Cfrgtkky

Given the following minimal example

documentclass[parskip=full]{scrreprt}

usepackage[onehalfspacing]{setspace}

usepackage{enumitem}

usepackage{lipsum}



setlist{

parsep=parsep,

itemsep=-.5parsep,

topsep=-.5parsep,

partopsep=.5parsep

}



begin{document}

lipsum[1]

begin{itemize}

item list

item between

item paragraphs

end{itemize}

lipsum[2]



begin{itemize}

item list

item in

item own

item paragraph

end{itemize}



lipsum[3]

begin{itemize}

item list

item above

item paragraph

end{itemize}



lipsum[4-5]

end{document}

The first and second lists are spaced as expected, with the second list spaced as an individual paragraph (compare with last two paragraphs).
However, the third list is spaced in the same way as the first one, even though it is followed by an unrelated paragraph.

This answer states that partopsep is added above and below a list environment if it begins a new paragraph.
Is there a (reasonably simple) way to get a partopsep added only to the bottom if a list environment is followed by a new paragraph?

Interesting question. Here's my attempt at a solution. You have to enable it for a particular list by adding first={useparbotsep}. It modifies one macro from latex.ltx (@doendpe), but hopefully in a way that only makes a difference when useparbotsep is called.

documentclass[parskip=full]{scrreprt}

usepackage[onehalfspacing]{setspace}

usepackage{enumitem}



makeatletter

newskipbottomsepadd

newififparbotsep

defuseparbotsep{%

  globalbottomsepaddpartopsep

  global@topsepaddtopsep

  globalparbotseptrue}

def@doendpe{% <- modified from latex.ltx (hopefully with no side effects)

  @endpetrue

  defpar{@restorepar

    clubpenalty@clubpenalty

    everypar{}%

    ifparbotsep

      if@endpevskipbottomsepaddfi

      globalparbotsepfalse

    fi

    par@endpefalse}

    everypar{{setboxz@lastbox}%

      everypar{}@endpefalse}}

makeatother



setlist{

  parsep=parsep,

  itemsep=-.5parsep,

  topsep=-.5parsep,

  partopsep=.5parsep,

  first={useparbotsep}

}



begin{document}



vskip 5pthrulevskip 5pt





List within paragraph:

begin{itemize}

  item List item.

  item List item.

  item List item.

end{itemize}

End of List within paragraph.



vskip 5pthrulevskip 5pt





List as its on paragraph:



begin{itemize}

  item List item.

  item List item.

  item List item.

end{itemize}



Paragraph following list as its own paragraph.



vskip 5pthrulevskip 5pt





List above paragraph:



begin{itemize}

  item List item.

  item List item.

  item List item.

end{itemize}

Text following list.



vskip 5pthrulevskip 5pt





List below paragraph:

begin{itemize}

  item List item.

  item List item.

  item List item.

end{itemize}



Paragraph following list.



vskip 5pthrulevskip 5pt

end{document}