ProductRepository fails to load product with camelcase SKU

[maximgubar]

Preconditions

1. Magento 2.1 | 2.2 | 2.3.0-dev
2. PHP 7.1.9
3. MySQL 5.7.19

Steps to reproduce

1. Create a simple product with the camel case sku (for example "Test")
2. Use get() method of \Magento\Catalog\Model\ProductRepository to get this product by sku, and specify the sku in lower case.

Expected result

1. NoSuchEntityException is returned

Actual result

1. Notice: Undefined index: test in /www/magento2/app/code/Magento/Catalog/Model/ProductRepository.php on line 254

[magento-engcom-team]

@maximgubar, thank you for your report.
We've created internal ticket(s) MAGETWO-83383 to track progress on the issue.

[rhoerr]

I can confirm this bug.

It's a regression in 2.2.0, still present as of 2.2.2. The problem was introduced right here: cb3b5d1#diff-ff4893a5628d34910295bae32fbcddfdL241

Specifically, products are cached on ProductRepository by $this->instances[$sku]. Previously, products were loaded and stored using the input value $sku (from ProductRepository->get($sku)). That meant different cases could result in multiple loads, but each load would still work without error.

But now, following the change above, the cache is checked by $sku, but the product is added to it by $product->getSku() (in cacheProduct).

The SQL product load is case-insensitive, but the PHP array key comparison is not. Ergo, the product loads successfully (no NoSuchEntityException exception thrown), but if the case differs, it is not found within $this->instances and you get this undefined index error.