7 replies

Tagged union with one union type having no fields

AshGraphQL

Ash✅Solved

I have a tagged union that looks something like this:

defmodule Foo
  use Ash.Type.NewType,
    subtype_of: :union,
    constraints: [
      types: [
        a: [
          type: TypedStructA,
          tag: :type,
          tag_value: "a"
        ],
        b: [
          type: TypedStructB,
          tag: :type,
          tag_value: "b"
        ],
        c: [
          type: TypedStructC,
          tag: :type,
          tag_value: "c"
        ]
      ],
    ]
end

defmodule Foo
  use Ash.Type.NewType,
    subtype_of: :union,
    constraints: [
      types: [
        a: [
          type: TypedStructA,
          tag: :type,
          tag_value: "a"
        ],
        b: [
          type: TypedStructB,
          tag: :type,
          tag_value: "b"
        ],
        c: [
          type: TypedStructC,
          tag: :type,
          tag_value: "c"
        ]
      ],
    ]
end

But the "c" part of the union has no attributes beyond just the "type". So,

TypedStructC

TypedStructC

winds up with no fields... and then graphql borks on trying to generate a type for it (even if I put all the gql callbacks for naming those types). I kind of see why this is hard to overcome—because graphql doesn't support empty object types, we just don't have a clear way to generate a type for that case of the union, and yet graphql needs something to go in the union. What I'm wondering is if it could make sense for ash_graphql to just always include the tag/discriminator field in the generated type for each union case.

Solution

Hmm...typically you'd make the type actually also have that field then

Jump to solution

Ash Framework•5w ago•

7 replies

Jesse Williams

Tagged union with one union type having no fields

AshGraphQL

Ash✅Solved

I have a tagged union that looks something like this:

defmodule Foo
  use Ash.Type.NewType,
    subtype_of: :union,
    constraints: [
      types: [
        a: [
          type: TypedStructA,
          tag: :type,
          tag_value: "a"
        ],
        b: [
          type: TypedStructB,
          tag: :type,
          tag_value: "b"
        ],
        c: [
          type: TypedStructC,
          tag: :type,
          tag_value: "c"
        ]
      ],
    ]
end

defmodule Foo
  use Ash.Type.NewType,
    subtype_of: :union,
    constraints: [
      types: [
        a: [
          type: TypedStructA,
          tag: :type,
          tag_value: "a"
        ],
        b: [
          type: TypedStructB,
          tag: :type,
          tag_value: "b"
        ],
        c: [
          type: TypedStructC,
          tag: :type,
          tag_value: "c"
        ]
      ],
    ]
end

But the "c" part of the union has no attributes beyond just the "type". So,

TypedStructC

TypedStructC

Solution

Hmm...typically you'd make the type actually also have that field then

Jump to solution

Tagged union with one union type having no fields

Tagged union with one union type having no fields

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