Trying to better understand the federation transform.

[Davenporten]

So I have a graphql server, and I want to integrate it into my graphql-mesh instance. On this server I have a type

type User {
  username: ID!
}

which is used for a few different fields in other types.

I also have some typedefs and resolvers that live alongside my graphql-mesh configs that get incorporated into the unified schema. Among these I have a User type:

type User @key(fields: "username") {
 ...
 username: ID!
 ...
}

What I want to happen is when my graphql server is integrated to my mesh instance that federation can occur and when User is returned for query/mutation that's in the server it will be able to return the federated User, as in it has all those extra fields, etc. I've tried doing federation with the straight annotations

type User @key(fields: "username") @extends {
    username: ID! @external
}

But while this works if I'm using Apollo Federation tools (ApolloServer/ApolloGateway), graphql-mesh doesn't recognize @extends. So instead I want to add the annotations to the User type that's coming in from my server with something like

transforms:
  - federation:
      types:
        - name: Query
          config:
            extend: true
        - name: User
          config:
            extend: true
            keyFields:
              - username
            fields:
              - name: username
                config:
                  external: true

but this also doesn't work, I get

Type "User" already exists in the schema. It cannot also be defined in this type definition.

it seems that this is creating a new type User rather than modifying the User coming from my server. Is that how it's supposed to work? I thought it was going to change the type, but maybe I'm mistaken. If I am, is what I'm describing above even possible with graphql-mesh?

[ardatan]

Could you create an example with this scenario?

[renepardon]

I have the same problem with my implementation. I try to put graphql-mesh in front of a federated subgraph (service). But all I receive is:

❯ yarn run start
yarn run v1.22.10
$ mesh dev
🕸️ - Server: Serving GraphQL Mesh: http://0.0.0.0:4000 in 1 forks
🕸️: An error occured while writing the schema file: Unknown directive "@extends".
🕸️: An error occurred while building the mesh artifacts: Unknown directive "@extends".
🕸️ - Server: Generating Mesh schema...
🕸️: An error occured while writing the schema file: Unknown directive "@extends".
🕸️: An error occurred while building the mesh artifacts: Unknown directive "@extends".
🕸️ - Server: Unknown directive "@extends".

.meshrc.yaml contains:

sources:
  - name: TenantService
    handler:
      graphql:
        endpoint: http://localhost:8010/graphql
        operationHeaders:
          Authorization: "{context.headers['authorization']}"
  - name: UserService
    handler:
      graphql:
        endpoint: http://localhost:8020/graphql
        operationHeaders:
          Authorization: "{context.headers['authorization']}"

And the TenantService contains the following declaration to extend the User type by adding "tenant" to it:

type User @key(fields: "id") @extends {
    id: ID! @external
    tenant(filters: TenantOptions @spread): Tenant!
        @belongsTo(scopes: ["filters"])
        @can(ability: "tenant.show")
}

[ardatan]

Are you using Federation v2 alpha because Mesh doesn't support that currently.

[renepardon]

Just left my workplace. I will check on that on Monday but I use the latest nuwave/lighthouse php composer package, which provides federation.

[renepardon]

It’s based on https://www.apollographql.com/docs/federation/federation-spec

so not v2 alpha

[renepardon]

I also created a full ticket here: nuwave/lighthouse#2065

[renepardon]

I could solve the Query.node problem by removing the corresponding interface which was using @globalid. With Apollo Gateway I can get a working API Gateway now but GraphQL Mesh still complains about the unknown @extends directive:

An error occured while writing the schema file: Unknown directive "@extends"