gqlgen struct marshalers generate "null" for pointer fields that are optional

[jwatte]

What happened?

I have:

type Foo {
    a: String
    b: String
}

and this maps to go struct:

type Foo struct {
    A *string
    B *string
}

and I return an instance of this, with "A" set and "B" nil

What did you expect?

I expect to get a GQL entity as follows:

{
    a: "value"
}

What I actually get:

{
    a: "value",
    b: null
}

I would expect optional parameters that have nil values to not be returned at all -- they are optional.

This means that it's impossible to represent "this thing doesn't exist" and you cannot implement a discriminated union (other than the very clunky interface-based method.)

Minimal graphql.schema and models to reproduce

type Foo {
    a: String
    b: String
}
query {
    getFoo: Foo
}

type Foo struct {
    A *string
    B *string
}

func (r *queryResolver) GetFoo(ctx context.Context) (*model.Foo, error) {
    str := "foo"
    return &model.Foo{A: &str}, nil
}

versions

• go run github.com/99designs/gqlgen version?
  v0.17.2

• go version?
  go version go1.16.11 linux/amd64