Enumerate in tabular creates unwanted vertical space

Question

Consider

\documentclass{article}
\usepackage{enumitem}

\begin{document}

\begin{tabular}{l p{4cm}}
    Head & Content\\
    \hline
    Foo &
    \begin{enumerate}[label={\textbf{\arabic*.}}, itemindent=0pt, leftmargin=*, nosep]
        \item A
        \item B
    \end{enumerate}
    \\
    \hline
\end{tabular}

\end{document}

which produces unwanted vertical space before and after the list:

However adding surrounding text renders as expected:

\begin{tabular}{l p{4cm}}
    Head & Content\\
    \hline
    Foo &
    How does
    \begin{enumerate}[label={\textbf{\arabic*.}}, itemindent=0pt, leftmargin=*, nosep]
        \item A
        \item B
    \end{enumerate}
    this work?
    \\
    \hline
\end{tabular}

Answer 1

Maybe it's simpler to define a variant of enumerate for use in tables, with specific parameters. I borrowed the \compress command from an answer on this site: it makes latex believe the list is at the very beginning of a minipage, so latex adds no vertical spacing before lists.

I also used the rules from booktabs, which have some vertical padding, and a variable thickness.

\documentclass{article}
\usepackage{enumitem}
\newlist{tabenum}{enumerate}{1}
\setlist[tabenum]{label=\arabic*. ,wide=0pt, leftmargin=*, nosep, itemsep=2pt, font = \bfseries, after=\vspace{-\baselineskip}, before=\compress}
\usepackage{array, booktabs}
\makeatletter
\newcommand*{\compress}{\@minipagetrue}
\makeatother

\begin{document}

\begin{tabular}{l p{4cm}}
    Head & Content\\
    \midrule
    Foo &
    \begin{tabenum}
        \item A. Some text some text some text
        \item B
    \end{tabenum}
    \\
    \bottomrule
\end{tabular}

\end{document} 

Answer 2

You can use the before and after options in order to adjust the space before and after the list to your needs:

\documentclass{article}
\usepackage{enumitem}

\begin{document}

\begin{tabular}{l p{4cm}}
    Head & Content\\
    \hline
    Foo &
    \begin{enumerate}[label={\textbf{\arabic*.}}, itemindent=0pt, leftmargin=*, nosep,after=\vspace{-\baselineskip},before=\vspace{-0.5\baselineskip}]
        \item A
        \item B
    \end{enumerate}
    \\
    \hline
\end{tabular}

\end{document}