Improve get_shortcode_regex performance

[Antek88]

Hi,

It's my first PR to WordPress, I hope it goes well :).

I ran Blackfire on my homepage (eCommerce shop with Woocommerce plugin). After analyzing it, I see that many shortcodes are parsing, but I don't use it directly. After some investigation, I see that in
get_shortcode_regex is many unnecessary call implode/array_map function for empty $tagsname argument.
After this patch, page response time is reduced by almost ~200ms.
Blackfire profile screen:

Trac ticket: https://core.trac.wordpress.org/ticket/54289#ticket

[flixos90]

Thank you for the report @Antek88, and welcome to Trac.

While this may be a valid ticket, I think at this point short codes aren't recommended anymore, so I'd consider this low severity. That said, since you have already opened a pull request, it might be straightforward enough to address. Let me take a look.

[oglekler]

Patch needs refresh and it also needs instruction how to test it.

[wildworks]

This ticket was featured on today's 6.9 Bug Scrub.

Patch needs refresh and it also needs instruction how to test it.

As with the previous comment, I think this is necessary to move this ticket forward.

@piotrantosik hi, thanks for the PR. Could you provide more info and testing instructions in the Trac ticket?

[Antek88]

Sorry, it's 4 years 4-year-old PR, I'm not working with WordPress anymore and don't remember :)

[westonruter]

Punting since we're close to 6.9-beta1. Clearing out owner since no one is actively working on this right now.