commerce-8.x-2.8/modules/tax/commerce_tax.module

<?php

/**
 * @file
 * Provides tax functionality.
 */

use Drupal\commerce_tax\TaxableType;
use Drupal\Core\Entity\EntityTypeInterface;
use Drupal\Core\Field\BaseFieldDefinition;
use Drupal\Core\Form\FormStateInterface;

/**
 * Implements hook_entity_base_field_info().
 */
function commerce_tax_entity_base_field_info(EntityTypeInterface $entity_type) {
  if ($entity_type->id() === 'commerce_store') {
    $fields['prices_include_tax'] = BaseFieldDefinition::create('boolean')
      ->setLabel(t('Prices are entered with taxes included.'))
      ->setDisplayOptions('form', [
        'type' => 'boolean_checkbox',
        'settings' => [
          'display_label' => TRUE,
        ],
        'weight' => 3,
      ])
      ->setDisplayConfigurable('view', TRUE)
      ->setDisplayConfigurable('form', TRUE)
      ->setDefaultValue(FALSE);

    $fields['tax_registrations'] = BaseFieldDefinition::create('list_string')
      ->setLabel(t('Tax registrations'))
      ->setDescription(t('The countries where the store is additionally registered to collect taxes.'))
      ->setCardinality(BaseFieldDefinition::CARDINALITY_UNLIMITED)
      ->setSetting('allowed_values_function', ['\Drupal\commerce_store\Entity\Store', 'getAvailableCountries'])
      ->setDisplayOptions('form', [
        'type' => 'options_select',
        'weight' => 4,
      ])
      ->setDisplayConfigurable('view', TRUE)
      ->setDisplayConfigurable('form', TRUE);

    return $fields;
  }
}

/**
 * Implements hook_form_BASE_FORM_ID_alter() for 'commerce_store_form'.
 */
function commerce_tax_form_commerce_store_form_alter(&$form, FormStateInterface $form_state) {
  if (isset($form['prices_include_tax']) || isset($form['tax_registrations'])) {
    $form['tax_settings'] = [
      '#title' => t('Tax settings'),
      '#weight' => 99,
      '#type' => 'details',
      '#collapsible' => TRUE,
      '#open' => TRUE,
    ];
    $form['prices_include_tax']['#group'] = 'tax_settings';
    $form['tax_registrations']['#group'] = 'tax_settings';
  }
}

/**
 * Implements hook_form_FORM_ID_alter() for 'commerce_order_item_type_form'.
 */
function commerce_tax_form_commerce_order_item_type_form_alter(array &$form, FormStateInterface $form_state) {
  /** @var \Drupal\commerce_order\Entity\OrderTypeInterface $order_item_type */
  $order_item_type = $form_state->getFormObject()->getEntity();

  $form['commerce_tax'] = [
    '#type' => 'container',
    '#weight' => 5,
  ];
  $form['commerce_tax']['taxable_type'] = [
    '#type' => 'select',
    '#title' => t('Taxable type'),
    '#options' => TaxableType::getLabels(),
    '#default_value' => $order_item_type->getThirdPartySetting('commerce_tax', 'taxable_type', TaxableType::getDefault()),
    '#required' => TRUE,
  ];
  $form['actions']['submit']['#submit'][] = 'commerce_tax_order_item_type_form_submit';
}

/**
 * Submission handler for commerce_tax_form_commerce_order_item_type_form_alter().
 */
function commerce_tax_order_item_type_form_submit($form, FormStateInterface $form_state) {
  /** @var \Drupal\commerce_order\Entity\OrderTypeInterface $order_item_type */
  $order_item_type = $form_state->getFormObject()->getEntity();
  $settings = $form_state->getValue(['commerce_tax']);
  $order_item_type->setThirdPartySetting('commerce_tax', 'taxable_type', $settings['taxable_type']);
  $order_item_type->save();
}