Default_value option in Arguments inside Mutation is not working as expected about graphene HOT 2 OPEN

Hey @VicGoico, from my point of view, this is not a bug but expected behavior. Default values should be treated as READ-Only. We cannot expect all default values to implement copy to satisfaction. Due to that, it is on the user to avoid mutating the defaults. My recommendation for lists: use an empty tuple for defaults (,). However, documentation could be improved to mention this.

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Hi @erikwrede , thanks for your answer.

Therefore, the solution is to use .copy(), when we want to handle the value argument, to isolate it.

To sum up, the example that I mentioned, will work fine doing this:

class AnimalFarm(graphene.Mutation):
    class Arguments:
        animals = graphene.List(graphene.String, default_value=(,))

    output = graphene.List(graphene.String)

    def mutate(root, info, **filters):
        animals_mio = filters["animals"].copy() # Here is the solution
        animals_mio.append('duck')
        
        return animals_mio


class Mutation(graphene.ObjectType):
    animal_farm = AnimalFarm.Field()

Any mantainer can close the issue if they see it necessary.

Thanks for your work and have a nice day

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