Change Stock By Product Tag

Hi Julian,

Thanks for reaching out.

At this moment, it is not possible to update stock only for products with a specific tag only. But I have passed your request to our development team. They will get back to you as soon as possible.

Kind regards,
Moshtafizur

Hi, Julian,

Haven’t we solved it with you with this snippet?

/**
 * alg_wc_stock_triggers_function_increase.
 */
add_filter( 'alg_wc_stock_triggers_function_increase', function () {
    return 'my_wc_maybe_increase_stock_levels';
} );

/**
 * my_wc_maybe_increase_stock_levels.
 *
 * @see https://github.com/woocommerce/woocommerce/blob/7.7.0/plugins/woocommerce/includes/wc-stock-functions.php#L123
 */
if ( ! function_exists( 'my_wc_maybe_increase_stock_levels' ) ) {
    function my_wc_maybe_increase_stock_levels( $order_id ) {
        $order = wc_get_order( $order_id );

        if ( ! $order ) {
            return;
        }

        $stock_reduced    = $order->get_data_store()->get_stock_reduced( $order_id );
        $trigger_increase = (bool) $stock_reduced;

        // Only continue if we're increasing stock.
        if ( ! $trigger_increase ) {
            return;
        }

        my_wc_increase_stock_levels( $order );

        // Ensure stock is not marked as "reduced" anymore.
        $order->get_data_store()->set_stock_reduced( $order_id, false );
    }
}

/**
 * my_wc_increase_stock_levels.
 *
 * @see https://github.com/woocommerce/woocommerce/blob/7.7.0/plugins/woocommerce/includes/wc-stock-functions.php#L268
 */
if ( ! function_exists( 'my_wc_increase_stock_levels' ) ) {
    function my_wc_increase_stock_levels( $order_id ) {
        if ( is_a( $order_id, 'WC_Order' ) ) {
            $order    = $order_id;
            $order_id = $order->get_id();
        } else {
            $order = wc_get_order( $order_id );
        }

        // We need an order, and a store with stock management to continue.
        if ( ! $order || 'yes' !== get_option( 'woocommerce_manage_stock' ) || ! apply_filters( 'woocommerce_can_restore_order_stock', true, $order ) ) {
            return;
        }

        $changes = array();

        // Loop over all items.
        foreach ( $order->get_items() as $item ) {
            if ( ! $item->is_type( 'line_item' ) ) {
                continue;
            }

            // Only increase stock once for each item.
            $product            = $item->get_product();
            $item_stock_reduced = $item->get_meta( '_reduced_stock', true );

            if ( ! $item_stock_reduced || ! $product || ! $product->managing_stock() ) {
                continue;
            }

            // Check order status and product tag
            $check_order_status     = array( 'your-order-status' );
            $check_product_tag_slug = 'your-product-tag';
            if ( $order->has_status( $check_order_status ) ) {
                $tags = wc_get_product_terms( ( $product->get_parent_id() ? $product->get_parent_id() : $product->get_id() ), 'product_tag' );
                $tags = wp_list_pluck( $tags, 'slug' );
                if ( in_array( $check_product_tag_slug, $tags ) ) {
                    continue;
                }
            }

            $item_name = $product->get_formatted_name();
            $new_stock = wc_update_product_stock( $product, $item_stock_reduced, 'increase' );

            if ( is_wp_error( $new_stock ) ) {
                /* translators: %s item name. */
                $order->add_order_note( sprintf( __( 'Unable to restore stock for item %s.', 'woocommerce' ), $item_name ) );
                continue;
            }

            $item->delete_meta_data( '_reduced_stock' );
            $item->save();

            $changes[] = $item_name . ' ' . ( $new_stock - $item_stock_reduced ) . '→' . $new_stock;
        }

        if ( $changes ) {
            $order->add_order_note( __( 'Stock levels increased:', 'woocommerce' ) . ' ' . implode( ', ', $changes ) );
        }

        do_action( 'woocommerce_restore_order_stock', $order );
    }
}

The code is not very small, but 99% of it is a copy of these two standard WooCommerce functions:
https://github.com/woocommerce/woocommerce/blob/7.7.0/plugins/woocommerce/includes/wc-stock-functions.php#L123
https://github.com/woocommerce/woocommerce/blob/7.7.0/plugins/woocommerce/includes/wc-stock-functions.php#L268

You need to modify only these two lines in the snippet:

$check_order_status     = array( 'your-order-status' );
$check_product_tag_slug = 'your-product-tag';

That is, now the snippet will not increase stock on order status change to your-order-status for the products with the your-product-tag tag – you need to set your order status and product tag here.