Is there a way to share fragments between schemas?...

# apollo-kotlin

[Charlie Tapping]

Is there a way to share fragments between schemas? Where I work we have several services which draw from a common schema which define types we expect from frontend facing services. For example Service A has its own schema, Service B has its own schema, but they both feature type Foo {}. Ideally I’d like to have one fragment for Foo defined and shared across both, is this possible?

[mbonnin]

Not really. Usually the best way to do this is server side using something like federation.

[mbonnin]

From the client side of things, there is no way to know 2 types are identical between two different schemas

[Charlie Tapping]

Hey @mbonnin, exactly yeah we’re using federation to share the common types on the backend. Client side I guess theres no way of expressing that federation through apollo? I’m thinking maybe I just make a common-fragments directory and symlink it into each dependant module 🤔

[mbonnin]

Federation is implementation detail as far as the client is concerned

[mbonnin]

The client should "just" see a big supergraph

[Charlie Tapping]

right okay, am I write in thinking apollo lets you create a service from multiple schema files? So in theory I could place my common schema in one module and my full service schema in another and they would be merged? If it allowed multiple schemas across modules?

[mbonnin]

schemaFiles is plural mainly in case you have client side schema extension

[mbonnin]

it cannot do federation composition

[mbonnin]

Federation composition belongs in the server

[mbonnin]

Your backend should ideally give you an "API schema" that is the result of all the merged schemas

[Charlie Tapping]

Ah it does, ultimately Service A and Services B schemas are just super sets of the common schema. I get that from a information perspective you don’t know how to decompose the aggregated schema, but theres no reason why you can’t supplement that on the client. It sounds like this is a fairly uncommon usecase anyway, I’ll figure out a more naive way of not repeating the fragments across modules. Thank you @mbonnin

[mbonnin]

Sure thing!