[Feature Request] Apollo Federation Support

Apollo Federation makes uses of some custom directives:

https://www.apollographql.com/docs/apollo-server/federation/federation-spec/

Version and Environment Details

Operation system: macOS

IDE name and version: IntelliJ IDEA Ultimate 2019.2

Plugin version: 2.2.0

Expected Behaviour

1. The following directives should not produce errors:

   directive @external on FIELD_DEFINITION
   directive @requires(fields: _FieldSet!) on FIELD_DEFINITION
   directive @provides(fields: _FieldSet!) on FIELD_DEFINITION
   directive @key(fields: _FieldSet!) on OBJECT | INTERFACE
   directive @extends on OBJECT | INTERFACE
   

   (These directives must NOT be in the GraphQL file itself)

2. An extend type TypeName should be allowed to exist without the base type, as the base type may be defined by another service

Actual Behaviour

1. Error: Unknown directive "XXX"
2. Error: The extension 'TypeName' type [@x:x] is missing its base underlying type

Steps to Reproduce / Link to Repo with Reproduction and Instructions

type InternalType @key(fields: "id") {
  id: ID!
  xyz: String!
  externalObject: ExternalType @requires(fields: "xyz") @provides(fields: "foo")
}

# In reality you need EITHER extend OR @extends
# depending on which server this schema is defined in
# (Apollo Server allows extend, graphql-java requires @extends)
extend type ExternalType @key(fields: "id") @extends {
  id: ID! @external
  foo: String! @external
  bar: String! @external
  baz: String!
}

[paulschwarz]

Looking at the examples of how to configure and extend the plugin (https://github.com/jimkyndemeyer/graphql-config-examples) perhaps a boilerplate example for Apollo Federation would help people get started.

[jimkyndemeyer]

Hi Nihal.

Thanks for using the plugin.

Like you mention, these directives are custom, and the plugin only ships with the directives that are described in the GraphQL spec. This is intentional, as new GraphQL frameworks appear all the time. For this reason you have to declare framework directives yourself, and ensure that they’re picked up as part of schema discovery. You can look at an example at https://github.com/jimkyndemeyer/graphql-config-examples/tree/master/extend-client-fields-and-directives which shows how to work with the @client Apollo directive.

Extending non-existing types violates the GraphQL Spec https://graphql.github.io/graphql-spec/June2018/#sec-Object-Extensions validation “The named type must already be defined and must be an Object type.” As such, graphql-java which this plugin is based on works correctly, so I’m not sure how we would go about adding support for this. Potentially the validation needs to be configurable as it makes sense to enforce it for other use cases.

I noted one interesting comment in your code example:

# (Apollo Server allows extend, graphql-java requires @extends)

If you declared your directives as expected, and used @extends I believe the plugin would work as is.

Best regards, Jim