Adding aspects and annotations

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

@@ -142,10 +142,8 @@ trait GraphQL[-R] { self =>
       override val additionalDirectives: List[__Directive] = self.additionalDirectives
     }
 
-  /**
-   * A symbolic alias for `withWrapper`.
-   */
-  final def @@[R2 <: R](wrapper: Wrapper[R2]): GraphQL[R2] = withWrapper(wrapper)
+  final def @@[LowerR <: UpperR, UpperR <: R](aspect: GraphQLAspect[LowerR, UpperR]): GraphQL[UpperR] =
+    aspect(self)
 
   /**
    * Merges this GraphQL API with another GraphQL API.

core/src/main/scala/caliban/GraphQLAspect.scala

@@ -0,0 +1,13 @@
+package caliban
+
+trait GraphQLAspect[+LowerR, -UpperR] { self =>
+  def apply[R >: LowerR <: UpperR](gql: GraphQL[R]): GraphQL[R]
+
+  def @@[LowerR1 >: LowerR, UpperR1 <: UpperR](
+    other: GraphQLAspect[LowerR1, UpperR1]
+  ): GraphQLAspect[LowerR1, UpperR1] =
+    new GraphQLAspect[LowerR1, UpperR1] {
+      def apply[R >: LowerR1 <: UpperR1](gql: GraphQL[R]): GraphQL[R] =
+        other(self(gql))
+    }
+}

core/src/main/scala/caliban/wrappers/Wrapper.scala

@@ -9,6 +9,7 @@ import caliban.wrappers.Wrapper.CombinedWrapper
 import caliban.{ CalibanError, GraphQLRequest, GraphQLResponse, ResponseValue }
 import zio.{ UIO, ZIO }
 import zio.query.ZQuery
+import caliban.{ GraphQL, GraphQLAspect }
 
 /**
  * A `Wrapper[-R]` represents an extra layer of computation that can be applied on top of Caliban's query handling.
@@ -21,8 +22,11 @@ import zio.query.ZQuery
  *
  * It is also possible to combine wrappers using `|+|` and to build a wrapper effectfully with `EffectfulWrapper`.
  */
-sealed trait Wrapper[-R] { self =>
+sealed trait Wrapper[-R] extends GraphQLAspect[Nothing, R] { self =>
   def |+|[R1 <: R](that: Wrapper[R1]): Wrapper[R1] = CombinedWrapper(List(self, that))
+
+  def apply[R1 <: R](that: GraphQL[R1]): GraphQL[R1] =
+    that.withWrapper(self)
 }
 
 object Wrapper {

examples/src/main/scala/example/federation/FederatedApi.scala

@@ -4,7 +4,7 @@ import example.federation.CharacterService.CharacterService
 import example.federation.EpisodeService.EpisodeService
 
 import caliban.GraphQL.graphQL
-import caliban.federation.{EntityResolver, federate}
+import caliban.federation.{EntityResolver, federated}
 import caliban.federation.tracing.ApolloFederatedTracing
 import caliban.schema.Annotations.{GQLDeprecated, GQLDescription}
 import caliban.schema.{ArgBuilder, GenericSchema, Schema}
@@ -48,19 +48,9 @@ object FederatedApi {
     implicit val episodeArgs                                           = gen[EpisodeArgs]
     implicit val episodeArgBuilder: ArgBuilder[EpisodeArgs]            = ArgBuilder.gen[EpisodeArgs]
 
-    val api: GraphQL[Console with Clock with CharacterService] =
-      federate(
-        graphQL(
-          RootResolver(
-            Queries(
-              args => CharacterService.getCharacters(args.origin),
-              args => CharacterService.findCharacter(args.name)
-            ),
-            Mutations(args => CharacterService.deleteCharacter(args.name))
-          )
-        ) @@ standardWrappers,
-        EntityResolver.from[CharacterArgs](args => ZQuery.fromEffect(CharacterService.findCharacter(args.name))),
-        EntityResolver.from[EpisodeArgs](args =>
+    val withFederation = federated(        
+      EntityResolver.from[CharacterArgs](args => ZQuery.fromEffect(CharacterService.findCharacter(args.name))),
+      EntityResolver.from[EpisodeArgs](args =>
           ZQuery
             .fromEffect(CharacterService.getCharactersByEpisode(args.season, args.episode))
             .map(characters =>
@@ -72,8 +62,18 @@ object FederatedApi {
                 )
               )
             )
-        )
-      )
+        ))
+
+    val api: GraphQL[Console with Clock with CharacterService] =
+        graphQL(
+          RootResolver(
+            Queries(
+              args => CharacterService.getCharacters(args.origin),
+              args => CharacterService.findCharacter(args.name)
+            ),
+            Mutations(args => CharacterService.deleteCharacter(args.name))
+          )
+        ) @@ standardWrappers @@ withFederation
   }
 
   object Episodes extends GenericSchema[EpisodeService] {
@@ -89,19 +89,19 @@ object FederatedApi {
     implicit val episodeSchema      = gen[Episode]
 
     val api: GraphQL[Console with Clock with EpisodeService] =
-      federate(
         graphQL(
           RootResolver(
             Queries(
               args => EpisodeService.getEpisode(args.season, args.episode),
               args => EpisodeService.getEpisodes(args.season)
             )
           )
-        ) @@ standardWrappers,
+        ) @@ standardWrappers @@ federated(
         EntityResolver.from[EpisodeArgs](args =>
           ZQuery.fromEffect(EpisodeService.getEpisode(args.season, args.episode))
         )
-      )
+        )
+
   }
 
