[Enhancement] Allow mixing into all subclasses of a class

[1101-Grills-Oren]

Here is my suggestion: make a variant of @mixin that will apply each injection not only to the class that the mixin is targeting, but also all classes that extend or implement it.

This would allow things such as:
Better mod compatibility (behavior that is overridden by a class would also get the mixin and so no code gaps from that)
Easier mass mixins (its kinda annoying to make a mixin for EVERY vanilla class that extends Item.java that overrides a specific method)

I think it would also be best if the mixin only threw an error on the main class and not any subclasses, but leave an error in the logs. That way, weird overrides would not crash the game.

If you do not want to do it, I will make a mod myself that implements the mentioned functionality.

[Nischhelm]

ive done that in https://github.com/Nischhelm/EnchantmentControl by applying ASM onto my mixin classes and just as llamalad prophecised in the mixin discord channel it was a huge pain with a lot of unexpected gotchas.

the issue was mostly

• remapping
• and the early/late distinction (that might not be present in newer versions of mc? im in forge 1.12.2 and there it is an issue), where some modded classes are loaded early anyway, if some coremod loads them early

but theres also real implementation questions like: do you always want to override overriden behavior or do you sometimes also want to allow/prioritise that overriden behavior? then you have to treat the original class differently than the child classes... ive had to do that for canApply and canApplyAtEnchantingTable in EnchantmentControl.