WordPress Plugin: Limit the display of attachments (in the admin screens) to the ones uploaded by the current user

attachment_role_limit.php

<?php
/**
 * Plugin Name: Attachment Role limit
 * Plugin URI:  https://gist.github.com/franz-josef-kaiser/0688bfb7fda30e815ef8
 * Description: Limit the display of attachments (in the admin screens) to the ones uploaded by the current user.
 * Version:     2015.02.24
 * Author:      Franz Josef Kaiser <wecodemore@gmail.com>
 * Author URI:  http://unserkaiser.com
 * License:     MIT
 * License URI: https://tldrlegal.com/license/mit-license
 */

class AttachmentRoleLimitService
{
	/**
	 * @param \WP_Query $query
	 */
	public function setup( \WP_Query $query = null )
	{
		if ( ! is_admin() )
			return;

		if (
			current_user_can( 'manage_options' )
			// @TODO Add additional capability checks for not-affected roles here
			// or current_user_can( 'another_capability' )
			or 'attachment' !== $query->get( 'post_type' )
		)
			return;

		$query->set( 'author', get_current_user_id() );
	}
}

add_filter( 'pre_get_posts', array( new AttachmentRoleLimitService, 'setup' ) );