id,summary,reporter,owner,description,type,status,priority,milestone,component,version,severity,resolution,keywords,cc
15155,Allow filtering of shortcode attributes,coffee2code,nacin,"It would be handy to have the ability to filter the array returned from `shortcode_atts()`.  This would allow plugins to take the default shortcode attributes, the user supplied attributes, and the merged array of those two into account prior to `shortcode_atts()` returning.  

Potential uses:
 * Override the default shortcode attributes (in a fashion)
 * Ignore certain attribute values from the user and instead use the defaults
 * Dynamically generate shortcode attribute values
 * Modifying the behavior of a shortcode handler via attributes without redefining and rewriting the handler, particularly if the shortcode handler doesn't present filters of its own

This would be particularly useful to modify the behavior of core-supplied shortcodes.  For instance, #14390 requests a way of omitting post thumbnails from the gallery shortcode.  Using this patch, this could easily be done via hooks in a number of ways (i.e. omit post thumbnails if the 'exclude' attribute isn't supplied, or always ignore post thumbnails, etc).  In fact, these hooks allow for custom exclusion of any number of images for any number of custom reasons.

The patch introduces two filters, ""shortcode_atts_$shortcode"" and ""shortcode_atts"".  The former allows hooking only the shortcode_atts for a specified shortcode, whereas the latter is a more generic hook.

`shortcode_atts()` really has no context, so I introduced an optional argument, `$shortcode`.  If supplied, the new hooks are fired.  I opted not to fire them if no `$shortcode` was supplied since the lack of context (namely, the name of the shortcode whose attributes are being processed) makes the use of the hooks a questionable proposition.  The patch amends all existing `shortcode_atts()` calls to include the new argument.  We'd want to promote use of the argument going forward, which is why I (perhaps overzealously) made use of  `_deprecated_argument()` to alert developers not to a deprecated argument, but to an added argument (is there a better way? making the argument required would of course break a lot plugins).

By way of example, here's a patch for #14390 making use of this patch to omit the post thumbnail from the gallery shortcode:

{{{
add_filter( 'shortcode_atts_gallery', 'gallery_shortcode_exclude_thumbnail', 10, 3 );

/**
 * Exclude post thumbnail image from gallery if user doesn't explicitly exclude any images
 *
 * @since 3.1
 * @param array $result The shortcode_atts() merging of $defaults and $atts
 * @param array $defaults The default attributes defined for the shortcode
 * @param array $atts The attributes supplied by the user within the shortcode
 * @return array The potentially modified $result array
 *
 */
function gallery_shortcode_exclude_thumbnail( $result, $defaults, $atts ) {
	if ( empty( $atts['exclude'] ) )
		$result['exclude'] = get_post_thumbnail_id();
	return $result;
}
}}}

Another example would be modifying the `[caption]` shortcode to prepend or append text to whatever caption the user provided.

{{{
function append_copyright_to_caption( $result, $defaults, $atts ) {
	$copyright = '© 2010 Example, Inc.';
	if ( isset( $result['caption'] )  && ! empty( $result['caption'] ) )
		$result['caption'] .= ""<br />$copyright"";
	else
		$result['caption'] =  $copyright;
	return $result;
}
add_filter( 'shortcode_atts_caption', 'append_copyright_to_caption', 10, 3);
}}}",enhancement,closed,normal,3.6,Shortcodes,2.5,normal,fixed,has-patch 3.5-early commit needs-codex,Denis-de-Bernardy wp@… Ken@… lancewillett 24-7@… chip@… kovshenin@… adambackstrom carstenbach dougal@… navjotjsingh@… xoodrew@… j@… dromsey@…