[wp-trac] Re: [WordPress Trac] #8553: preg_replace_callback in do_shortcode returns empty for large posts

[WordPress Trac]

#8553: preg_replace_callback in do_shortcode returns empty for large posts
---------------------------+------------------------------------------------
 Reporter:  AaronCampbell  |        Type:  defect (bug)
   Status:  new            |    Priority:  high        
Milestone:  2.9            |   Component:  Shortcodes  
  Version:                 |    Severity:  normal      
 Keywords:  needs-patch    |  
---------------------------+------------------------------------------------

Comment(by Denis-de-Bernardy):

 Adding a /x param to make things more readable... The current one is:

 {{{
 "/
 (.?)                # optionally catch an extra bracket used to escape
 shortcode
 \[($tagregexp)\b    # begin shortcode
   (.*?)             # optional attributes (non-greedy, stops on close
 bracket)
   (?:(\/))?         # optional slash to indicate a closing tag, not always
 set
   \]                # closing bracket
 (?:                 # optional content and closing shortcode
   (.+?)             # the content
   \[\/\2\]          # close shortcode with a back reference
 )?
 (.?)                # optionally catch an extra bracket used to escape
 shortcode
 /x"
 }}}

 you're suggesting:

 {{{
 "/
 (.?)                # optionally catch an extra bracket used to escape
 shortcode
 \[($tagregexp)\b    # begin shortcode
   ([^\]]*?)         # optional attributes (non-greedy), equivalent to
 using a dot
   (\/)?             # optional slash to indicate a closing tag, always set
   \]                # closing bracket
 (?:                 # optional content and closing shortcode
   (.+?)             # the content
   \[\/\2\]          # close shortcode with a back reference
 )?
 (.?)                # optionally catch an extra bracket used to escape
 shortcode
 /x"
 }}}

 the suggestion in #9264 is the following:

 {{{
 "/
 (.?)                # optionally catch an extra bracket used to escape
 shortcode
 \[($tagregexp)\b    # begin shortcode
   (.*?)             # optional attributes (non-greedy, stops on close
 bracket)
   (?:(\/))?         # optional slash to indicate a closing tag, not always
 set
   \]                # closing bracket
 (
   ?(4)              # stop if we already have 4 back references
                     # it would mean we've a slash bracket
   |                 # else
   (?:               # optional content and closing shortcode
     (.+?)           # the content
     \[\/\2\]        # close shortcode with a back reference
   )?
 )?
 (.?)                # optionally catch an extra bracket used to escape
 shortcode
 /x"
 }}}

 A few notes:

  - Using your patch would remove the possibility for the optimization in
 #9264 (since we'd always have.
  - Your attribute-related regex might be a bit more efficient from a
 performance standpoint.

 Personally, I was hoping that the optimization in the other ticket would
 allow you to do [foo/] in order to optimize your way through the mess.

 All of these patches, however, leave a few fundamental issues behind:

  1. Something like [foo[bar] get treated as a foo shortcode with [bar as
 an attribute

  2. We can get brackets in a shortcode's content, which can potentially
 lead to nested shortcodes:

 {{{
 [foo]bar[][/foo]
 [foo][bar/][/foo]
 }}}

  3. A non-closed shortcode can gobble up an entire document before the
 regex bails and decides that it has no closing shortcode:

 {{{
 [foo]
 long document that runs into the backtrack limit starts here
 }}}

 It's the two last points which I believe are troubling. I take it that
 some users actually want brackets in shortcodes, so fixing point 2
 probably isn't an option. Bailing after, say, 1000 characters after the
 start of the content might be a good bet.

 Would you mind attaching your post's source in a text file, exactly as it
 is in the WP editor, and specify the plugins you're using?

-- 
Ticket URL: <http://core.trac.wordpress.org/ticket/8553#comment:36>
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