WordPress action to sync stock quantity to connected sites with the WooCommerce Stock Synchronization plugin when using WP All Import to update stock on the master shop.

wpai-wcss-sync-stock.php

<?php
// Add below code to functions.php of your WordPress theme.

/**
 * Sync stock with WooCommerce Stock Synchronization after WP All Import product update.
 *
 * @see https://www.pronamic.eu/plugins/woocommerce-stock-synchronization/
 */
function wcss_pmxi_stock_update( $post_id ) {
	if ( ! is_callable( 'wc_get_product' ) ) {
		return;
	}

	$product = wc_get_product( $post_id );

	if ( ! $product ) {
		return;
	}

	if ( $product->is_type( 'variation' ) ) {
		do_action( 'woocommerce_variation_set_stock', $product );
	} else {
		do_action( 'woocommerce_product_set_stock', $product );
	}
}

add_action( 'pmxi_saved_post', 'wcss_pmxi_stock_update', 10, 1 );

// The WP All Import - WooCommerce Add-On Pro adds the `pmwi_pmxi_after_post_import` action,
// which removes all action hooked into `shutdown`. WooCommerce Stock Synchronization uses
// the shutdown action to sync. We therefore remove the `pmwi_pmxi_after_post_import` action.
function remove_pmwi_pmxi_after_post_import() {
	remove_action( 'pmxi_after_post_import', 'pmwi_pmxi_after_post_import' );
}

add_action( 'pmxi_after_post_import', 'remove_pmwi_pmxi_after_post_import', 1 );