I want to programmatically update the quantity of a bundle option of a item in the users cart.

Currently in the cart, a bundle with the option “12 x DIN A4 page”.

This is what I have done so far

/** @var \Magento\Quote\Model\Quote\Item */ protected $  quoteItem;  public function updateNumberOfPages($  pages) {     $  qtyOptions = $  this->quoteItem->getQtyOptions();     assert(count($  qtyOptions) == 1);     $  option = reset($  qtyOptions);      $  qty = $  pages * $  this->getNumberOfCopies();     $  this->quoteItem->updateQtyOption($  option, $  qty);     $  this->quoteItem->save($  this);      $  this->quoteItem->getQuote()->setTotalsCollectedFlag(true)->collectTotals();      return $  this; } 

So I call this function updateNumberOfPages(4);

A bit later in the same request, I want to fetch and the new totals:

/** @var \Magento\Quote\Api\CartTotalRepositoryInterface */ protected $  cartTotalsRepository;  ...  $  totals = $  this->cartTotalsRepository->get($  quoteItem->getQuoteId()); 

But here, the just updated item still reports “12 x DIN A4 page” – even I have set the qty above to 4.

What is going wrong?

Bonus question: $ this->quoteItem->save() is deprecated – what to use instead?