Prevent discount coupons from being applied to attributes

Is there a configuration setting I can change so that discount coupons do not apply to attributes?

I have some products that have attributes, for example custom engraving, the attribute adds certain cost. I don't want the discount coupon to apply to the cost the attribute adds.

Thanks.

Alas, there isn't a setting for this.

Thanks for confirming this. So now on to look for the code to do this...

I just saw there are some settings so that sale/specials do not apply, what is the file that controls this so I can take a look and maybe come up with a solution?

includes > modules > order_total > ot_coupon.php

... but be warned, there's an awful lot of potential headaches lurking in that dusty corner.

I meant the file that has the code for preventing sales/specials from applying to applying to attributes. That doesn't appear to be in the ot_coupon.php file.

There isn't any code for doing this. You'll have to create it.

If you want the coupon to apply to the products, but exclude any uplifts from the attributes then you need to insert yourself where the coupon value is calculated and used, which is in the file I referred to above.