parskip package causing some problems in parbox itemize content

Question

Here is some simplified content to describe my problem

\documentclass[12pt]{article}
\usepackage[margin = 0.7 in]{geometry}
\usepackage{parskip}


\begin{document}

Some notational items:
\begin{itemize}
    \item Infinite series are referred to only as series.
    \item Dropping the index and infinity symbol from the summation symbol is also possible. i.e $\sum_{n=1}^\infty a_n = \sum a_n$. It also implies starting point of the series is not important. It can begin with $0$, $1$, $3$ or any other number...
    \item Not dropping the index from the summation symbol will occur when the index really does need to be there and cannot be changed

\end{itemize}

\fbox{
\parbox{\textwidth}{
If $\sum a_n$ and $\sum b_n$ are both convergent series then:

\begin{itemize}
    \item sadsads
    \item sdafsdf
\end{itemize}
}
}

\end{document}

I would like to box the contents of the \parbox, but I have realized that the spacing between the text after each bullet, and the spacing between normal text and bulleted lists is different for stuff inside \parbox than it is for stuff outside.

One way to rid myself of this problem is to not import the parskip package. So I know importing it is what causes the weird re-spacing inside the \parbox. However I need to import parskip for other reasons, namely because I don't want to indent my paragraphs in this particular document.

How can I prevent this behavior, and keep my paragraphs non-indented? Perhaps there is a way without importing parskip?

Answer 1

\parbox automatically resets the parskip to 0pt. If you do not want this, you can patch the internal macro to avoid changing \parskip using \patchcmd from etoolbox:

\documentclass[12pt]{article}
\usepackage[margin = 0.7 in]{geometry}
\usepackage{etoolbox}
\usepackage{parskip}
\makeatletter
\patchcmd\@arrayparboxrestore{\parskip}{\@gobble}{}{\undefined}
\makeatother

\begin{document}

Some notational items:
\begin{itemize}
    \item Infinite series are referred to only as series.
    \item Dropping the index and infinity symbol from the summation symbol is also possible. i.e $\sum_{n=1}^\infty a_n = \sum a_n$. It also implies starting point of the series is not important. It can begin with $0$, $1$, $3$ or any other number...
    \item Not dropping the index from the summation symbol will occur when the index really does need to be there and cannot be changed
\end{itemize}

\fbox{
\parbox{\textwidth}{
If $\sum a_n$ and $\sum b_n$ are both convergent series then:

\begin{itemize}
    \item sadsads
    \item sdafsdf
\end{itemize}
}
}

\end{document}

Answer 2

Change some code in the package to restore the \parskip inside the list.

\documentclass[12pt]{article}
\usepackage[margin = 0.7 in]{geometry}
\usepackage{parskip}
\makeatletter

\edef\svparskip{\the\parskip}
\def\@listI{\parskip=\svparskip\relax\leftmargin\leftmargini
   \topsep\z@ \parsep\parskip \itemsep\z@}
\let\@listi\@listI
\@listi

\makeatother
\begin{document}

Some notational items:
\begin{itemize}
    \item Infinite series are referred to only as series.
    \item Dropping the index and infinity symbol from the summation symbol is also possible. i.e $\sum_{n=1}^\infty a_n = \sum a_n$. It also implies starting point of the series is not important. It can begin with $0$, $1$, $3$ or any other number...
    \item Not dropping the index from the summation symbol will occur when the index really does need to be there and cannot be changed

\end{itemize}

\fbox{
\parbox{\textwidth}{
If $\sum a_n$ and $\sum b_n$ are both convergent series then:

\begin{itemize}
    \item sadsads
    \item sdafsdf
\end{itemize}
}
}

\end{document}