Problems with highlight.js

Question

Stack Exchange switched their syntax highlighting parser to highlight.js (announcement). This is a clear downgrade for TeX (for now). However, highlight.js is said to be "actively developed" which makes me hopeful that this can be resolved in the medium term.

This question can be used to collect issues with the new syntax highlighting and track progress on solving them. Please

1. post one answer per issue with a code snipped showing the problem,
2. create an issue on highligh.js' Github page and
3. mark the problem as solved in the answer when it has been resolved.

---

_{While this is really, really annoying, I believe it could also be an opportunity. The source file for the highlight.js LaTeX highlighting looks rather rudimentary, so we might be able to "take over" and improve it to our liking, maybe even improving some aspects of the old highlighting. I will try to find some time to get to know their system and see if I can't do that myself. Who knows, maybe we can finally get the LaTeX3 highlighting (as a separate language) I have been dreaming of..}

Answer 1

There is (usually) no syntax highlighting inside braces

[fixed in highlight.js 10.3]

Sample:

\foo{\foo\bar \\\\\baz}

Github issue

Answer 2

Backslashes are not highlighted as part of the control sequence

[fixed in highlight.js 10.3]

Sample:

\foo\bar \\\\\baz

Github issue

Answer 3

@ ("at") isn't recognized as a valid character in a command name

[fixed in highlight.js 10.3]

Many hundreds (thousands?) of LaTeX2 commands employ the @ character in their names -- usually after one issues an explicit or implicit \makeatletter directive. Consider the following example (taken from an old answer of mine):

\makeatletter
\renewcommand\p@subsection{\thesection}
\renewcommand\p@subsubsection{\p@subsection\thesubsection}
\makeatother

If coloring of macro names is to be performed at all, it is crucial that the coloring scheme be informed that @ can be a valid character in command names.

Answer 4

Incorrect identification of scope of a macro definition

[fixed in highlight.js 10.3 (no such identification takes place)]

Consider the following example

\newcommand\sorted[1]{\directlua{sorted(\luastringN{#1})}}

Observe that the final three characters -- )}} -- aren't colored green even though they clearly belong to the scope of the argument of the \sorted macro.

The remedy would be not to look for the very first instance of } but for instance that matches the opening { character.

Answer 5

Very difficult to distinguish comments from ordinary text.

Consider

Hello World. % A comment.

The shade of gray that's used to highlight what's a comment is quite dark, making it anything but straightforward to identify comments visually. Please reinstate the old scheme, which used a much lighter shade of gray to denote comments.

Answer 6

LaTeX3-semantics for valid macro names aren't recognized.

[fixed in highlight.js 10.3]

With LaTeX3, the characters _ (underscore) and : (colon) may be (in fact, must be) used in various macro names. Take the following code snippet:

\seq_set_eq:NN \l__ralph_seq \l__alph_seq
\seq_set_eq:NN \l__rAlph_seq \l__Alph_seq
\seq_set_eq:NN \l__ralphAlph_seq \l__alphAlph_seq
\seq_set_eq:NN \l__rAlphalph_seq \l__Alphalph_seq
\seq_reverse:N \l__ralph_seq
\seq_reverse:N \l__rAlph_seq
\seq_reverse:N \l__ralphAlph_seq
\seq_reverse:N \l__rAlphalph_seq
\seq_set_eq:NN \l__custom_order_seq \l__Alphalph_seq

Because the new coloring scheme is evidently unaware of the uses of : and _ in command names, the scheme makes it very hard to figure out what's going on.

Answer 7

Incorrect display of array or tabular parameters when there is @{}

[fixed in highlight.js 10.3 (no such identification takes place)]

    \begin{array}{c@{}cc}
        a & b & c\\
        d & e & f
    \end{array}
    \begin{tabular}{c@{}cc}
        a & b & c\\
        d & e & f
    \end{tabular}

In the above examples {c@{} is green whereas cc} is black.