Time to finally allow negative lookbehind?

[joshgoebel]

I just checked and the latest versions of Safari (that now support negative lookbehind) [16.4, 16.5, etc] go all the way back to Big Sur, supporting:

• Big Sur (November 12, 2020)
• Montery (October 25, 2021)
• Ventura (October 24, 2022)
• Sonoma (September 26, 2023)

Big Sur support extends all the way back to Mac's from 2013. I have some sympathy for those who hold off a while on OS releases, but little for those who would avoid installing the newest version of Safari (since often there are security fixes, etc)... so I think if we allow support for negative lookbehind we'd only be dropping support for Mac's 10+ years old or those refusing to upgrade their Safari - in which case I'd suggest they use another browser instead, such as Chrome.

So I say it's time to allow look-behind...

Thoughts, @allejo ?

[allejo]

As long as the introduction of negative lookbehinds in grammars is introduced in 12.0 and not in our 11.x series, you have my support 👍

Solely on principle for semantic versioning, I'd be hesitant to introduce a breaking change in browser support in a minor release

[kuenzign]

I have quite a few personal lexers that really require the use of lookbehinds as my current workarounds do not work for all cases. Is there a timeline on when lookbehinds will be allowed?

[joshgoebel]

Well if they are truly personal, just use them... it's only the core library that we aren't allowing them in v11 because of semantic versioning. I haven't had much time lately to do a major release but it's a long weekend so I'll take a look at where we stand with v12...

@allejo The old website handled us being able to publish two major versions at once - and it just did the right thing (pay attention to the new one)... does the new website share this characteristic - what if say we pushed a few 12.0.0-beta or alpha relases? (the old website would also ignore alpha/betas, etc)

[kuenzign]

Ah it looks like all I needed to do was change the ecmaVersion to 2018 in the config to allow it to work. Thanks!

[joshgoebel]

Closing as the decision has been made, this will be allowed when v12 ships.