buildFederatedSchema with existing GraphQLSchema

I’m trying to implement apollo-federation in type-graphql library which uses GraphQL*Type to construct schemas. Is it possible to build convert/build a federated schema from a GraphQLSchema? It seems like these libraries will have to convert to outputting SDL instead of using graphql-js directly.

[j]

@JacksonKearl Hey! I started hacking at it and got type-graphql to output a federation type of schema.

The directive hack is here: https://github.com/19majkel94/type-graphql/pull/369/files#diff-48f4a1f7b529a17d4579df20f8af7af1R272

And here’s a quick test showing that it works (well prints schema correctly): https://github.com/19majkel94/type-graphql/pull/369/files#diff-b0c36f08a566dd0298fff8e07447781b

I mimic’d the demo reviews service.

I’m not sure if I break schema by using astNode instead of extensionASTNodes. I’d think I should use extensionASTNodes but apollo federation doesn’t pull directives unless astNode IS defined and using typescript, I can’t have it be an empty object (https://github.com/apollographql/apollo-server/blob/master/packages/apollo-federation/src/service/printFederatedSchema.ts#L170).

That directive issue you listed is so people can use directives more as middleware / validation / etc, whereas I believe federation just uses them for referencing schema and doesn’t do anything on a resolver level with them? So I thought I could implement them directly for now to see if I can get it to work. I believe I could create a __resolveReference field resolver within type-graphql, so

I’m not too sure where to go from here though, haha. I was going about it the “manual” way you mentioned instead of using the buildFederatedSchema route.

/cc @19majkel94

[MichalLytek]

It looks like the only difference between type-graphql’s ResolversMap and our GraphQLResolverMap is the addition of a top-level “ResolverOptions” construct on their side. I’m not quite sure what that does, but if we can just filter it out the types should be identical.

@JacksonKearl type-graphql’s ResolversMap is designed to work with other tools, like graphql-tools - I’ve basically copied their types and refactored them a bit. The ResolverOptions are responsible for handling subscribe instead of resolve (not supported in federation) as well as __resolveType and __isTypeOf for unions and interfaces.