executeOperation: Support TypedDocumentNode generic type

[jangerhofer]

Howdy, @glasser?

As @tobiasdiez (among others) commented, ApolloServer.executeOperation support for the TypedDocumentNode format¹ would advance type-safety for all who use graphql-code-generator alongside integration tests. I see that you both made executeOperation generic over the TypedQueryDocumentNode type from graphql-js in #6960 and considered TypedDocumentNode support around the same time. If I am not mistaken, such support never landed!

I am eager to take a stab at making apollo-server play nicely with the graphql-code-generator standard in tests, but want to check

(a) that you're still in favor of this change 😄 and

(b) whether you have any particular opinion about how to approach implementation.

Are you willing to offer guidance?

Footnotes

1. Specifically, support for inferring the variables parameter & return type of executeOperation based on the type of the GQL document passed as the query parameter. ↩

[trevor-scheer]

@jangerhofer go for it, that'd be great! Happy to offer guidance as needed.

Presumably adding TypedDocumentNode to the union type for request.query (the argument to executeOperation) should work. As far as I can tell it should just be a compatible addition with no runtime changes needed.

Some tests which show the type correctness of using a TypedDocumentNode would be great.

[jangerhofer]

Awesome -- thanks @trevor-scheer! I'll circle back with a diff soon.