Passing data to the checkout

Unlike the mostly static CMS, category, and product pages, the checkout page has a more dynamic nature. It is an application on its own, primarily constructed out of JS components, which further utilize Magento's API endpoints to move us through the checkout steps. Magento's Magento\Checkout\Model\CompositeConfigProvider type allows us to push the necessary server-side information easily to the uiComponent of the storefronts.

A quick lookup for the name="configProviders" string across the content of di.xml in the <MAGENTO_DIR> directory reveals dozen of definitions. A closer look at the <MAGENTO_DIR>/module-tax/etc/frontend/di.xml reveals the following:

<type name="Magento\Checkout\Model\CompositeConfigProvider">
  <arguments>
    <argument name="configProviders" xsi:type="array...