Changes to User-Specific-Content WP plugin to remove unauthorised posts from The Loop

main_plugin_fields.php

/*
These changes are for the plugin User-Specific-Content by Bainternet: https://wordpress.org/support/plugin/user-specific-content
The below adds the new filter to settings 
*/

$p->add_field(array(
    'label'   => __('Filter posts from The Loop?','bauspc'),
    'std'     => false,
    'id'      => 'run_on_the_loop',
    'type'    => 'checkbox',
    'section' => $setting,
    'desc'    => __('(check to stop posts appearing on archive / tags / category pages default unchecked)','bauspc')
    )
);

User-Specific-Content.php

<?php
/*
These changes are for the plugin User-Specific-Content by Bainternet: https://wordpress.org/support/plugin/user-specific-content
Add the below funciton inside the class bainternet_U_S_C
*/

/* Change Init */
public function U_S_C_init(){
	$options = $this->U_S_C_get_option();
	if ($options['run_on_the_content']){
		/* hook the_content to filter users */
		add_filter('the_content',array($this,'User_specific_content_filter'),20);
	}
	if ($options['run_on_the_excerpt']){
		/* hook the_excerpt to filter users */
		add_filter('the_excerpt',array($this,'User_specific_content_filter'),20);
	}
	// Here's the new stuff
	if ($options['run_on_the_loop']){
		/* hook pre_get_posts to filter posts by restrictions */
		add_action('pre_get_posts', array($this, 'User_specific_loop_filter'));
	}
	//allow other filters
	do_action('User_specific_content_filter_add',$this);
}

/**
 * Remove posts from The Loop where user does not have required access
 * Author: Fred Stark
 * Author URI: https://github.com/coagmano
 */
public function User_specific_loop_filter($query){

	if ( is_main_query() && !is_admin() && !is_singular() ) {
		global $current_user;
		get_currentuserinfo();

		$args = array(
			'relation' => 'OR',
			array(
				'key' => 'U_S_C_roles',
				'compare' => 'NOT EXISTS'
			)
		);

		if ( !empty( $current_user ) ) {
			$roles = $current_user->roles;

			foreach ($roles as $r) {
				$args[] = array(
					'key' => 'U_S_C_roles',
					'value' => $r,
					'compare' => 'LIKE'
				);
			}

		}

		$query->set('meta_query', $args);

		return $query;
	}
}