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Union types in connections: 'UnionOptions' object has no attribute 'model'

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
graphql, python, sqlalchemy
Domain
api, backend, database

Research direction

Start with SQLAlchemyConnectionField.wrap_resolve() and its model property, then reproduce the reported query using a Graphene union of SQLAlchemyObjectType classes. Trace how the union's _meta data reaches the connection resolver; done requires defining how connections with multiple underlying models should be handled without the reported UnionOptions.model error.

Written by the indexing model from the issue text.

Description

Are there plans to add support for union types in connections? I have a setup like the following:

class Cat(SQLAlchemyObjectType):
    class Meta:
        model = CatModel
        interfaces = (relay.Node,)

class Dog(SQLAlchemyObjectType):
    class Meta:
        model = DogModel
        interfaces = (relay.Node,)

class Animal(graphene.Union):
    class Meta:
        types = (Cat, Dog)

class Query(graphene.ObjectType):
    animals = SQLAlchemyConnectionField(Animal)

and when I try to query for animals, I get the error: 'UnionOptions' object has no attribute 'model'.

I traced this back to the self.model call in wrap_resolve():

    def wrap_resolve(self, parent_resolver):
        return partial(
            self.connection_resolver,
            parent_resolver,
            get_nullable_type(self.type),
            self.model,
        )
    def model(self):
        return get_nullable_type(self.type)._meta.node._meta.model

When the type is a union, get_nullable_type(self.type)._meta.node._meta returns the union class (in this case Animal). In order to get a model from that, we have to drill down into its types (e.g. get_nullable_type(self.type)._meta.node._meta.types[0]._meta.model) but because it's a union, it will contain multiple models.
Any ideas how to get around this?

Dominant language
Python
Stars
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Forks
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PR merge metrics
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