Out of stock display up-sells

add_action( 'woocommerce_single_product_summary', function() {

	// Out Of Stock
	global $product;
	if( $product && ! $product->is_in_stock() ) {

		// Get Upsells
		$upsells = $product->get_upsells();
		if( $upsells ) {

			// Yield To Parent Product IDs
			foreach( $upsells as &$product_id_loop ) {
				$product_loop = wc_get_product( $product_id_loop );
				if( ! $product_loop ) {
					continue;
				}
				if( $product_loop->is_type( 'variation' ) ) {
					$product_id_loop = $product_loop->get_parent_id();
				}
			}

			// Show Upsells Template
			echo '
				<p style="font-size: 21px;">
					Currently
					<strong>out of stock</strong> –
					Consider these alternatives:
				</p>
			';
			echo do_shortcode(
				sprintf(
					'[products limit="2" columns="2" ids="%s"]',
					implode( ',', $upsells )
				)
			);
			return;
		}
	}

} );