Fix _service { sdl } render to hide federated fields

[kdawgwilk]

While implementing this PR apollographql/apollo-federation-subgraph-compatibility#35 I found we are not filtering federated schema fields from the SDL render like we should

[kdawgwilk]

This was reverted in #29 and we need to look at taking a different approach

[kzlsakal]

Reopening this since #42 was reverted by #48

[lorgio-jimenez]

Is there a version of the library that does render this properly? We're switching over from using a mesh server to using this library, and this is a serious blocker for us to deploy with.

[kzlsakal]

Is there a version of the library that does render this properly?

The SDL rendered with v0.2.4 is compliant with Gateway 2 and it works without any problems. We currently use it in production.

The issue is about full compliance with Apollo Federation specs. Rendering these extra fields in the SDL doesn't affect the functionality as far as I can tell.

To answer your question though, unfortunately, we do not have a version where this issue is fixed without introducing bugs like #47 or #28.

[kzlsakal]

While looking at this, I noticed that there might have been an update on Apollo Federation docs. It mentions:

Unlike introspection, the sdl field's returned string includes federation-specific directives like @key.

https://www.apollographql.com/docs/federation/subgraphs/#query_service

This may be implying that we don't need to omit federation-specific fields from the SDL render after all. Any thoughts @kdawgwilk?

[kdawgwilk]

You are supposed to include the directives themselves on each field but it's the federated type definitions that are not recommended to be present eg union _Entity or directive definitions. Absinthe does a few optimizations like eagerly stripping out types that are not referenced in any accessible way in the schema which has been causing us problems. We have a pretty good trade off in place right now that should work great. What issues are you running into?

[kroehre]

_resolveReference fields are appearing in the schema also

[kdawgwilk]

@kzlsakal we could prob strip out those _resolveReference fields no matter what even if there is no _Entity type

[kdawgwilk]

This PR will strip out the _resolveReference fields from the SDL render #55 which helps to partially resolve this issue

[dariuszkuc]

FYI federation v1 required SDL modifications to strip out the fed definitions but fed v2 accepts full schemas -> there is no need to filter anything so you could just print out whole schema.