Validation on required attributes when updating a product on the REST API doesn't check the attribute set of the product.

[alexgmin]

Preconditions

1. Magento 2.1.2
2. PHP 5.6
3. MySQL 5.7

Steps to reproduce

1. Create two attribute sets.
2. Create a required attribute
3. Assign the attribute to the first attribute set, but not the second.
4. Create two products, one for each attribute set.
5. Try to update the product on the attribute set without the required attribute with the REST API without that attribute.

Expected result

1. The product is updated and nothing complains about the required attribute, since is not required for the attribute set of the product.

Actual result

1. Magento doesn't check the attribute set of the product when using the API, so it throws an exception complaining about the missing attribute.
   "message": "The value of attribute \"foo"\ must be set",

The process works normally when doing it on the backend, but on the API, it doesn't check the attribute set of the product, only the the entity_type.

[RomanKrut]

@alexgmin Hi, thank you for your feedback. Can you add more information with body of requests and examples?

[springerin]

Having the same issue on magento 2.1.7 ( with sample data). The problem is from
vendor/magento/module-eav/Model/Entity/AbstractEntity.php:592 public function walkAttributes($partMethod, array $args = [], $collectExceptionMessages = null) that loads also attributes that are not part of the attribute set and so if they are required but not part of the attribute set they still give the error in the validation process.