Allow symlinked plugins to function with WooCommerce plugin_url() call: issue #2859: https://github.com/woothemes/woocommerce/issues/2859

wc-all-symlink-plugins-url.php

<?php

add_filter( 'plugins_url', 'allow_symlink_plugins_url', 10, 3 );

/**
 * Allow symlinked plugins to function.  This was made necessary by a change in
 * the standard WooCommerce plugin_url() method from:
 *
 * plugins_url( basename( plugin_dir_path( __FILE__ ) ), basename( __FILE__ ) );
 *
 * which worked with symlinks, to:
 *
 * untrailingslashit( plugins_url( '/', __FILE__ ) )
 *
 * which does not.
 *
 * Note: we use '/' as the path to detect when to "fix" the url because that
 * seems to be the new convention.  There is some possibility of this breaking
 * a 3rd party plugin that does not follow the same convention.  We'll just have
 * to try and do our best to remember this function exists
 *
 * @param string $url the url generated by plugins_url()
 * @param string $path the path passed to plugins_url()
 * @param string $plugin the plugin passed to plugins_url()
 */
function allow_symlink_plugins_url( $url, $path, $plugin ) {

  if ( '/' === $path && $plugin ) {

		remove_filter( 'plugins_url', 'allow_symlink_plugins_url', 10, 3 );

		$url = plugins_url( basename( plugin_dir_path( $plugin ) ), basename( $plugin ) );

		add_filter( 'plugins_url', 'allow_symlink_plugins_url', 10, 3 );
	}

	return $url;
}