Enhance federated rendering

core/src/main/scala/caliban/GraphQL.scala

@@ -8,7 +8,7 @@ import caliban.introspection.adt._
 import caliban.parsing.adt.Definition.TypeSystemDefinition.SchemaDefinition
 import caliban.parsing.adt.{ Directive, Document, OperationType }
 import caliban.parsing.{ Parser, SourceMapper, VariablesCoercer }
-import caliban.rendering.DocumentRenderer
+import caliban.rendering.{ DocumentRenderer, Renderer }
 import caliban.schema._
 import caliban.transformers.Transformer
 import caliban.validation.{ SchemaValidator, Validator }
@@ -37,7 +37,14 @@ trait GraphQL[-R] { self =>
   /**
    * Returns a string that renders the API types into the GraphQL SDL.
    */
-  final def render: String = DocumentRenderer.render(toDocument)
+  final def render: String =
+    renderWith(DocumentRenderer)
+
+  /**
+   * Returns a string that renders types into the GraphQL SDL using the provided renderer.
+   */
+  final def renderWith(renderer: Renderer[Document]): String =
+    renderer.render(toDocument)
 
   /**
    * Converts the schema to a Document.

federation/src/main/scala/caliban/federation/v2x/FederationV2.scala

@@ -1,11 +1,26 @@
 package caliban.federation.v2x
 
+import caliban.GraphQL
 import caliban.federation.{ FederationDirectives, FederationSupport }
+import caliban.rendering.{ DocumentRenderer, Renderer }
 
 class FederationV2(extensions: List[Extension])
     extends FederationSupport(Nil, extensions.map(_.toDirective))
     with FederationDirectives
-    with FederationDirectivesV2
+    with FederationDirectivesV2 {
+
+  /**
+   * Constructs a renderer that can render a GraphQL schema with federation directives.
+   *
+   * This is useful if you need to render the schema to a string or file in CI or for debugging purposes.
+   *
+   * @note Make sure to use this renderer on the graph _before_ apply the federation aspect, otherwise it will include
+   *       the federation specific fields as well.
+   */
+  lazy val renderer: Renderer[GraphQL[_]] = DocumentRenderer.contramap[GraphQL[_]] {
+    _.withSchemaDirectives(extensions.map(_.toDirective)).toDocument
+  }
+}
 
 object FederationV2 {
 

federation/src/test/scala/caliban/federation/v2x/FederationV2Spec.scala

@@ -15,6 +15,8 @@ import zio.ZIO
 import zio.test.Assertion.hasSameElements
 import zio.test._
 
+import java.util.UUID
+
 object FederationV2Spec extends ZIOSpecDefault {
   override def spec =
     suite("FederationV2Spec")(
@@ -232,6 +234,33 @@ object FederationV2Spec extends ZIOSpecDefault {
           )
         }
 
+      },
+      test("renderer renders the schema including the extensions") {
+        import caliban.federation.v2_3._
+
+        @GQLKey("id")
+        @GQLShareable
+        case class Entity(
+          id: UUID
+        )
+
+        case class Query(
+          hello: String,
+          entity: Entity
+        )
+
+        val api = graphQL(
+          RootResolver(
+            Query(hello = "Hello World!", entity = Entity(UUID.randomUUID()))
+          )
+        )
+
+        assertTrue(
+          renderer.renderCompact(
+            api
+          ) == """schema@link(url:"https://specs.apollo.dev/federation/v2.3",import:["@key","@requires","@provides","@external","@shareable","@tag","@inaccessible","@override","@extends","@composeDirective","@interfaceObject"]){query:Query}type Entity@key(fields:"id")@shareable{id:ID!}type Query{hello:String! entity:Entity!}"""
+        )
+
       }
     )