How to get all `supports` attributes by post type?

There exists the get_all_post_type_supports() to get the supported features for a given post type. It’s a wrapper for the _wp_post_type_features global variable:

/**
 * Get all the post type features
 *
 * @since 3.4.0
 *
 * @global array $_wp_post_type_features
 *
 * @param string $post_type The post type.
 * @return array Post type supports list.
 */
function get_all_post_type_supports( $post_type ) {
        global $_wp_post_type_features;

        if ( isset( $_wp_post_type_features[$post_type] ) )
                return $_wp_post_type_features[$post_type];

        return array();
}

Example:

Here’s an usage example from the wp shell for the 'post' post type:

wp> print_r( get_all_post_type_supports( 'post' ) );
Array
(
    How to get all `supports` attributes by post type? => 1
    [editor] => 1
     => 1
    [thumbnail] => 1
    [excerpt] => 1
    [trackbacks] => 1
    [custom-fields] => 1
    [comments] => 1
    [revisions] => 1
    [post-formats] => 1
)

Another useful wrapper is get_post_types_by_support().