Allow @hasInverse on union types

Issues GraphQL
,
2

As per GraphQL spec:

GraphQL Unions represent an object that could be one of a list of GraphQL Object types, but provides for no guaranteed fields between those types.

Means, one can’t assume anything about the fields in member types of a union. If there are common fields in two types, then you should be using interfaces in your schema design to represent that abstraction.

Just for counter-example, I can add one more type to the union Bar like this, which doesn’t have a field foo:

type Foo {
   m: [Bar!]!
}

union Bar = Blub | Blabla | MyType

type MyType {
   myField: String
}

type Blub {
   foo: Foo!
}

type Blabla {
   foo: Foo!
}

The schema is still valid GraphQL, but now you can’t really apply @hasInverse because there is no field named foo in type MyType.

So, @hasInverse doesn’t make semantic sense with unions.

1 Like