php - WooCommerce custom stock status -

i trying overwrite woocommerce_product_is_in_stock filter/hook, have found answer: additional stock options in woocommerce

add_filter('woocommerce_product_is_in_stock', 'woocommerce_product_is_in_stock' );  function woocommerce_product_is_in_stock( $is_in_stock ) {     global $product;      // array of custom stock statuses have add cart button     $stock_statuses = array('onrequest','preorder');      if (!$is_in_stock && in_array($product->stock_status, $stock_statuses )) {         $is_in_stock = true;     }      return $is_in_stock; } 

but helps me partway, return product in stock instances whenever try view cart product cannot found. global $product seems "null" whenever var_dump it.

how can change code cart allow me order product own custom stock status?

thanks in advance!

i did updating woocommerce is_in_stock() function in woocommerce -> includes -> abstracts -> abstract-wc-product.php

public function is_in_stock() {      if ( $this->managing_stock() && $this->backorders_allowed() ) {         return true;     } elseif ( $this->managing_stock() && $this->get_total_stock() <= get_option( 'woocommerce_notify_no_stock_amount' ) ) {         return false;     } else {         return $this->stock_status === 'instock'; } 

to

public function is_in_stock() {      $stock_statuses = array('onrequest','preorder');      if ($this->get_total_stock() > get_option( 'woocommerce_notify_no_stock_amount' ) && in_array($this->stock_status, $stock_statuses )) {         return true;     }      if ( $this->managing_stock() && $this->backorders_allowed() ) {         return true;     } elseif ( $this->managing_stock() && $this->get_total_stock() <= get_option( 'woocommerce_notify_no_stock_amount' ) ) {         return false;     } else {         return $this->stock_status === 'instock';     } }