Remove space when argument is empty in bespoke citation command

Question

I am trying to define a bespoke citation command which mimics the behaviour of \citep[][]{} but for the case when I am using some citation alias, e.g. when the author is an institution and I want its acronym.

The problem I have is that, when there is no text after the citation, Latex is still displaying a space between the year and the closing parenthesis. I have tried defining a \checkEmpty command based on this post but to no avail.

My code is below:

\documentclass{article}
\usepackage[]{natbib}
\usepackage[colorlinks=true,allcolors=blue]{hyperref}
\defcitealias{BCBS2011}{BCBS}
\newcommand{\checkEmpty}[1]{
    \if\relax\detokenize{#1}\relax{\ignorespaces}\else{#1}\fi
}
\newcommand{\mycitepalias}[3]{
    \citepalias[#2][\citeyear{#1}\checkEmpty{#3}]{#1}
}
\begin{document}
\noindent%
\mycitepalias{BCBS2011}{}{}\
\mycitepalias{BCBS2011}{with text before}{}\
\mycitepalias{BCBS2011}{with text before}{and after}
\bibliography{bibliography.bib}
\end{document}

The output is displayed below. As you can see in the first and second line, there is an undesirable space.

PS: As a bonus, I would like to add a comma after the date in case there is text after the citation.

Answer 1

Your {\ignorespaces} does nothing, because \ignorespaces is anyway followed by }. But it's irrelevant nonetheless.

You are adding spaces by not protecting endlines.

\begin{filecontents*}{\jobname.bib}
@misc{BCBS2011,
  author={{Basel Committee on Bank Supervision}},
  title={Basel {III}: {A} global regulatory framework for
         more resilient banks and banking system},
  year=2011,
}
\end{filecontents*}
\documentclass{article}
\usepackage[]{natbib}
\usepackage[colorlinks=true,allcolors=blue]{hyperref}
\defcitealias{BCBS2011}{BCBS}
\newcommand{\checkEmpty}[1]{%
  \if\relax\detokenize{#1}\relax
  \else
    \ #1%
  \fi
}
\newcommand{\mycitepalias}[3]{%
    \citepalias[#2][\citeyear{#1}\checkEmpty{#3}]{#1}%
}
\begin{document}
\mycitepalias{BCBS2011}{}{}
\mycitepalias{BCBS2011}{with text before}{}
\mycitepalias{BCBS2011}{with text before}{and after}
\bibliographystyle{plainnat}
\bibliography{\jobname}
\end{document}