Preventing line break at the start of a long name in `\lstinline`

Question

This question has developed from How to deal with very long lstinline-phrases like long class names?.

That question is about line breaking inside a \lstinline phrase. I have provided an answer which automatically hyphenates on capital letters, and then, in a comment, I realized it could sometimes be useful to have automatic hyphenation on underscores _ as well.

I managed to implement this, but one glitch remains: I would like to prevent automatic _-hyphenation at the start of the name (in Python, for example, this is common situation, as by convention, internal names start with an underscore (or two)).

\documentclass{article}
\usepackage[paperwidth=10cm,paperheight=5cm]{geometry}
\pagestyle{empty}
\usepackage{lstdoc}
\lstMakeShortInline[literate={\_}{\_}{1\discretionary{\_}{}{}}]|

\begin{document}
\textbf{Good line break:} in this paragraph the line break in the
python's variable |a_python_style_name| is good!

\textbf{Bad line break:} the internal variable |_internal_python_name|
is not hyphenated very nicely in this paragraph.
\end{document}

Answer 1

Circumvent the \discretionary insertion by inserting something else just for the start. Here are some options:

\documentclass{article}
\usepackage[paperwidth=10cm,paperheight=8cm]{geometry}
\pagestyle{empty}
\usepackage{lstdoc}
\lstset{mathescape=true}
\lstMakeShortInline[literate={\_}{\_}{1\discretionary{\_}{}{}} {~}{\_}{1}]|
\newcommand{\preunderscore}{\_}

\begin{document}
\textbf{Good line break:} in this paragraph the line break in the
python's variable |a_python_style_name| is good!

\textbf{Bad line break:} the internal variable |_internal_python_name|\par
|_internal_python_name|

\textbf{Bad line break:} the internal variable |~internal_python_name|\par
|~internal_python_name|

\textbf{Bad line break:} the internal variable |$\preunderscore$internal_python_name|\par
|$\preunderscore$internal_python_name|
\end{document}

With mathescape you can insert a macro instead of a literate replacement for _. Alternatively, use a different literate character for the start. There are differences in spacing.