Modify federation to be possible with edn schema as well

deps.edn

@@ -51,4 +51,4 @@
 
  :codox/config
  {:description "Clojure-native implementation of GraphQL"
-  :source-uri "https://github.com/walmartlabs/lacinia/blob/master/{filepath}#L{line}"}}
+  :source-uri "https://github.com/walmartlabs/lacinia/blob/master/{filepath}#L{line}"}}

dev-resources/edn-federation.edn

@@ -0,0 +1,81 @@
+{:roots
+ {:query :Query
+  :mutation :Mutation
+  :subscription :Subscription}
+ :objects
+ {:_Service
+  {:fields
+   {:sdl
+    {:type (non-null String)}}}
+  :User
+  {:fields
+   {:id
+    {:type (non-null Int)}
+    :name
+    {:type (non-null String)}}
+   :directives [{:directive-type :key :directive-args {:fields "id"}}]}
+  :Query
+  {:fields
+   {:user_by_id
+    {:type :User :args
+     {:id
+      {:type (non-null Int)}}}}}
+  :Account
+  {:fields
+   {:acct_number
+    {:type (non-null String)} :name
+    {:type (non-null String)}}
+   :directives [{:directive-type :key :directive-args {:fields "acct_number"}}]}
+  :Product
+  {:fields
+   {:upc
+    {:type (non-null String) :directives [{:directive-type :external}]} :reviewed_by
+    {:type :User}}
+   :directives [{:directive-type :key :directive-args {:fields "upc"}}
+                {:directive-type :extends}]}}
+ :scalars
+ {:_Any
+  {:parse :_Any/parser,
+   :serialize :_Any/serializer},
+  :_FieldSet
+  {:parse :_FieldSet/parser,
+   :serialize :_FieldSet/serializer}
+  :link__Import
+  {:parse :link__Import/parser,
+   :serialize :link__Import/serializer}}
+
+ :enums
+ {:link__Purpose
+  {:values [{:enum-value :SECURITY} {:enum-value :EXECUTION}]}}
+
+ :directive-defs
+ {:external
+  {:locations #{:field-definition}}
+  :requires
+  {:locations #{:field-definition}
+   :args {:fields {:type (non-null _FieldSet)}}}
+  :provides
+  {:locations #{:field-definition}
+   :args {:fields {:type (non-null _FieldSet)}}}
+  :key
+  {:locations #{:object :interface}
+   :args {:fields {:type (non-null _FieldSet)}
+          :resolvable {:type Boolean :default-value true}}}
+  :link
+  {:locations #{:schema},
+   :args {:url {:type String}, :as {:type String}, :for {:type :link__Purpose}, :import {:type (list :link__Import)}}}
+  :shareable {:locations #{:field-definition :object}},
+  :inaccessible
+  {:locations
+   #{:enum
+     :input-field-definition
+     :interface
+     :input-object
+     :enum-value
+     :scalar
+     :argument-definition
+     :union
+     :field-definition
+     :object}},
+  :override {:locations #{:field-definition}, :args {:from {:type (non-null String)}}},
+  :extends {:locations #{:interface :object}}}}

dev-resources/edn-federation.sdl

@@ -0,0 +1,43 @@
+schema {
+  query: Query
+  mutation: Mutation
+  subscription: Subscription
+}
+
+directive @extends on INTERFACE | OBJECT
+directive @key(fields: _FieldSet!, resolvable: Boolean = true) on INTERFACE | OBJECT
+directive @external on FIELD_DEFINITION
+directive @shareable on FIELD_DEFINITION | OBJECT
+directive @requires(fields: _FieldSet!) on FIELD_DEFINITION
+directive @link(url: String, as: String, for: link__Purpose, import: [link__Import]) on SCHEMA
+directive @provides(fields: _FieldSet!) on FIELD_DEFINITION
+directive @override(from: String!) on FIELD_DEFINITION
+directive @inaccessible on ENUM | INPUT_FIELD_DEFINITION | INTERFACE | INPUT_OBJECT | ENUM_VALUE | SCALAR | ARGUMENT_DEFINITION | UNION | FIELD_DEFINITION | OBJECT
+
+scalar _Any
+scalar _FieldSet
+scalar link__Import
+
+enum link__Purpose{
+  SECURITY
+  EXECUTION
+}
+
+type _Service{
+  sdl: String!
+}
+type User @key(fields: "id") {
+  id: Int!
+  name: String!
+}
+type Query{
+  user_by_id(id: Int!): User
+}
+type Account @key(fields: "acct_number") {
+  acct_number: String!
+  name: String!
+}
+type Product @key(fields: "upc") @extends {
+  upc: String!
+  reviewed_by: User
+}

docs/federation/index.rst

@@ -14,11 +14,6 @@ service-spanning queries apart and build an overall query plan.
 Lacinia has been extended, starting in 0.38.0, to support acting as an implementing service; there is no plan
 at this time to act as a gateway.
 
-.. warning::
-
-    At this time, only a schema defined with the :doc:`Schema Definition Language </schema/parsing>`, can be extended to act as
-    a service implementation.
-
 Essentially, federation allows a set of services to each provide their own types, queries, and mutations, and organizes things so that
 each service can provide additional fields to the types provided by the other services.