fix(python) identifiers starting with underscore not highlighted

[anlambert]

Hello and thanks for maintaining that great library.

I noticed a regression in highlightjs.js 11.0, Python identifiers starting with an underscore
character (__init__ for instance) are no longer highlighted (introduced in 952fa0a).

That PR fixes that issue and add new markup tests to cover it.

On a related note, Python 3.0 introduces additional characters from outside the ASCII range for identifiers. Adding support for those in highlight.js is out of that PR scope and does not seem easy to implement but I could try to have a look when I have some time.

[joshgoebel]

On a related note, Python 3.0 introduces additional characters from outside the ASCII range for identifiers.

If it's along the lines of #2756 then it's not a high priority and needs some considerable effort and further research.

[anlambert]

On a related note, Python 3.0 introduces additional characters from outside the ASCII range for identifiers.

If it's along the lines of #2756 then it's not a high priority and needs some considerable effort and further research.

That's what I thought too, ECMA 2018 could help here with its unicode category support in RegExp but it is only supported in recent browsers. So yes, this needs considerable effort and testing on the subject.

[joshgoebel]

only supported in recent browsers

We're mostly fine with supporting only more recent browsers. Safari is a hold out on look-behind regex, but we're mostly ES2015/2018 already otherwise in several ways...

unicode category support in RegExp

If you skim the other issue you'll see the issue is /u seemed significantly slower in testing - and for a feature that no one is asking for (you make only the second person to mention it) it doesn't seem worth any slow down, much less a significant one. So it's pretty much just on hold until someone who cares a lot pours some time into it.

[joshgoebel]

Please add changelog entry.

[anlambert]

Please add changelog entry.

Done. I also updated new markup test with the class starting with an underscore case.

[joshgoebel]

Thanks so much!