Strict resolvers types + expensive field resolvers

[GraemeF]

Hello! I'm trying to enable strict resolvers types as described in this blog post, but I'm required to return an object with all of the non-nullable fields resolved. Many of my field resolvers are expensive (they go off to another API or data source) and so I want to lazily resolve those fields only if requested, leaning on Dataloader to reduce the amount of work needed.

In other words:

type Query {
  foos: [Foo!]!
}

type Foo {
  id: ID!
  someExpensiveField: String!
}

From my Query.foos resolver I'd like to be able to return some Foo instances that only have an id and not someExpensiveField, and have the Foo.someExpensiveField do the work only if necessary, but the generated types won't allow a partial Foo to be returned.

Is there a nice way to do this without making all fields optional (which wouldn't make sense for my schema)?