feat: Support Federation v2 (#196)

* Add support for the @Shareable directive

* Fix rubocop offense

* Add support for the @inaccessible directive

* Add support for the @OverRide directive

* Refactor to appease rubocop

* Replace `Hash#except` with `Hash#delete_if`

Oops! I didn't realise `Hash#except` was only available from Ruby 3.0

* Update README to include v2.0 directives

* Fix incorrect handling of keyword args in field

* Import federation directives into subgraph to opt into federation 2 (hack!)

See: https://www.apollographql.com/docs/federation/federation-2/moving-to-federation-2/#opt-in-to-federation-2
This is a horrible hack. Need to figure out if there is a clean way of including this in the document and the printer output.

* Enable federation 2 via a `federation_2` class method on Schema

* Change `federation_2` to `federation version: 2`

This is more explicit and extendable in the future if we ever need any other federation options at the schema level

* Add a unit test for Schema.federation_version

* Update README with how to opt in to Federation v2

* Update federation version to support semantic versioning

* Add `federation__` namespace prefix to all directives when using federation version >= 2.0

* Refactor the `merge_directives` method

This approach feel a little easier to understand

* Fix grammar issues in test names

Author: col

README.md

@@ -61,6 +61,15 @@ class MySchema < GraphQL::Schema
 end
 ```
 
+**Optional:** To opt in to Federation v2, specify the version in your schema:
+
+```ruby
+class MySchema < GraphQL::Schema
+  include ApolloFederation::Schema
+  federation version: '2.0'
+end
+```
+
 ## Example
 
 The [`example`](./example/) folder contains a Ruby implementation of Apollo's [`federation-demo`](https://github.com/apollographql/federation-demo). To run it locally, install the Ruby dependencies:
@@ -160,6 +169,59 @@ end
 ```
 See [field set syntax](#field-set-syntax) for more details on the format of the `fields` option.
 
+### The `@shareable` directive (Apollo Federation v2)
+
+[Apollo documentation](https://www.apollographql.com/docs/federation/federated-types/federated-directives/#shareable)
+
+Call `shareable` within your class definition:
+
+```ruby
+class User < BaseObject
+  shareable
+end
+```
+
+Pass the `shareable: true` option to your field definition:
+
+```ruby
+class User < BaseObject
+  field :id, ID, null: false, shareable: true
+end
+```
+
+### The `@inaccessible` directive (Apollo Federation v2)
+
+[Apollo documentation](https://www.apollographql.com/docs/federation/federated-types/federated-directives/#inaccessible)
+
+Call `inaccessible` within your class definition:
+
+```ruby
+class User < BaseObject
+  inaccessible
+end
+```
+
+Pass the `inaccessible: true` option to your field definition:
+
+```ruby
+class User < BaseObject
+  field :id, ID, null: false, inaccessible: true
+end
+```
+
+### The `@override` directive (Apollo Federation v2)
+
+[Apollo documentation](https://www.apollographql.com/docs/federation/federated-types/federated-directives/#override)
+
+Pass the `override:` option to your field definition:
+
+```ruby
+class Product < BaseObject
+  field :id, ID, null: false
+  field :inStock, Boolean, null: false, override: { from: 'Products' }
+end
+```
+
 ### Field set syntax
 
 Field sets can be either strings encoded with the Apollo Field Set [syntax]((https://www.apollographql.com/docs/apollo-server/federation/federation-spec/#scalar-_fieldset)) or arrays, hashes and snake case symbols that follow the graphql-ruby conventions:

lib/apollo-federation/federated_document_from_schema_definition.rb

@@ -55,14 +55,14 @@ def query_type?(type)
 
     def merge_directives(node, type)
       if type.is_a?(ApolloFederation::HasDirectives)
-        directives = type.federation_directives
+        directives = type.federation_directives || []
       else
         directives = []
       end
 
-      (directives || []).each do |directive|
+      directives.each do |directive|
         node = node.merge_directive(
-          name: directive[:name],
+          name: schema.federation_2? ? "federation__#{directive[:name]}" : directive[:name],
           arguments: build_arguments_node(directive[:arguments]),
         )
       end

lib/apollo-federation/field.rb

@@ -7,10 +7,29 @@ module ApolloFederation
   module Field
     include HasDirectives
 
-    def initialize(*args, external: false, requires: nil, provides: nil, **kwargs, &block)
+    VERSION_1_DIRECTIVES = %i[external requires provides].freeze
+    VERSION_2_DIRECTIVES = %i[shareable inaccessible override].freeze
+
+    def initialize(*args, **kwargs, &block)
+      add_v1_directives(**kwargs)
+      add_v2_directives(**kwargs)
+
+      # Remove the custom kwargs
+      kwargs = kwargs.delete_if do |k, _|
+        VERSION_1_DIRECTIVES.include?(k) || VERSION_2_DIRECTIVES.include?(k)
+      end
+
+      # Pass on the default args:
+      super(*args, **kwargs, &block)
+    end
+
+    private
+
+    def add_v1_directives(external: nil, requires: nil, provides: nil, **_kwargs)
       if external
         add_directive(name: 'external')
       end
+
       if requires
         add_directive(
           name: 'requires',
@@ -23,6 +42,7 @@ def initialize(*args, external: false, requires: nil, provides: nil, **kwargs, &
           ],
         )
       end
+
       if provides
         add_directive(
           name: 'provides',
@@ -36,8 +56,29 @@ def initialize(*args, external: false, requires: nil, provides: nil, **kwargs, &
         )
       end
 
