With sincere gratitude from Webel IT Australia to Drupal CMS. Although it's not perfect, it is very powerful and is very popular with good reason.
At the time of writing, because Drupal Commerce does not yet have an official action for preventing addition of incompatible product items to a cart, one needs to use one of a number of tricks to handle cases of incompatible products.
Usually these involve looping over all items in a cart, detecting incompatibilities, and then removing them "after the fact", which has many disadvantages (such as the need for a message saying something has been removed from a cart and why, immediately after a message has been issued telling users an item was added to the cart, not an idea user experience).
The best starting point (one that handles many cases) is this video from Randy Fay: .
This educational site is brought to you by Webel IT Australia, experts in database-driven web technology for industry, engineering, education and science. Webel is one of Australia's most experienced Drupal CMS web site specialists.
'It ain't necessarily so,
It ain't necessarily so,
The t'ings dat yo' li'ble,
To read in de [Drupal6/7] Bible,
It ain't necessarily so.'
Heresy: Doctrine rejected as false by religious authorities.
Logical fallacy: Appeal to popularity, Argumentum ad populum.
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