Automating processing of trailing punctuation (if any) for hyperlinks

Question

This is a follow-up to Should Hyperlinks include trailing puctuation as part of the link text?, and this question is about automating the processing of the trailing character. I would like to be able to have the punctuation be specified after the macro as in:

\CreateLink{<linke style>}{<link target>}{<link text>},

where I have used a comma as an example. I prefer the above instead of:

\CreateLink{<linke style>}{<link target>}{<link text>,}

for two reasons:

1. It is more readable (punctuation is more obvious in the code).
2. Allows me to defer the decision of the weather to include the punctuation as part of the link text or not.

So, I would like to modify the \CreateLink macro to be able to check if the subsequent character is a space or not. If not, then consider the next character as punctuation and include that character in the output of \CreateLink.

I realize that the solution will probably involve \@ifnextchar but I was not able able to get that to work. In the attempt below I output a - if a non-space character is found. Since the - is in the output for all cases, my attempt is clearly missing something.

References:

• Check if next char is {

Code:

% The following \def allows to have one version of this code for this questions,
% and the previous question at:
% 
%    https://tex.stackexchange.com/questions/125357/should-hyperlinks-include-trailing-puctuation-as-part-of-the-link-text
%
\def\SmartVersion{}%  Should be uncommented for this question.

\documentclass{article}
\usepackage{xparse}
\usepackage{xcolor}
\usepackage{soul}
\usepackage{xstring}
\usepackage{xspace}
\usepackage[colorlinks=true]{hyperref}

%% ----------------------------------------------------------------
%%                https://tex.stackexchange.com/questions/36894/
%%                    underline-omitting-the-descenders
%%
%%
\makeatletter
\ExplSyntaxOn
    \cs_new:Npn \white_text:n #1
      {
        \fp_set:Nn \l_tmpa_fp {.01}
        \fp_mul:Nn \l_tmpa_fp {#1}
        \llap{\textcolor{white}{\the\SOUL@syllable}\hspace{\fp_to_decimal:N \l_tmpa_fp em}}
        \llap{\textcolor{white}{\the\SOUL@syllable}\hspace{-\fp_to_decimal:N \l_tmpa_fp em}}
      }
    \NewDocumentCommand{\whiten}{ m }
        {
          \int_step_function:nnnN {1}{1}{#1} \white_text:n
        }
\ExplSyntaxOff

\NewDocumentCommand{ \varul }{ D<>{5} O{0.2ex} O{0.1ex} +m } {%
\begingroup
\setul{#2}{#3}%
\def\SOUL@uleverysyllable{%
   \setbox0=\hbox{\the\SOUL@syllable}%
   \ifdim\dp0>\z@
      \SOUL@ulunderline{\phantom{\the\SOUL@syllable}}%
      \whiten{#1}%
      \llap{%
        \the\SOUL@syllable
        \SOUL@setkern\SOUL@charkern
      }%
   \else
       \SOUL@ulunderline{%
         \the\SOUL@syllable
         \SOUL@setkern\SOUL@charkern
       }%
   \fi}%
    \ul{#4}%
\endgroup
}%
\makeatother
%% ----------------------------------------------------------------

\newcommand{\CreateLinkA}[2]{%
    \hypersetup{pdfborder={0 0 1}, urlcolor=.}%
    \href{#1}{#2}%
}%
\newcommand{\CreateLinkB}[2]{%
    \hypersetup{pdfborder={0 0 0}, urlcolor=red}%
    \href{#1}{#2}%
}%
\newcommand{\CreateLinkC}[2]{%
    \hypersetup{colorlinks=false,urlcolor=.}%
    \setulcolor{blue}%
    \href{#1}{\varul[0.5pt][1.0pt]{#2}}%
}%

