Spacing issue at start of minipage (and similar)

[FrankMittelbach]

Brief outline of the bug

There is a long-known issue that TeX drops spaces (and penalties) at the start of a vertical list (such as generated by minipage) but only if that list ist totaly empty. Things that produce invisible "whatsits" like color change that state and therefore a minipage starting with, say, a list, suddenly sees some vertical space at the top coming from \parskip being added and not dropped by TeX.

Minimal example showing the bug

\RequirePackage{latexbug}       % <--should be always the first line (see CONTRIBUTING)!
\documentclass{article}

\usepackage{hyperref,color}   % sample other code can have the same effect

\begin{document}

\fbox{%
  \begin{minipage}{10cm}%       % no issue
  \begin{itemize}
    \item abc \par xyz
  \end{itemize}
  \end{minipage}%
}

\fbox{%
  \begin{minipage}{10cm}% 
  \LinkTargetOff               % no issue if anchor/dest is suppressed
  \begin{enumerate}
    \item abc \par xyz
  \end{enumerate}
  \end{minipage}%
}

\fbox{%
  \begin{minipage}{10cm}%
  \begin{enumerate}
    \item abc\label{b} \par xyz   % hyperref backref is the issue
  \end{enumerate}
  \end{minipage}%
}

\fbox{%
  \begin{minipage}{10cm}%
  \color{red}                  % color is the issue
  \begin{enumerate}
    \item abc \par xyz
  \end{enumerate}
  \end{minipage}%
}

\end{document}

first two boxes show extra spacing.

With the new paragraph handling it should be possible to catch this finally.

[mrpiggi]

I am just curious, if this also addresses the issue with \addvspace (#307)?

[FrankMittelbach]

I am just curious, if this also addresses the issue with \addvspace (#307)?

no it doesn't. It only deals with an extra \parskip added at the top of a vertical box, but this is a place where you can't necessarily avoid placing something like \color. The issue in (#307) is related but also different.

[mrpiggi]

Thanks for your response and clarification