Index WooCommerce Product Variation SKUs in SearchWP.

searchwp-customizations.php

<?php

// @link https://searchwp.com/documentation/knowledge-base/woocommerce-product-variation-skus/
// Index WooCommerce Product Variation SKUs alongside the parent Product.
add_filter( 'searchwp\entry\data', function( $data, \SearchWP\Entry $entry ) {
	$entry = $entry->native();

	if ( ! $entry instanceof \WP_Post || 'product' !== get_post_type( $entry ) ) {
		return $data;
	}

	// The 'extra' meta_key we'll use to store these SKUs.
	$product_variation_key = 'swp_wc_product_variation_sku';

	// Retrieve all Product Variations.
	$product_variations = get_posts( [
		'post_type'   => 'product_variation',
		'nopaging'    => true,
		'fields'      => 'ids',
		'post_parent' => $entry->ID,
	] );

	if ( empty( $product_variations ) ) {
		return $data;
	}

	$product_variation_skus = [];

	foreach ( $product_variations as $product_variation ) {
		$product_variation_skus[] = get_post_meta( $product_variation, '_sku', true );
	}

	$data['meta'][ $product_variation_key ] = new \SearchWP\Tokens( array_filter( $product_variation_skus ) );

	return $data;
}, 20, 2 );

// Add 'extra' meta_key as available option.
add_filter( 'searchwp\source\attribute\options', function( $keys, $args ) {
	if ( $args['attribute'] !== 'meta' ) {
		return $keys;
	}

	// This key is the same as the one used to store the Product Variation SKUs
	// in the searchwp\entry\data hook above, they must be the same.
	$product_variation_key = 'swp_wc_product_variation_sku';

	// Add "Product Variation SKUs" Option if it does not exist already.
	if ( ! in_array(
		$product_variation_key,
		array_map( function( $option ) { return $option->get_value(); }, $keys )
	) ) {
		$keys[] = new \SearchWP\Option( $product_variation_key, 'Product Variation SKUs' );
	}

	return $keys;
}, 20, 2 );