how to reorder (switch) billing address before shipping address

Question

on the onepage checkout I need to reorder the billing address before the shipping address. in fact the logic should be the other way around than it is now. if the shipping address differs from the billing address you should be able to edit it. now you can edit the billing address if it differs from the shipping address. also the billing address should appear on the same "page" as the shipping address. currently step 1 in the magento checkout steps.

how would I do this? maybe there is a plugin for this but I couldn't find one yet.

I attached a screenshot of a german shop doing it like this:

I found the .html template file for the billing form and it seems this is the place where it ends up in the checkout_index_index.xml:

<item name="billing-step" xsi:type="array">
    <item name="component" xsi:type="string">uiComponent</item>
    <item name="sortOrder" xsi:type="string">2</item>
    <item name="children" xsi:type="array">
        <item name="payment" xsi:type="array">
            <item name="component" xsi:type="string">Magento_Checkout/js/view/payment</item>
            <item name="config" xsi:type="array">
                <item name="title" xsi:type="string" translate="true">Payment</item>
            </item>
            <item name="children" xsi:type="array">
                <!-- ... -->
                <!-- merge your payment methods here -->
                <item name="afterMethods" xsi:type="array">
                    <item name="component" xsi:type="string">uiComponent</item>
                    <item name="displayArea" xsi:type="string">afterMethods</item>
                    <item name="children" xsi:type="array">
                        <!-- merge additional data after payment methods here -->

<!-- I think here the billing form ends up -->

                    </item>
                </item>
            </item>
        </item>
    </item>
</item>

But it's not specifically placed here and I can't seem to find another place where it is injected to that place.

Answer 1

As Aaron pointed out the form is added in Magento/Checkout/Block/Checkout/LayoutProcessor.php. With this information I developed a module with an after plugin that hooks onto that processor:

app/code/<vendor>/<module>/Model/Checkout/LayoutProcessorPlugin.php

<?php

namespace <vendor>\ReorderBillingForm\Model\Checkout;

class LayoutProcessorPlugin
{

    /**
     * @param \Magento\Checkout\Block\Checkout\LayoutProcessor $subject
     * @param array $jsLayout
     * @return array
     */

    public function afterProcess(
        \Magento\Checkout\Block\Checkout\LayoutProcessor $subject,
        array $jsLayout
    )
    {
        // get billing address form at billing step
        $billingAddressForm = $jsLayout['components']['checkout']['children']['steps']['children']['billing-step']['children']['payment']['children']['afterMethods']['children']['billing-address-form'];

        // move address form to shipping step
        $jsLayout['components']['checkout']['children']['steps']['children']['shipping-step']['children']['billing-address-form'] = $billingAddressForm;

        // remove form from billing step
        unset($jsLayout['components']['checkout']['children']['steps']['children']['billing-step']['children']['payment']['children']['afterMethods']['children']['billing-address-form']);

        return $jsLayout;
    }
}

app/code/<vendor>/<module>/etc/module.xml

<?xml version="1.0" ?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <module name="<vendor>_<module>" setup_version="1.0.0"/>
</config>

app/code/<vendor>/<module>/etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Checkout\Block\Checkout\LayoutProcessor">
        <plugin name="reorder-billing-form"
                type="<vendor>\<module>\Model\Checkout\LayoutProcessorPlugin" sortOrder="<yourOrder>"/>
    </type>
</config>

app/code/<vendor>/<module>/registration.php

<?php

\Magento\Framework\Component\ComponentRegistrar::register(
    \Magento\Framework\Component\ComponentRegistrar::MODULE,
    '<vendor>_<module>',
    __DIR__
);

This successfully reorders the billing address form (and hopefully saves some headaches for other people). But there is still work needed on the javascript(?) that handles the billing address is the same as shipping address mechanism. As this still works the "standard" way.

Additional info:

I saw that in the backend if you create a new order the layout is exactly as wanted. The billing form is "before" the shipping form and the logic is the other way around too. If I can find the time I think it might be beneficial to look at the code there. Maybe it is possible to use it in frontend too.

Answer 2

The error Undefined index: billing-address-form in LayoutProcessorPlugin.php occurs when you have the checkout property "Display Billing Address On" set to "Payment Method" instead of "Payment Page".

Fix with:

UPDATE core_config_data SET VALUE = 1 WHERE path = 'checkout/options/display_billing_address_on';

I would have preferred to add this as a comment to DarsVaedas post (see above), but I don't seem to have the permission …