Cart Sales Rule with negated condition over special_price does not work for configurable products

[Filipe-Bicho]

Preconditions

1. magento 2.2.3
2. php 7.1.10
3. mariadb 10.1.24

Steps to reproduce

0. Setup vanilla 2.2.3 with demodata (or use a similar existing store)
1. Enable the special_price for promo rule conditions:
   1. Stores > Attributes > Product
   2. Search for and edit special_price
   3. Storefront Properties: Use for Promo Rule Conditions: Yes
   4. Save
2. create new cart sales rule:
   1. Marketing > Cart Price Rules
   2. Add New Rule:
      1. Rule name = "Special Price Test"
      2. Website: select all
      3. Customer Groups: select all
      4. Coupon: "Specific Coupon"
      5. Coupon Code: "special"
      6. Actions: Discount Amount: "10"
      7. Actions: Apply the rule only to cart items matching the following conditions: "if ALL of these conditions are FALSE": "Special Price greater than 0.01"
      8. Leave all other fields to their defaults and save
3. In the front end, add a the child product of a configurable product to the cart, such that the child product has a special price set. This product should be the only one in the cart.
4. "View and Edit Cart" > "Apply Discount Code": special

Expected result

1. the coupon is not accepted with the message The coupon code "special" is not valid.
2. no discount is applied

Actual result

1. the coupon is accepted with the message You used coupon code "special".
2. a discount is applied

The intention with the above mentioned sales rule is to exclude already discounted products from further discounting via a coupon code.

[ktruehl]

The problem manifests itself in the rule validation mechanism. For configurable products both the associated and the parent product is handed to the validate() method in Magento\Rule\Model\Condition\Product\AbstractProduct. But for special prices the special_price attribute is not defined. So in validate() in Magento\Rule\Model\Condition\AbstractCondition the call $model->getData($this->getAttribute()) will always return null for the parent product and thus validate to false. Thus price rule conditions using the special_price attribute will always validate to false for configurable products.

We have created a quickfix for this issue: bugfix-GH11178-configurable_product_sales_rule_special_price_validation.2018-02-06.diff.zip. It is only that, i.e. a quickfix. A more comprehensive fix would be to check Magento\Rule\Model\Condition\Product\AbstractProduct::validate() whether an attribute is defined at all for a specific product, and if not, to validate to true.

[magento-engcom-team]

@Filipe-Bicho, thank you for your report.
We've acknowledged the issue and added to our backlog.

[sunilit42]

I am working on this at #dmcdindia

[novikor]

#kiev-cd