Content may be removed on front-end during group inner container restoration on some PHP versions

[jeremyfelt]

Description

The regex used in gutenberg_restore_group_inner_container() does not appear to work as intended on all PHP versions for some content. This can lead to content being removed from the front-end when Gutenberg 10.3.0 is activated.

An initial example of content that breaks with the regexes in that function: https://3v4l.org/Q9mVk

• PHP 5.6, 7.3, 7.4, and 8 return 1 for the initial preg_match() and will then not process the content with the second regex.
• PHP 7.0, 7.1, and 7.2 return false for the initial preg_match() and then assign NULL to $updated_content in the second regex.

The sample content is structured as:

• Group
  • Group
    • Heading
    • Columns
      • Column
      • Column
  • Heading
  • Columns
    • Column
    • Column

I'm not confident if this is due to a group wrapping a group, or what, but it is content that was working on my home page with Gutenberg 10.2.0 and then stopped working on upgrade to 10.3.0. Deactivating the plugin brings the content immediately back. The content always appears fine in the editor.

Related #30443, #30453

Code snippet (optional)

Markup and regex example from gutenberg_restore_group_inner_container(): https://3v4l.org/Q9mVk

WordPress information

• WordPress version: 5.7.0
• Gutenberg version: 10.3.0
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? Yes

[youknowriad]

Thanks for writing this issue. I'm trying to improve the regex here #30460 but still noticing some content loss with the example content provided in #30443

Feel free to chime-in and improve the regex. I'm no expert there.

[youknowriad]

So for me the regex in #30460 seems correct but there might be a memory problem for long posts like this one https://3v4l.org/gUpmT

[ockham]

Trying to swap the m modifier for an s, and replacing the obscure (\s|\S|.)* by just .*: https://3v4l.org/H20C4

[ockham]

ms (both modifiers together) also works, as long as we replace (\s|\S|.)* by .* (which the s modifier allows us to do).

Edit: Test: https://3v4l.org/bVPFM

[nbatteur]

HI, as requested here is my configuration:

Server architecture	Linux 3.10.0-693.11.6.el7.x86_64 x86_64
Web server	Apache
PHP version	7.3.27 (Supports 64bit values)
PHP SAPI	fpm-fcgi
PHP max input variables	2000
PHP time limit	300
PHP memory limit	2048M
Max input time	6000
Upload max filesize	64M
PHP post max size	64M
cURL version	7.29.0 NSS/3.53.1
Is SUHOSIN installed?	No
Is the Imagick library available?	Yes
Are pretty permalinks supported?	Yes
.htaccess rules	Custom rules have been added to your .htaccess file.

[ockham]

@nbatteur Thanks for sharing your config. We believed we've fixed the issue you were experiencing, and we released Gutenberg v10.3.1 to include the relevant fixes. Can you try if that version fixes the issue for you?

[nbatteur]

Its good ! I just tested on our test machine and everything works again with this new version. Thank you very much for the work done!
And on prod server too.