Proposal: explicitly declaring resolvers with decorator

class MySecondAttempt(ObjectType):
    name = String()
    age = Int(required=True)
        
    @name.resolver
    def resolve_name(self, ...): ...

    @age.resolver
    def resolve_age(self, ...): ...

Explicit is better than implicit.

The resolvers could have any arbitrary name, and could also be defined before or after the class definition. Resolvers could still be defined using the resolver_ prefix convention if the explicit decorator isn’t used.

[dvndrsn]

I really like the idea of declaring resolvers with a decorator. There are a couple of patterns that are possible tho. A pattern that I stumbled across recently works pretty well for declaring functions alongside their schema definition. Maybe we should do an evaluation of different approaches?

Here’s a type with both default and custom resolvers for fields, using a decorator pattern for declaring custom resolvers and schema at the same time.

class StoryType(graphene.ObjectType):

    class Meta:
        interfaces = (graphene.Node, )
        possible_types = (models.Story, )

    title = graphene.String(description='stuff')
    subtitle = graphene.String()
    description = graphene.String()

    @resolves(graphene.String)
    def published_year(story: models.Story, info: graphene.ResolveInfo) -> str:
        return str(story.published_date.year)

The decorator implementation is pretty simple:

def resolves(field, *args, **kwargs):
    def decorate(resolver_function):
        return field(*args, **kwargs, resolver=resolver_function)

    return decorate

I don’t expect that this would break any of the existing Field API. It also removes the possibility that a resolve_XXX method name could be mistyped - the field and resolver are defined in one go.

The only strange thing about this approach is that it is a little unexpected that we define a function and our decorator replaces that function reference with a reference to an Field object that contains that function reference, but it makes for pretty clean Graphene code. You also can’t use this decorator on a function outside of a your ObjectType class.

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