Question

This is the regular expression used for “shortcodes” in WordPress (one for the whole tag, other for the attributes).

return '(.?)\[('.$tagregexp.')\b(.*?)(?:(\/))?\](?:(.+?)\[\/\2\])?(.?)';
$pattern = '/(\w+)\s*=\s*"([^"]*)"(?:\s|$)|(\w+)\s*=\s*\'([^\']*)\'(?:\s|$)|(\w+)\s*=\s*([^\s\'"]+)(?:\s|$)|"([^"]*)"(?:\s|$)|(\S+)(?:\s|$)/';

It parses stuff like

[foo bar="baz"]content[/foo]

or

[foo /]

In the WordPress trac they say it’s a bit flawed, but my main problem is that it don’t support shortcodes inside the attributes, like in

[foo bar="[baz /]"]content[/foo]

because the regex stops the main shortcode at the first appearance of a closing bracket, so in the example it renders

[foo bar="[baz /]

and

"]content[/foo]

shows as it is.

Is there any way to change the regex so it bypass any occurrence of [ with ] and its content when occurs between the opening tag or self-closing tag?

Answer 1

I found a way to fix it:
First, change the shortcode regex from:

(.?)\[('.$tagregexp.')\b(.*?)(?:(\/))?\](?:(.+?)\[\/\2\])?(.?)

To:

(.?)\[('.$tagregexp.')\b((?:[^\[\]]|(?R)|.)*?)(?:(\/))?\](?:(.+?)\[\/\2\])?(.?)

And then change the priority of the do_shortcode function to avoid conflict with wptexturize, the function that stylize the quotes and mess up this fix. It don’t have problems with wpautop because that’s somewhat fixed with another recent function I think.

Before:

add_filter('the_content', 'do_shortcode', 11); // AFTER wpautop() 

After:

add_filter('the_content', 'do_shortcode', 9);  

I submitted this to the trac and is on some kind of permanent hiatus. In the meanwhile I figure if I can make a plugin to apply my fix without changing the core files. Override the filter priority is easy, but I have no idea of how to override the regex.