 }

federation/src/main/scala/caliban/federation/Federation.scala

@@ -6,7 +6,7 @@ import caliban.introspection.adt._
 import caliban.parsing.adt.Directive
 import caliban.schema.Step.QueryStep
 import caliban.schema._
-import caliban.{ CalibanError, GraphQL, InputValue, RootResolver }
+import caliban.{ CalibanError, GraphQL, GraphQLAspect, InputValue, RootResolver }
 import zio.query.ZQuery
 
 trait Federation {
@@ -48,6 +48,18 @@ trait Federation {
     GraphQL.graphQL(RootResolver(Query(_service = _Service(original.render))), federationDirectives) |+| original
   }
 
+  def federated[R](resolver: EntityResolver[R], others: EntityResolver[R]*): GraphQLAspect[Nothing, R] =
+    new GraphQLAspect[Nothing, R] {
+      def apply[R1 <: R](original: GraphQL[R1]): GraphQL[R1] =
+        federate(original, resolver, others: _*)
+    }
+
+  lazy val federated: GraphQLAspect[Nothing, Any] =
+    new GraphQLAspect[Nothing, Any] {
+      def apply[R1](original: GraphQL[R1]): GraphQL[R1] =
+        federate(original)
+    }
+
   /**
    * Accepts a GraphQL as well as entity resolvers in order to support more advanced federation use cases. This variant
    * will allow the gateway to query for entities by resolver.

federation/src/test/scala/caliban/federation/FederationSpec.scala

@@ -52,7 +52,7 @@ object FederationSpec extends DefaultRunnableSpec {
 
   override def spec = suite("FederationSpec")(
     testM("should resolve federated types") {
-      val interpreter = federate(graphQL(resolver), entityResolver).interpreter
+      val interpreter = (graphQL(resolver) @@ federated(entityResolver)).interpreter
 
       val query = gqldoc("""
             query test {
@@ -69,7 +69,7 @@ object FederationSpec extends DefaultRunnableSpec {
       )
     },
     testM("should not include _entities if not resolvers provided") {
-      val interpreter = federate(graphQL(resolver)).interpreter
+      val interpreter = (graphQL(resolver) @@ federated).interpreter
 
       val query = gqldoc("""
             query test {
@@ -93,7 +93,7 @@ object FederationSpec extends DefaultRunnableSpec {
       )
     },
     testM("should include orphan entities in sdl") {
-      val interpreter = federate(graphQL(resolver), orphanResolver).interpreter
+      val interpreter = (graphQL(resolver) @@ federated(orphanResolver)).interpreter
 
       val query = gqldoc("""{ _service { sdl } }""")
       assertM(interpreter.flatMap(_.execute(query)).map(d => d.data.toString))(
@@ -106,7 +106,7 @@ object FederationSpec extends DefaultRunnableSpec {
       )
     },
     testM("should include field metadata") {
-      val interpreter = federate(graphQL(resolver), functionEntityResolver).interpreter
+      val interpreter = (graphQL(resolver) @@ federated(functionEntityResolver)).interpreter
       val query       = gqldoc("""
            query Entities($withNicknames: Boolean = false) {
             _entities(representations: [{__typename: "Character", name: "Amos Burton"}]) {

vuepress/docs/docs/middleware.md

@@ -127,4 +127,31 @@ def withErrorCodeExtensions[R](
   case err: ParsingError =>
     err.copy(extensions = Some(ObjectValue(List(("errorCode", StringValue("PARSING_ERROR"))))))
 }
+```
+
+## Wrapping the GraphQL
+
+If you need to implement new functionality that involves not just changes to execution but also to the underlying
+schema you can use the higher-level `GraphQLAspect` which allows full control of the resulting `GraphQL` that it wraps.
+
+Here is such an example that is part of the `federation` package which makes a schema available to be used as a sub-graph in
+a federated graph:
+
+```scala
+  def federate[R](original: GraphQL[R]): GraphQL[R] = {
+    import Schema._
+
+    case class Query(
+      _service: _Service,
+      _fieldSet: FieldSet = FieldSet("")
+    )
+
+    GraphQL.graphQL(RootResolver(Query(_service = _Service(original.render))), federationDirectives) |+| original
+  }
+
+  lazy val federated: GraphQLAspect[Nothing, Any] = 
+    new GraphQLAspect[Nothing, Any] {
+      def apply[R1](original: GraphQL[R1]): GraphQL[R1] =
+        federate(original)
+    }
 ```