\makeatletter
\newcommand{\CreateLink}[3]{%
    \IfStrEqCase{#1}{%
        {1}{\CreateLinkA{#2}{#3}}%
        {2}{\CreateLinkB{#2}{#3}}%
        {3}{\CreateLinkC{#2}{#3}}%
    }%
    \ifdefined\SmartVersion% 
        % If the next character is anything other than a space, 
        % include that char as part of the text. 
        % The "-" is supposed to whatever the next character is,
        % but don't know how to get that character.  
        % Note that the "-" is shown in all cases, so this is NOT working.
        \@ifnextchar{\space}{\space}{-}%
    \else% "ELSE" clause is unused in this question
        \xspace%
    \fi
}%
\makeatother


\begin{document}
\textbf{Punctuation NOT part of link:}\medskip
\par Go and check out \CreateLink{1}{www.yahoo.com}{the yahoo}, and also\ldots
\par Go and check out \CreateLink{2}{www.yahoo.com}{the yahoo}, and also\ldots
\par Go and check out \CreateLink{3}{www.yahoo.com}{the yahoo}, and also\ldots

\bigskip
\textbf{Punctuation part of link:}\medskip
\par Go and check out \CreateLink{1}{www.yahoo.com}{the yahoo,} and also\ldots
\par Go and check out \CreateLink{2}{www.yahoo.com}{the yahoo,} and also\ldots
\par Go and check out \CreateLink{3}{www.yahoo.com}{the yahoo,} and also\ldots
\end{document}

Answer 1

Here is a try.

The following code only uses your first link style as the different styles didn't seem to be essential for the question. It uses the packages etoolbox for its list processing tools and its \ifblank macro, and Heiko Oberdiek's ltxcmds for its \ltx@ifnextchar that allows for checking a following space via \ltx@ifnextchar{ }{<true>}{<false>}.

The \CreateLink{<address>}{<text>} macro below checks if a space follows. If not the next token is taken and it is checked if it is in a list of tokens that is set with \setlinkpunctuation{<punctuation marks>}. This macro gives you full control which punctuation mark should be included in the link.

We get:

\documentclass{article}
\usepackage{xcolor}
\usepackage{etoolbox,ltxcmds}
\usepackage[colorlinks=true]{hyperref}

\makeatletter
% list parser with no separator:
\DeclareListParser*\@add@punctuation{}
% set the punctuation list (the parser does not like blank lists):
\def\setlinkpunctuation#1{%
  \def\@punctuation{}%
  \ifblank{#1}
    {}
    {\@add@punctuation{\listadd\@punctuation}{#1}}%
}

% check if a space follows; if yes, only create the link, else
% eat the next token:
\newcommand*\CreateLink[2]{%
  \ltx@ifnextchar{ }
    {\@create@link{#1}{#2}{}}
    {\@create@link{#1}{#2}}%
}

% check if #3 is among the punctuation marks
% and either place it inside the link or outside:
\def\@create@link#1#2#3{%
  \ifinlist{#3}{\@punctuation}
    {\@create@actual@link{#1}{#2#3}}
    {\@create@actual@link{#1}{#2}#3}%
}

% the actual link:
\def\@create@actual@link#1#2{%
  \hypersetup{pdfborder={0 0 1}, urlcolor=.}%
  \href{#1}{#2}%
}
\makeatother

\begin{document}

only \texttt{,}\par\medskip
\setlinkpunctuation{,}
Go and check out \CreateLink{www.yahoo.com}{the yahoo}, and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo} and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo}. and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo}! and also\ldots\par

\bigskip
nothing\par\medskip
\setlinkpunctuation{}
Go and check out \CreateLink{www.yahoo.com}{the yahoo}, and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo} and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo}. and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo}! and also\ldots\par

\bigskip
\texttt{,.} and \texttt{!}\par\medskip
\setlinkpunctuation{.,!}
Go and check out \CreateLink{www.yahoo.com}{the yahoo}, and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo} and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo}. and also\ldots\par
Go and check out \CreateLink{www.yahoo.com}{the yahoo}! and also\ldots\par

\end{document}