check_star_tl {#3}[#4][#5]
  }
% Allocate the sequence, the token list variable and the boolean
\seq_new:N \g_command_check_seq
\tl_new:N \g_command_check_star_tl
\bool_new:N \g_command_check_star_bool
\ExplSyntaxOff