Dahu Weight Shipping

A weight-based WooCommerce shipping method, configurable per zone, with per-class rules and one-click shipping lines on manually created orders.

MIT licensed. Requires WordPress 6.0, PHP 7.4 and WooCommerce 7.0.

What it is for

A carrier contract is usually a table: up to two kilos, this much; up to five, that much. This plugin lets you paste that table into a field and prices every cart from it. The table belongs to the shipping zone, so a second country with a second contract is a second instance with its own table rather than a conditional rule.

The grid

One bracket per line, min-max:price, weights in the shop's own unit and prices excluding tax:

0-2:10
2-5:15
5-10:20
10-30:35

The minimum is excluded and the maximum included: 0-2:10 covers anything above 0 and up to 2. Past the last bracket, the last bracket's price applies.

Malformed lines are reported on screen rather than skipped silently, and a grid where no line is valid is not saved — the previous one is kept, because an empty grid prices every weight at zero and reads as free shipping.

Rules, as settings rather than as code

Per zone instance:

Manual orders

An Add shipping button on the order screen lists the methods available for that order's destination, names the zone they came from, and marks which ones this plugin can price. Choosing one creates the line, attaches it to that exact zone instance and prices it, in a single request.

The price comes from the same calculate_shipping() the checkout calls, on the same instance — not from a second copy of the pricing rules. A correction made by hand switches automatic pricing off for that line for good.

A side panel shows the weight that enters the grid, from the same code, so the figure shown and the figure billed cannot disagree.

Kits and bundles

A kit sold as one product is one parcel. Components are folded back into their kit on both sides — cart and order — so the kit is weighed and billed once. Recognised through the meta each plugin publishes: Dahu Composite (dahu_kit_parent), WooCommerce Composite Products (composite_parent, _composite_*) and WooCommerce Product Bundles (through its own get_product_from_item filter).

Extending

Pricing another carrier on manual orders

add_filter( 'dahu_weight_shipping_calculators', function ( $calculators ) {
    $calculators['my_carrier'] = function ( $order, $instance_id, $items_with_qty ) {
        // Return the cost excluding tax, plus any lines explaining it,
        // or a WP_Error with code 'manual' or 'no_rate'.
        return array(
            'cost'    => 12.5,
            'details' => array( 'flat rate from my carrier' ),
        );
    };
    return $calculators;
} );

Free shipping by coupon is applied to every calculator's result, in one place, so one order cannot come out free on one method and charged on another.

Other hooks

Deliberate limits

• No dimensions, volumetric weight or parcel count.
• No carrier API, labels or tracking.
• No splitting a cart into several parcels.
• A cart left with no shipping method is recorded, never papered over with an invented price.

Data

Nothing site-wide. Every setting belongs to a WooCommerce zone instance, which WooCommerce deletes with its zone. The only thing written elsewhere is a flag on a shipping line whose cost was edited by hand, and uninstalling keeps it — deleting it would quietly undo that decision, and the next recalculation would overwrite a price somebody corrected on purpose. Set the dahu_weight_shipping_remove_data_on_uninstall option to remove those flags too.

Licence

MIT. See LICENSE.