-      # Pass on the default args:
-      super(*args, **kwargs, &block)
+      nil
+    end
+
+    def add_v2_directives(shareable: nil, inaccessible: nil, override: nil, **_kwargs)
+      if shareable
+        add_directive(name: 'shareable')
+      end
+
+      if inaccessible
+        add_directive(name: 'inaccessible')
+      end
+
+      if override
+        add_directive(
+          name: 'override',
+          arguments: [
+            name: 'from',
+            values: override[:from],
+          ],
+        )
+      end
+
+      nil
     end
   end
 end

lib/apollo-federation/interface.rb

@@ -18,6 +18,10 @@ def extend_type
         add_directive(name: 'extends')
       end
 
+      def inaccessible
+        add_directive(name: 'inaccessible')
+      end
+
       def key(fields:, camelize: true)
         add_directive(
           name: 'key',

lib/apollo-federation/object.rb

@@ -16,6 +16,14 @@ def extend_type
         add_directive(name: 'extends')
       end
 
+      def shareable
+        add_directive(name: 'shareable')
+      end
+
+      def inaccessible
+        add_directive(name: 'inaccessible')
+      end
+
       def key(fields:, camelize: true)
         add_directive(
           name: 'key',

lib/apollo-federation/schema.rb

@@ -12,9 +12,30 @@ def self.included(klass)
     end
 
     module CommonMethods
+      FEDERATION_2_PREFIX = <<~SCHEMA
+        extend schema
+          @link(url: "https://specs.apollo.dev/federation/v2.0")
+
+      SCHEMA
+
+      def federation(version: '1.0')
+        @federation_version = version
+      end
+
+      def federation_version
+        @federation_version || '1.0'
+      end
+
+      def federation_2?
+        Gem::Version.new(federation_version.to_s) >= Gem::Version.new('2.0.0')
+      end
+
       def federation_sdl(context: nil)
         document_from_schema = FederatedDocumentFromSchemaDefinition.new(self, context: context)
-        GraphQL::Language::Printer.new.print(document_from_schema.document)
+
+        output = GraphQL::Language::Printer.new.print(document_from_schema.document)
+        output.prepend(FEDERATION_2_PREFIX) if federation_2?
+        output
       end
 
       def query(new_query_object = nil)

spec/apollo-federation/schema_spec.rb

@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'graphql'
+require 'apollo-federation/schema'
+
+RSpec.describe ApolloFederation::Schema do
+  describe '.federation_version' do
+    it 'returns 1.0 by default' do
+      schema = Class.new(GraphQL::Schema) do
+        include ApolloFederation::Schema
+      end
+
+      expect(schema.federation_version).to eq('1.0')
+    end
+
+    it 'returns the specified version when set' do
+      schema = Class.new(GraphQL::Schema) do
+        include ApolloFederation::Schema
+        federation version: '2.0'
+      end
+
+      expect(schema.federation_version).to eq('2.0')
+    end
+  end
+
+  describe '.federation_2?' do
+    it 'returns false when version is an integer less than 2.0' do
+      schema = Class.new(GraphQL::Schema) do
+        include ApolloFederation::Schema
+        federation version: 1
+      end
+
+      expect(schema.federation_2?).to be(false)
+    end
+
+    it 'returns false when version is less than 2.0' do
+      schema = Class.new(GraphQL::Schema) do
+        include ApolloFederation::Schema
+        federation version: '1.5'
+      end
+
+      expect(schema.federation_2?).to be(false)
+    end
+
+    it 'returns true when the version is an integer equal to 2' do
+      schema = Class.new(GraphQL::Schema) do
+        include ApolloFederation::Schema
+        federation version: 2
+      end
+
+      expect(schema.federation_2?).to be(true)
+    end
+
+    it 'returns true when the version is a float equal to 2.0' do
+      schema = Class.new(GraphQL::Schema) do
+        include ApolloFederation::Schema
+        federation version: 2.0
+      end
+
+      expect(schema.federation_2?).to be(true)
+    end
+
+    it 'returns true when the version is a string greater than 2.0' do
+      schema = Class.new(GraphQL::Schema) do
+        include ApolloFederation::Schema
+        federation version: '2.0.1'
+      end
+
+      expect(schema.federation_2?).to be(true)
+    end
+  end
+end