(LaTeX) Matching TeX magic comments should be case insensitive

Describe the issue

TeX magic comments are, in most editors, case insensitive, so both lines below are interpreted:

% !TeX program = lualatex
% !TEX encoding = UTF-8
%   ^ note e vs. E here

but the MAGIC_COMMENT rule only highlights the TeX (first) line:

https://github.com/highlightjs/highlight.js/blob/2dd87a6ef58c8c886dd209076aa6661ffae89577/src/languages/latex.js#L106-L111

Which language seems to have the issue?

latex

Are you using highlight or highlightAuto?

I don’t know? highlight I think because the language is specified explicitly.

Sample Code to Reproduce

% !TeX program = lualatex
% !TEX encoding = UTF-8
%   ^ note e vs. E here

Expected behavior

In the sample above, lines 1 and 2 should be highlighted as MAGIC_COMMENT, and line 3 should be a regular COMMENT:

[schtandard]

@PhelypeOleinik Thanks a lot for your research! I mostly agree with your conclusions, except for two minor points. I don’t feel strongly about either of them, though.

• I would omit the optional space after the !. I have never seen this and according to your list only LaTeX-Workshop supports it. I guess the idea is to allow %! TeX and I sympathise with your point about remembering where spaces are allowed, but this feels like too much of a niche case to me.
• I agree that case mixing like tEx is a bit absurd, but should we maybe allow tex and bib? This seems a reasonable spelling to me (for the editors that support them) and is also in line with the “just use lowercase” default many technical users may be used to.

About the ^: At least TeXStudio accepts magic comments anywhere in the document with no restriction of being the only thing on that line. (I didn’t test any other editors.) While I myself only ever use them on the first lines of a document (with no indentation), I wouldn’t make that a requirement for highlighting.

With all this my suggested regex would be % ?!(?:T[eE]X|tex|BIB|bib). Any comments? (No pun intended.)

[PhelypeOleinik]

* I would omit the optional space after the `!`. I have never seen this and according to your list only LaTeX-Workshop supports it. I guess the idea is to allow `%! TeX` and I sympathise with your point about remembering where spaces are allowed, but this feels like too much of a niche case to me.

Sounds reasonable. Given the plethora of different implementations, some level of restriction is good, so I’m fine with no space after !.

* I agree that case mixing like `tEx` is a bit absurd, but should we maybe allow `tex` and `bib`? This seems a reasonable spelling to me (for the editors that support them) and is also in line with the "just use lowercase" default many technical users may be used to.

Sounds good too.

With all this my suggested regex would be % ?!(?:T[eE]X|tex|BIB|bib). Any comments? (No pun intended.)

Go for it! (the regex, not the pun 😃