sale_products shortcode question

Having a crack at creating a custom shortcode but am getting a fatal error:

add_shortcode( 'cbs_sale_products', 'cbs_sale_products_function' );

public function cbs_sale_products( $atts ){
	    global $woocommerce_loop, $woocommerce;

	    extract( shortcode_atts( array(
			'category'      => '',
	        'per_page'      => '12',
	        'columns'       => '4',
	        'orderby'       => 'title',
	        'order'         => 'asc'
	        ), $atts ) );

		// Get products on sale
		$product_ids_on_sale = woocommerce_get_product_ids_on_sale();

		$meta_query = array();
		$meta_query[] = $woocommerce->query->visibility_meta_query();
	    $meta_query[] = $woocommerce->query->stock_status_meta_query();

		$args = array(
			'posts_per_page'=> $per_page,
			'orderby' 		=> $orderby,
	        'order' 		=> $order,
			'no_found_rows' => 1,
			'post_status' 	=> 'publish',
			'post_type' 	=> 'product',
			'orderby' 		=> 'date',
			'order' 		=> 'ASC',
			'meta_query' 	=> $meta_query,
			'post__in'		=> $product_ids_on_sale,
			'terms' 		=> $category
		);

	  	ob_start();
		$products = new WP_Query( $args );
		$woocommerce_loop['columns'] = $columns;
		if ( $products->have_posts() ) : ?>

			<?php woocommerce_product_loop_start(); ?>

				<?php while ( $products->have_posts() ) : $products->the_post(); ?>

					<?php woocommerce_get_template_part( 'content', 'product' ); ?>

				<?php endwhile; // end of the loop. ?>

			<?php woocommerce_product_loop_end(); ?>

		<?php endif;
		wp_reset_postdata();
		return '<div class="woocommerce">' . ob_get_clean() . '</div>';
	}

Any help would be very welcome ??

Kind regards,
JP

This is coming in WooCommerce 2.6 in a few weeks!

Perfect! Thank you Mike ??