Extending Shortcode attributes

Question

I've searched many places and tried many ways for this but no success.

I have a shortcode in my WP Theme like;

[recent_posts layout="thumbnails-on-side" columns="4" number_posts="4" offset="" cat_slug="" exclude_cats="" thumbnail="yes" title="no" meta="no" excerpt="no" excerpt_length="35" strip_html="yes" animation_type="0" animation_direction="down" animation_speed="0.1" class="" id=""][/recent_posts]

(It is Avada theme's recent posts shortcode). In the core, this shortcode executes

WP_Query( $args )

function to get posts. But this shortcode cannot be used with Custom Post Types because coders didn't put 'post_type' attribute to shortcode $args (so because of default value is 'posts', shortcode only fetches standard posts).

As a result, i would like to extend/define new extended version of this shortcode for adding 'post_type' attribute as a variable (because i would like to use it for many custom post types). How can i do that? Thanks.

Answer 1

Without seeing your code it is difficult to give you an exact answer. There is the shortcode_atts_{$shortcode} filter that was introduced in Wordpress 3.6. All attributes is run through this filter. It has to be noted that the $shortcode parameter needs to be set in shortcode_atts. I haven't seen shortcodes yet that has this parameter set though.

Your problem here is actually bigger that just the attributes as you will need to add the attribute and the post_type parameter to your query arguments. If the author did not supply a custom filter for the query arguments, then you are at a dead end street.

IMO, you have two choices here

• Contact the theme author and ask him to at the relevant code to the shortcode in his next update. I don't think that he/she will have an issue as this adds value to the shortcode

• Create a child theme and copy the shortcode to the child theme. Modify the shortcode as needed, and remember to change the function name and shortcode name accordingly. This way you will have a shortcode that fits your needs

Answer 2

Here's just an addition to the answer by @PieterGoosen.

There are few methods how one could modify the post type of WP_Query, that's inside a shortcode. Let's assume it's [recent_posts].

Method A) If the shortcode uses the third parameter of the shortcode_atts() (as @PieterGoosen mentioned) for example wpse, then:

/**
 * Method A: Using the shortcode_atts_$shortcode filter + pre_get_posts action
 */

add_filter( 'shortcode_atts_wpse', function ( $out, $pairs, $atts )
{
    if( isset( $atts['post_type'] ) && $post_type = $atts['post_type'] )
    {
        add_action( 'pre_get_posts', function ( $q ) use ( $post_type )
        {
            static $activated = false;
            if( ! $activated )
            {
                $q->set( 'post_type', santize_key( $post_type ) );
                $activated = true;
            }
        }
    }       
    return $out;
} );

Here you can see my other answer on how to use this filter.

Method B) Else, we can re-register the shortcode with a new callback.

Change it from old_recent_posts to new_recent_posts:

/**
 * Method B: Re-register the shortcode
 */

add_action( 'after_setup_theme', function()
{
    if( function_exists( 'old_recent_posts' ) )
    {
        remove_shortcode( 'recent_posts', 'old_recent_posts' );
        add_shortcode(    'recent_posts', 'new_recent_posts' );
    }

} );

function new_recent_posts( $atts = [], $content = '' )
{
    if( isset( $atts['post_type'] ) && $post_type = $atts['post_type'] )
    {
        add_action( 'pre_get_posts', function ( $q ) use ( $post_type )
        {
            static $activated = false;
            if( ! $activated )
            {
                $q->set( 'post_type', santize_key( $post_type ) );
                $activated = true;
            }
        }
    }       
    return old_recent_posts( $atts = [], $content = '' );
}

Here you can see how @toscho replaces the shortcode callback, in the same question as my linked answer above.

Note that I didn't test this, but hopefully you can adjust this to your needs.