[V16.0] sale_discount_display_amount: Wrong discount total calculation on discount included amounts

[PieterPaulussen]

Source: https://github.com/OCA/sale-workflow/blob/50f5707635f93a8b5868e20bbee1726c4063bb9c/sale_discount_display_amount/models/sale_order_line.py#L40C46-L40C60

The implementation of this seems off. Are discounts not always calculated on the amount excluding VAT?

[Atteqany]

You are right. wrong calculation.
Odoo makes the % discount before adding the TAX, but this module calculate the %discount on the amount which includes the TAX

For example: Sale order for a product with a price 100 and 10% discount, Odoo wrote the subtotal 90
So the value of the 10% discount is only 10 because all this are before applying the TAX
but this module made the 10% discount value is 11.50, which means it calculated wrong.
Now, the discount amount which the module display is more than the actual which Odoo counted.