Give sample code to add new features in WooCommerce's built-in importer

php
// Hook into WooCommerce product CSV importer to add custom columns in the importer UI
add_filter('woocommerce_product_importer_parsed_data', 'custom_woocommerce_product_importer_parsed_data', 10, 2);
function custom_woocommerce_product_importer_parsed_data($parsed_data, $data) {
    // Example: Add custom field 'custom_text_field' from CSV column 'custom_text'
    if (!empty($data['custom_text'])) {
        $parsed_data['meta_data'][] = array(
            'key'   => '_custom_text_field',
            'value' => sanitize_text_field($data['custom_text']),
        );
    }
    // Example: Add custom field 'custom_number_field' from CSV column 'custom_number'
    if (!empty($data['custom_number'])) {
        $parsed_data['meta_data'][] = array(
            'key'   => '_custom_number_field',
            'value' => floatval($data['custom_number']),
        );
    }
    return $parsed_data;
}

// Hook to add custom CSV columns headers to the importer UI
add_filter('woocommerce_product_importer_csv_columns', 'custom_woocommerce_product_importer_csv_columns');
function custom_woocommerce_product_importer_csv_columns($columns) {
    $columns['custom_text'] = __('Custom Text', 'your-textdomain');
    $columns['custom_number'] = __('Custom Number', 'your-textdomain');
    return $columns;
}

// Save custom fields after product import/update
add_action('woocommerce_product_import_inserted_product_object', 'custom_save_imported_product_meta', 10, 1);
function custom_save_imported_product_meta($product) {
    $imported_meta_data = $product->get_meta_data();
    foreach ($imported_meta_data as $meta) {
        // Save custom meta keys defined above
        if (in_array($meta->key, array('_custom_text_field', '_custom_number_field'))) {
            $product->update_meta_data($meta->key, $meta->value);
        }
    }
    $product->save();
}

Additional instructions and details for extending the WooCommerce importer with custom fields:

- The filter `woocommerce_product_importer_parsed_data` receives parsed CSV row data and allows injection of additional meta data before product saving. This is where custom field values from CSV columns can be added to the product.
- The filter `woocommerce_product_importer_csv_columns` lets you add new custom columns to the CSV import mapping screen so users can match CSV columns to your custom fields.
- The action `woocommerce_product_import_inserted_product_object` is triggered after each product is created or updated during import, useful to finalize saving the custom metadata.
- Custom meta keys should start with an underscore `_` to be treated as hidden post meta by WordPress conventions unless you want them publicly visible.
- Sanitize and validate data when injecting custom fields to enhance security and data integrity.
- This example handles simple text and number fields, but can be extended to handle serialized data, arrays, or other complex structures depending on the custom meta usage.
- For importing complex custom data like attributes, variations, or custom taxonomies, additional processing will be required beyond this simple meta injection.
- Consider compatibility with WooCommerce versions and test importing workflows to handle edge cases gracefully.