magento/magento2#40302: TypeError in Creditmemo\Validation\QuantityVa…

[shmVan]

Fix PHP 8.4 TypeError when credit memo quantity passed as string

• Cast quantity to float before passing to isValidDecimalRefundQty()
• Add test cases for string quantity values from API
• Ensure PHP 8.4 compatibility with strict types

Description (*)

This PR fixes a PHP 8.4 compatibility issue in credit memo quantity validation that causes a TypeError when quantity values are passed as strings from API/JSON requests.

Problem:
When creating a credit memo via API where the quantity is provided as a string (e.g., "1.0" or "2.5"), PHP 8.4's strict type enforcement throws a TypeError in QuantityValidator::isValidDecimalRefundQty() because the
method signature requires a float parameter but receives a string.

Root Cause:

• The method isValidDecimalRefundQty() has strict type declaration: float $itemQty
• API/JSON input often deserializes numeric values as strings
• $item->getQty() can return string values depending on the data source
• PHP 8.4 enforces strict types more rigidly than previous versions

Solution:
Added explicit (float) type cast when passing $item->getQty() to isValidDecimalRefundQty() method on line 136. This approach:

• Follows existing Magento patterns (similar implementation in InvoiceService::setInvoiceItemQuantity())
• Maintains compatibility with declare(strict_types=1)
• Ensures proper type handling regardless of input source
• Does not break backward compatibility

Testing:
Added two new test cases in QuantityValidatorTest to verify:

1. String quantity "1.0" for non-decimal products (integer quantities)
2. String quantity "2.5" for decimal-allowed products (float quantities)

All existing tests continue to pass.

Error Fixed:
TypeError: Magento\Sales\Model\Order\Creditmemo\Validation\QuantityValidator::isValidDecimalRefundQty():
Argument #2 ($itemQty) must be of type float, string given

Related Pull Requests

Fixed Issues (if relevant)

1. Fixes [Issue] TypeError in Creditmemo\Validation\QuantityValidator caused by min() with string quantity #40302

Manual testing scenarios (*)

1. Create a new order with at least one product (quantity: 2)
2. Create an invoice for the order
3. Send a POST request to /rest/V1/creditmemo with the following payload: ```json
   {
   "entity": {
   "order_id": <order_id>,
   "items": [
   {
   "order_item_id": <item_id>,
   "qty": "1.0"
   }
   ]
   }
   }
4. Expected result: Credit memo is created successfully without TypeError
5. Without fix: TypeError thrown on QuantityValidator::isValidDecimalRefundQty()

Questions or comments

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)

[m2-assistant]

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[shmVan]

@magento run all tests

[sir1ke]

Note this related PR:
#40303

[engcom-Hotel]

@magento run all tests

[engcom-Hotel]

@magento run all tests

[engcom-Hotel]

Hi @shmVan,

Thank you for this contribution and for the clear description and test. Your change correctly addresses the credit memo quantity issue and is very much appreciated.

After review, we have decided to close this pull request in favour of #40303. That PR takes a slightly broader approach (including the same validation fix plus related handling when the credit memo is built from an invoice).

This is not a reflection on the quality of your work—both directions fix the reported problem; we are standardising on one implementation to avoid duplicate merges.

We are grateful for the time you put into this and for helping highlight the issue. Please do keep contributing; fixes like yours make a real difference to the project.

Thanks again.