Create a WooCommerce product attribute programatically

create-attribute.php

<?php
// return;
add_action('init', function() {
	$attribute_name = 'New a';
    $attribute_id = 'new_a';//wc_attribute_taxonomy_id_by_name($attribute_name);
    $attribute_slug = wc_attribute_taxonomy_name($attribute_id);//wc_attribute_taxonomy_id_by_name($attribute_name);
/*
 *     @type int    $id           Unique identifier, used to update an attribute.
 *     @type string $name         Attribute name. Always required.
 *     @type string $slug         Attribute alphanumeric identifier.
 *     @type string $type         Type of attribute.
 *                                Core by default accepts: 'select' and 'text'.
 *                                Default to 'select'.
 *     @type string $order_by     Sort order.
 *                                Accepts: 'menu_order', 'name', 'name_num' and 'id'.
 *                                Default to 'menu_order'.
 *     @type bool   $has_archives Enable or disable attribute archives. False by default.
 */
	if (! taxonomy_exists($attribute_slug)) {
	    $taxonomy_id = wc_create_attribute( [
			'id'   => $attribute_id,
			'name' => $attribute_name,
			'slug' => $attribute_slug,
	    ] );
	} else {
		$taxonomy_id = wc_attribute_taxonomy_id_by_name($attribute_id);
	}
	$attribute = wc_get_attribute($taxonomy_id);

	if (! $attribute || is_wp_error($attribute)) {
		return;
	}


    $pa = new \WC_Product_Attribute();
    $pa->set_id($taxonomy_id);
    $pa->set_name($attribute_slug);
    $pa->set_visible(false);
    $pa->set_options(['Test 4']);
    $product = wc_get_product(8814);
    $product->set_attributes( [ $pa ] );
    $product->save();
	// die;
});