Returning null for an entity without extensions error property

[cameronmakarchuk]

Hi,

I'm using entities in my federated graph and I'm trying to return null for the entity ('address' in the example), while keeping the entities fields (i.e. 'city', 'state', 'country') non-nullable, like this:

data: {
  user: {
   address: null
  }
}

When I query the subgraph that defines the entity directly (Address subgraph in this example), this is no issue and returns null without trying to resolve the individual fields. But if I do the same query through a different subgraph (i.e. User subgraph) using externalRef and the Address entity, I get null but also the extensions property with the error message of 'Cannot return null for non-nullable field Address.city".

data: {
  user: {
   address: null
  },
"extensions": {
    "valueCompletion": [
      {
        "message": "Cannot return null for non-nullable field Address.city.",
        "path": [
          "user",
          "address",
          "city"
        ],
        "extensions": {
          "code": "INVALID_GRAPHQL"
        }
      }
    ]
  }
}

It's like when going through the externalRef it still tries to resolve the entities fields even though in the referenceResolver I'm returning null early if no record is found, and the address field is nullable.

I thought it was because I didn't have resolvable: false set in the key directive of the externalRef but that didn't make any difference.

Any suggestions on how to do this without also getting the extensions property?

[hayes]

I can't tell for sure can you share more details of your setup?

For the query that fails, what does.the resolver for the address field return, and what does the the resolveEntity in the graph that implements Address get called with, and what does it return?

[cameronmakarchuk]

Yeah for sure, let me see if I can clarify a bit better.

So for this example using User and Address subgraphs, it would look like this:

Address subgraph:

const Address= Builder.objectRef<AddressType>('Address').implement({
	fields: (t) => ({
		city: t.exposeString('city'),
		state: t.exposeString('state'),
		country: t.exposeString('country')),
        }),
})

Builder.asEntity(CardTypes.CardDetails, {
	key: Builder.selection<{ id: string }>('id'),
	resolveReference: async ({ id }) => {

		const databaseRecord = <.... get address record from database>

		if (!databaseRecord) {
			return null;
		}

		return {
			data: databaseRecord,
		};
	},
});

User subgraph:

const Address= Builder.externalRef(
	'Address',
	Builder.keyDirective(Builder.selection<{id: string }>('id'), false),
).implement({
	fields: (t) => ({
		id: t.exposeString('id'),
	}),
});

const User = Builder.prismaObject('User', {
  fields: (t) => ({
        id: exposeString('id'),
        address: t.field({
			type: Address,
			nullable: true,
			resolve: (parent) => {
				const { id } = parent;

				return {
					id,
				};
			},
		}),
       })
})

If I run my user query like:

query User {
   user {
      id,
      address {
          city
      }
  }
}

And there is no databaseRecord found on the Address entity referenceResolver it should return null for address, which it does, but I also get an extensions error object like this:

data: {
  user: {
    id: 12345
    address: null
  },
"extensions": {
    "valueCompletion": [
      {
        "message": "Cannot return null for non-nullable field Address.city.",
        "path": [
          "user",
          "address",
          "city"
        ],
        "extensions": {
          "code": "INVALID_GRAPHQL"
        }
      }
    ]
  }
}

I just can't seem to figure out how to get that extensions field removed from the response.

[hayes]

I think this is just how Federation works, your User graph is returning an Address not null, so at that point the router thinks the User has an address, and failing to load it is an Error.

The way to avoid this is to invert the relation and move the User.address field to the Address sub-graph

[cameronmakarchuk]

Ok thanks for the follow up, that's kind of what I thought. I'll play around with inverting the relation and see if I can make that work. Thanks!

[cameronmakarchuk]

In this example, if I were to do the same query to the Address subgraph directly:

query Address {
   address {
      id,
      city,
  }
}

And the databaseRecord is not found, it would return null without the extensions property as expected like this:

data: {
  address: null,
}

That extensions property only comes back on the response when going through the entity.