Wrong discount calculation when using multiple fixed discount cart rules

[tiagosampaio]

Preconditions (*)

1. I believe that this happens to any Magento version but I'm using 2.3.7 Commerce Edition currently
2. Create two products with the base price of $19.00 each. Both products must be available to be purchased in the front store.
3. Create two cart discount rules
4. The first cart rule will apply a fixed discount amount of $10.00 to the whole cart. Define a specific coupon code to activate this rule in the shopping cart
5. The second cart rule will apply a fixed discount amount of $18.00 to only one of the products in the cart. This cart rule must be applied automatically to the customer's cart
6. Both cart rules must be active

Steps to reproduce (*)

1. Go to the front store and add the two products in the cart, each one with the price of $19.00 (total $38.00)
2. Go to the cart
3. You should be able to see the second rule already applied and a discount of $18.00 must be visible.
4. In the shopping cart, apply the coupon code to activate the fixed $10.00 discount rule in the cart.
5. You'll be able to see the total discount applied is $24.00 while it should be $28.00
6. The cart total is shown as $14.00 but the correct value should be $10.00

Expected result (*)

1. The discount amount should be $28.00 in total.

Actual result (*)

1. Only a $24.00 discount is applied.

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[m2-assistant]

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[m2-assistant]

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[engcom-Oscar]

Hi @tiagosampaio ! Thank you for your report.
Unfortunately, we are not able to reproduce the issue. May you please update description and add more detailed steps to it, like exact rules configuration?
After following steps from the ticket, we got next result:

[tiagosampaio]

1 - Create two products with the price of $19 each (SKUs: test-product-one, test-product-two).
2 - Create two Cart Price Rules:

The first rule is applied only to the product test-product-two (filtered in the actions section)
Applies a fixed discount of $18 on the product's price.

Configuration:

{
"salesrule": [
	{
		"rule_id" : 5,
		"name" : "Test Product Two Discount",
		"description" : "",
		"from_date" : "2021-05-07",
		"to_date" : null,
		"uses_per_customer" : 0,
		"is_active" : 1,
		"conditions_serialized" : "{\"type\":\"Magento\\\\SalesRule\\\\Model\\\\Rule\\\\Condition\\\\Combine\",\"attribute\":null,\"operator\":null,\"value\":true,\"is_value_processed\":null,\"aggregator\":\"all\"}",
		"actions_serialized" : "{\"type\":\"Magento\\\\SalesRule\\\\Model\\\\Rule\\\\Condition\\\\Product\\\\Combine\",\"attribute\":null,\"operator\":null,\"value\":\"1\",\"is_value_processed\":null,\"aggregator\":\"all\",\"conditions\":[{\"type\":\"Magento\\\\SalesRule\\\\Model\\\\Rule\\\\Condition\\\\Product\",\"attribute\":\"sku\",\"operator\":\"==\",\"value\":\"test-product-two\",\"is_value_processed\":false,\"attribute_scope\":\"\"}]}",
		"stop_rules_processing" : 0,
		"is_advanced" : 1,
		"product_ids" : null,
		"sort_order" : 0,
		"simple_action" : "by_fixed",
		"discount_amount" : 18.0000,
		"discount_qty" : null,
		"discount_step" : 0,
		"apply_to_shipping" : 0,
		"times_used" : 0,
		"is_rss" : 1,
		"coupon_type" : 1,
		"use_auto_generation" : 0,
		"uses_per_coupon" : 0,
		"simple_free_shipping" : 0,
		"row_id" : 5,
		"created_in" : 1,
		"updated_in" : 2147483647
	}
]}

The second one applies a fixed discount of $10 to the whole cart.

{
"salesrule": [
	{
		"rule_id" : 6,
		"name" : "Ten Dollars to Whole Cart",
		"description" : "",
		"from_date" : "2021-05-07",
		"to_date" : null,
		"uses_per_customer" : 0,
		"is_active" : 1,
		"conditions_serialized" : "{\"type\":\"Magento\\\\SalesRule\\\\Model\\\\Rule\\\\Condition\\\\Combine\",\"attribute\":null,\"operator\":null,\"value\":true,\"is_value_processed\":null,\"aggregator\":\"all\"}",
		"actions_serialized" : "{\"type\":\"Magento\\\\SalesRule\\\\Model\\\\Rule\\\\Condition\\\\Product\\\\Combine\",\"attribute\":null,\"operator\":null,\"value\":\"1\",\"is_value_processed\":null,\"aggregator\":\"all\"}",
		"stop_rules_processing" : 0,
		"is_advanced" : 1,
		"product_ids" : null,
		"sort_order" : 0,
		"simple_action" : "cart_fixed",
		"discount_amount" : 10.0000,
		"discount_qty" : null,
		"discount_step" : 0,
		"apply_to_shipping" : 0,
		"times_used" : 0,
		"is_rss" : 1,
		"coupon_type" : 2,
		"use_auto_generation" : 0,
		"uses_per_coupon" : 0,
		"simple_free_shipping" : 0,
		"row_id" : 6,
		"created_in" : 1,
		"updated_in" : 2147483647
	}
]}

3 - With all set then go to the storefront and add test-product-one and test-product-two to the cart.
4 - Go to the shopping cart page and you'll be able to see the discount of -$18.00 already applied because test-product-two is in the cart.

5 - Apply the coupon code to the cart
6 - Check the discount amount now

The version I used for this testing is Magento Commerce 2.4.2-p1

[tiagosampaio]

@engcom-Oscar any update on this?