Red box drawn around question-mark operator in minted Erlang code

Question

I'm trying to include some Erlang code samples in a document using the minted package which include the ? operator to denote a message being received from a process. The code

\documentclass{minimal}
\usepackage{minted}
\begin{document}
\begin{minted}{erlang}
A ! Msg1,
receive
    A ? Msg2 ->
        ok
\end{minted}
\end{document}

produces the following output:

with the ? operator being treated differently to the ! operator, and having a red box drawn around it. How can I remove this box and have it treated in the same way as the ! operator? I presumed pygmentize would treat them similarly in this context. Is there any way I can check that this assertion is true, and if it's not, modify how pygmentize treats it accordingly?

Answer 1

Normally the red box indicates syntax errors in your source code (here Erlang). However, the language specific parsers used by Pygments (which in turn is used by minted) are incomplete. Apparently the Erlang parser cannot cope with the question mark as an identifier.

The best course of action is to file a bug with the maintainer of the Erlang lexer, Jeremy Thurgood or the Pocoo team who maintain Pygments.

Or you can fix the error yourself in your local Pygments installation by modifying pygments/lexers/functional.py – the error is probably just a missing question mark on line 659.

Answer 2

You may also override the pygments error command like this:

\expandafter\def\csname PY@tok@err\endcsname{}

That's not exactly the better solution, because it will hide all syntax errors of your code, but works perfectly for me. I still don't know what that line above means exactly, it just works.

I discover that by running pygments on command line and reading the output generated, like this (in my case I was working with html instead of Erlang):

pygmentize -f latex -O full -l html test.html