How to Merge guest quote items to customer quote(if customer log in) by magento 2 rest API

[sangeetajain]

Preconditions (*)

Magento 2.3-develop
If any one is add products in cart by guest and after that login then how it will merge guest cart to customer login cart items by Rest API.

Steps to reproduce (*)

1. Create a customer
2. Log out from customer account
3. Add any product to cart
4. Try to merge quotes via API

Authorization -"Bearer {user-token}"
PUT {URL}/rest/V1/guest-carts/{guest-card-id}
Body: 
{
  "customerId": {customer id},
  "storeId": {store id}
}

Expected result (*)

200 OK
true

Actual result (*)

getting error : "The customer can't be assigned to the cart because the customer already has an active cart."

[m2-assistant]

Hi @sangeetajain. Thank you for your report.
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@sangeetajain do you confirm that you were able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
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[m2-assistant]

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[magento-engcom-team]

✅ Confirmed by @engcom-Charlie
Thank you for verifying the issue. Based on the provided information internal tickets MC-21009 were created

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[m2-assistant]

Hi @ivan-koliadynskyy. Thank you for working on this issue.
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[sangeetajain]

Hello Team,
Is there any update regarding this issue...?

[sangeetajain]

Hello Team,
Is there any update regarding this issue...?

[engcom-Charlie]

Hello @sangeetajain !
Fix in progress as you can see in #24862 .

[magento-engcom-team]

Hi @sangeetajain. Thank you for your report.
The issue has been fixed in #24862 by @ivan-koliadynskyy in 2.3-develop branch
Related commit(s):

• 2a6dc66bbeab6179a717f31c988ed0a4eee8ec4d
• dc460c817b810553c3a037f9ae65985a07efb975
• 9f77a81dc7921077a0edd600d18d51a95115d002
• 6ff21a67ba555b2dc24b677a0368085e976a457f
• d0e2ced7c02a04a32de03d6bad0cb06ff8fc431f
• b6f0bb33a648fd1e9014e6fcd93fe019e1e19003
• fe12c41fb92d9ee24f7af529230919cbdb162ba2
• e5095fbae95c4c40f10576da74d86e752fbe5362
• daede858a4838d013c728f2e12d749a233f34b2a
• 08fb9aec1e152181b817a342c55ce6ff2644a55e
• 8b08a513b8bdc65601d6e6556c786350218dc13b

The fix will be available with the upcoming 2.3.4 release.

[dimaportenko]

I created a workaround from the above fix for versions < 2.3.4. https://github.com/troublediehard/plab-cartsmergefix

[anowarsadata]

What need to do for work with magento 2.3.3

[ghost]

The fix is working but the merge is not taking into consideration the available quantity of stock items of the products in cart.
At Model\Quote.php, lines 2392 and 2393:
...
$quoteItem->setQty($quoteItem->getQty() + $item->getQty());
$this->itemProcessor->merge($item, $quoteItem);
...

The setQty bypasses any check of availability / eligibility.
Let's say a product has only 1 item in stock, a logged in customer adds it to the cart, then logs out, adds it again as a guest and then logs back in. The merge will result in 2x items of a 1x stock available product, and the checkout will throw an error, forcing the customer to manually adjust qty in cart.