Cart / Checkout: Autoship Free Shipping on Orders over $50

In this example the merchant wants to only offer the Autoship Free Shipping option at checkout, when there are Autoship Items in the Cart and the Cart total is $50 or more. 

Example:

/**
 * Calculate the total amount in cart for Autoship Items.
 * @param array $cart Optional. The cart to process.
 * @return float The total $ amount
 */
function xx_calculate_cart_autoship_total( $cart = NULL ){

	$autoship_total = 0;
	$cart = isset( $cart ) ? $cart : WC()->cart->get_cart();
  
	// Get the cart content total for Autoship products
	foreach( $cart as $cart_item ){
	  // Sum total autoship amount
	  if ( isset( $cart_item['autoship_frequency_type'] ) && isset( $cart_item['autoship_frequency'] ) ) {
		$autoship_total += $cart_item['line_total'];
	  }
	}
	return $autoship_total;
  
  }
  
  /**
   * Adjust the available Shipping Rates by removing Autoship Free Shipping
   * when the total autoship amount is less then $50
   *
   * @param array An array of Available WC_Shipping_Rate Objects.
   * @param array $package Package of cart items.
   * @return array The filtered array of WC_Shipping_Rate Objects
   */
  function xx_disable_free_shipping_on_autoship_amount( $rates, $package ){
  
	// Get the Autoship Total
	$autoship_total = xx_calculate_cart_autoship_total();
  
	// Disabling Autoship Free Shipping Method based on Autoship Amount
	if( $autoship_total < 50 ){
	  foreach ( $rates as $rate_key => $rate ){
		if( 'autoship_free_shipping' == $rate->method_id )
		unset( $rates[ $rate_key ] );
	  }
	}
  
	return $rates;
  
  }
  add_filter('woocommerce_package_rates', 'xx_disable_free_shipping_on_autoship_amount', 10, 2 );

Now, the free shipping option only displays when the $50 minimum subtotal is reached.