Negate the effect of parskip on \item

Question

I have a tex file:

\documentclass{report}
\usepackage{enumitem,parskip}

\setlist[enumerate]{wide=\parindent}
\setlist[enumerate,2]{labelindent=2\parindent}

\begin{document}

Generally, it extends the idea of the derivative from realvalued functions of one real variable to functions on normed spaces.

The Fréchet derivative should be contrasted to the more general Gateaux derivative which is a generalization of the classical directional derivative.

\begin{enumerate}

  \item Generally, it extends the idea of the derivative from realvalued functions of one real variable to functions on normed spaces.

  \item The Fréchet derivative should be contrasted to the more general Gateaux derivative which is a generalization of the classical directional derivative.

The Fréchet derivative should be contrasted to the more general Gateaux derivative which is a generalization of the classical directional derivative.

\begin{enumerate}

  \item Generally, it extends the idea of the derivative from realvalued functions of one real variable to functions on normed spaces.
  
  \item The Fréchet derivative should be contrasted to the more general Gateaux derivative which is a generalization of the classical directional derivative.  

\end{enumerate}

\end{enumerate}

\end{document}

Can we nullify the effect of parskip on the paragraph starting with \item?

Answer 1

Since parskip sets \parindent to zero, specifying itemindent=\parindent sets the item indent to zero.

Define your own length parameter for the job.

\documentclass{report}
\usepackage{enumitem,parskip}

\newlength{\enumerateindent}
\setlength{\enumerateindent}{20pt}% <--- adjust to your taste
\setlist[enumerate]{wide=\enumerateindent}
\setlist[enumerate,2]{labelindent=2\enumerateindent}

\begin{document}

Generally, it extends the idea of the derivative from realvalued functions 
of one real variable to functions on normed spaces.

The Fréchet derivative should be contrasted to the more general Gateaux 
derivative which is a generalization of the classical directional derivative.

\begin{enumerate}

\item Generally, it extends the idea of the derivative from realvalued 
  functions of one real variable to functions on normed spaces.

\item The Fréchet derivative should be contrasted to the more general
  Gateaux derivative which is a generalization of the classical
  directional derivative.

The Fréchet derivative should be contrasted to the more general Gateaux
derivative which is a generalization of the classical directional derivative.

\begin{enumerate}

\item Generally, it extends the idea of the derivative from realvalued
  functions of one real variable to functions on normed spaces.
  
\item The Fréchet derivative should be contrasted to the more general
  Gateaux derivative which is a generalization of the classical
  directional derivative.  

\end{enumerate}

\end{enumerate}

\end{document}

I personally find this kind of typesetting very confusing for the reader. For instance, the paragraph before the inner enumerate seems to stop the outer enumerate.

Answer 2

From the documentation of enumitem, the option wide=\parindent is equivalent to

align=left, leftmargin=0pt, labelindent=\parindent,
listparindent=\parindent, labelwidth=0pt, itemindent=!

As such, one solution is

\setlist[enumerate]{align=left, leftmargin=0pt, labelindent=15pt, labelwidth=0pt, itemindent=!}
\setlist[enumerate,2]{labelindent=30pt}

A MWE

\documentclass{report}
\usepackage{enumitem,parskip}


\setlist[enumerate]{align=left, leftmargin=0pt, labelindent=15pt, labelwidth=0pt, itemindent=!}
\setlist[enumerate,2]{labelindent=30pt}


\begin{document}

Generally, it extends the idea of the derivative from realvalued functions of one real variable to functions on normed spaces.

The Fréchet derivative should be contrasted to the more general Gateaux derivative which is a generalization of the classical directional derivative.

\begin{enumerate}

  \item Generally, it extends the idea of the derivative from realvalued functions of one real variable to functions on normed spaces.

  \item The Fréchet derivative should be contrasted to the more general Gateaux derivative which is a generalization of the classical directional derivative.

The Fréchet derivative should be contrasted to the more general Gateaux derivative which is a generalization of the classical directional derivative.

\begin{enumerate}

  \item Generally, it extends the idea of the derivative from realvalued functions of one real variable to functions on normed spaces.

Generally, it extends the idea of the derivative from realvalued functions of one real variable to functions on normed spaces.
  
  \item The Fréchet derivative should be contrasted to the more general Gateaux derivative which is a generalization of the classical directional derivative.  

\end{enumerate}

\end{enumerate}

\end{document}