[Tex/LaTex] Row coloring too wide (Pandoc MD -> PDF)

colorlongtablepandoc

I'd like to have zebra striped table rows in the PDF output converted from Markdown using Pandoc. To create Latex tables Pandoc relies on the packages booktabs and longtable. Therefore I tried to redefine the longtable environment. Here's a MWE (Markdown file content): 

---
header-includes:
  - \usepackage[table]{xcolor}
  - \definecolor{lightgray}{gray}{0.95}
  - \let\OldLongtable\longtable
  - \let\OldEndLongtable\endlongtable
  - \renewenvironment{longtable}{\rowcolors{1}{white}{lightgray}\OldLongtable}{\OldEndLongtable}
---

| Right | Left | Default | Center |
|------:|:-----|---------|:------:|
|   12  |  12  |    12   |    12  |
|  123  |  123 |   123   |   123  |
|    1  |    1 |     1   |     1  |

  : Demonstration of pipe table syntax.

The problem now is that the row coloring is wider than the actual table:

enter image description here

How can I fix this?

Edit:
I've stumbled upon some information concerning this issue. The author of a Pandoc Latex Template called Eisvogel states:

Unfortunately the colored cells extend beyond the edge of the table because pandoc uses @-expressions (@{}) like so:

\begin{longtable}[]{@{}ll@{}}
\end{longtable}

Additionally he links to the Latex Wikibook section about @-expressions. But to the Latex novice I am this is all as clear as mud…

Edit 2:
As requested by Zarko here's the same as a complete Latex document (output from Pandoc's Markdown-to-Latex conversion):

\documentclass[]{article}
\usepackage{lmodern}
\usepackage{amssymb,amsmath}
\usepackage{ifxetex,ifluatex}
\usepackage{fixltx2e} % provides \textsubscript
\ifnum 0\ifxetex 1\fi\ifluatex 1\fi=0 % if pdftex
  \usepackage[T1]{fontenc}
  \usepackage[utf8]{inputenc}
\else % if luatex or xelatex
  \ifxetex
    \usepackage{mathspec}
  \else
    \usepackage{fontspec}
  \fi
  \defaultfontfeatures{Ligatures=TeX,Scale=MatchLowercase}
\fi
% use upquote if available, for straight quotes in verbatim environments
\IfFileExists{upquote.sty}{\usepackage{upquote}}{}
% use microtype if available
\IfFileExists{microtype.sty}{%
\usepackage[]{microtype}
\UseMicrotypeSet[protrusion]{basicmath} % disable protrusion for tt fonts
}{}
\PassOptionsToPackage{hyphens}{url} % url is loaded by hyperref
\usepackage[unicode=true]{hyperref}
\hypersetup{
            pdfborder={0 0 0},
            breaklinks=true}
\urlstyle{same}  % don't use monospace font for urls
\usepackage{longtable,booktabs}
% Fix footnotes in tables (requires footnote package)
\IfFileExists{footnote.sty}{\usepackage{footnote}\makesavenoteenv{long table}}{}
\IfFileExists{parskip.sty}{%
\usepackage{parskip}
}{% else
\setlength{\parindent}{0pt}
\setlength{\parskip}{6pt plus 2pt minus 1pt}
}
\setlength{\emergencystretch}{3em}  % prevent overfull lines
\providecommand{\tightlist}{%
  \setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}
\setcounter{secnumdepth}{0}
% Redefines (sub)paragraphs to behave more like sections
\ifx\paragraph\undefined\else
\let\oldparagraph\paragraph
\renewcommand{\paragraph}[1]{\oldparagraph{#1}\mbox{}}
\fi
\ifx\subparagraph\undefined\else
\let\oldsubparagraph\subparagraph
\renewcommand{\subparagraph}[1]{\oldsubparagraph{#1}\mbox{}}
\fi

% set default figure placement to htbp
\makeatletter
\def\fps@figure{htbp}
\makeatother

\usepackage[table]{xcolor}
\definecolor{lightgray}{gray}{0.95}
\let\OldLongtable\longtable
\let\OldEndLongtable\endlongtable
\renewenvironment{longtable}{\rowcolors{1}{white}{lightgray}\OldLongtable}{\OldEndLongtable}

\date{}

\begin{document}

\begin{longtable}[]{@{}rllc@{}}
\caption{Demonstration of pipe table syntax.}\tabularnewline
\toprule
Right & Left & Default & Center\tabularnewline
\midrule
\endfirsthead
\toprule
Right & Left & Default & Center\tabularnewline
\midrule
\endhead
12 & 12 & 12 & 12\tabularnewline
123 & 123 & 123 & 123\tabularnewline
1 & 1 & 1 & 1\tabularnewline
\bottomrule
\end{longtable}

\end{document}

Best Answer

like this:

enter image description here

i extract from yours code minimal working example, where i add code which should solve your problem:

\documentclass{article}
\usepackage[table]{xcolor}
\usepackage{booktabs, longtable}

\begin{document}
\begin{longtable}{@{}   >{\columncolor{white}[0pt][\tabcolsep]}r % <---
                        l
                        l
                        >{\columncolor{white}[\tabcolsep][0pt]}c % <---
                  @{}   }
\caption{Demonstration of pipe table syntax.}\\
    \toprule
Right & Left & Default & Center             \\
    \midrule
\endfirsthead
    \toprule
Right   & Left  & Default   & Center        \\
    \midrule
    \endhead
\rowcolor{gray!10}
12      & 12    & 12        & 12            \\
123     & 123   & 123       & 123           \\
1       & 1     & 1         & 1             \\
\bottomrule
\end{longtable}

\end{document}
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