Problem with custom Latex environment inside of custom list environment items

[abenthy]

Hello, I'm trying to read a Latex document in Pandoc with the following structure:

\documentclass{article}

\newenvironment{myenumerate}{\begin{enumerate}}{\end{enumerate}}
\newenvironment{myenvironment}{}{}

\begin{document}

\begin{myenumerate}
\item{foo\begin{myenvironment}bar\end{myenvironment}}
\end{myenumerate}

\end{document}

Pandoc v. 2.17.1.1 (pandoc -t json example.tex) gives me the following error

Error at "example.tex" (line 13, column 2):
unexpected end of input
expecting \end{enumerate}

 ^

The document compiles without errors with pdflatex.

What I have tried / observed:

• The problem seems to be somehow related to the curly brackets after \item. If I replace \item{...} by \item... it works (I don't know why).
• If I remove the text foo, it works (again, I don't know why).
• Replacing myenumerate by a list defined with \newlist from the enumitem package doesn't fix the error.
• If I replace the usage of myenumerate with the standard enumerate environment, it works.
• If I replace \begin{myenvironment}bar\end{myenvironment} with \begin{center}bar\end{center}, it works.

Does someone know what cause the problem here? I have a document that uses custom lists like above that I would like to convert with Pandoc, if possible without changes to the document. However, changes to the macro definitions would be no problem as a fix for me.

Thanks for your fantastic work on parsing Latex by the way, most of my documents work great!

[jgm]

Here's what I note:

1. If you comment out the definition of newenvironment, then pandoc succeeds, but puts the content of newenvironment in a special div block.
2. As you note, if you remove the {..} around the list item, pandoc succeeds and you get a list item foobar (which I think is what you want)
3. As you note, removing foo also works.

I'll have to dig into the code to figure this one out.

[jgm]

More experiments:

% pandoc -f latex -t native
\newenvironment{x}{}{}
{foo\begin{x}bar\end{x}}
^D
Error at (line 2, column 24):
unexpected Tok (line 2, column 24) Symbol "}"
expecting end of input
{foo\begin{x}bar\end{x}}
                       ^

% pandoc -f latex -t native
{foo\begin{x}bar\end{x}}
^D
[ Para [ Str "foo" ]
, Div ( "" , [ "x" ] , [] ) [ Para [ Str "bar" ] ]
]

% pandoc -f latex -t native
\newenvironment{x}{}{}
^D
foo\begin{x}bar\end{x}
[ Para [ Str "foobar" ] ]

 % pandoc -f latex -t native
\newenvironment{x}{}{}
{\begin{x}bar\end{x}}
^D
[ Para [ Span ( "" , [] , [] ) [ Str "bar" ] ] ]

[jgm]

Even smaller:

{foo\bgroup bar\egroup }

which is how pandoc expands the environment
yields

Error at (line 1, column 24):
unexpected Tok (line 1, column 24) Symbol "}"
expecting end of input
{foo\bgroup bar\egroup }

This is the root issue, I think.

[jgm]

However this is fine!

\bgroup foo\bgroup bar \egroup\egroup