I have noticed that there is a flaw with the Crafter that introduces a BC break.
I came to this conclusion whilst watching this video: Knarfy showing Wool recipe in a Crafter
For example, if you have a crafter set up like this:S S XS S XX X X
where S = String, X = disabled slot
it will currently craft wool blocks when spammed with a Redstone signal, since there are at the moment no recipes for any combination of the inputs.
If Mojang were to add, i.e. ropes with the following (shaped/shapeless) recipe:S S XX X XX X X
any contraption using the previously mentioned setup will suddenly craft ropes instead of wool.
My proposed idea for avoiding this is:
Check for toggled slots
If there are any toggled slots, only match shaped recipes that match that shape
The upside of this change is that it not only fixes possible BC breaks, but also it essentially doesn't change the functionality of the Crafter in a gameplay affecting way, whilst future-proofing any automated crafting.
That's how it's supposed to work. Existing farms need to be adapted when there is a new update with a new recipe. If all slots from the first example are filled with string, wool blocks will continue to be crafted; if only two are filled, the hypothetical new/other recipe will be crafted.