[Scala 3] Fix derivation of case objects / parameterless case classes that contain @GQLField methods

core/src/main/scala-3/caliban/schema/SchemaDerivation.scala

@@ -106,20 +106,20 @@ trait CommonSchemaDerivation {
 
       case m: Mirror.ProductOf[A] =>
         inline erasedValue[m.MirroredElemLabels] match {
-          case _: EmptyTuple                              =>
+          case _: EmptyTuple if !Macros.hasFieldsFromMethods[A] =>
             new EnumValueSchema[R, A](
               MagnoliaMacro.typeInfo[A],
               // Workaround until we figure out why the macro uses the parent's annotations when the leaf is a Scala 3 enum
               inline if (!MagnoliaMacro.isEnum[A]) MagnoliaMacro.anns[A] else Nil,
               config.enableSemanticNonNull
             )
-          case _ if Macros.hasAnnotation[A, GQLValueType] =>
+          case _ if Macros.hasAnnotation[A, GQLValueType]       =>
             new ValueTypeSchema[R, A](
               valueTypeSchema[R, m.MirroredElemLabels, m.MirroredElemTypes],
               MagnoliaMacro.typeInfo[A],
               MagnoliaMacro.anns[A]
             )
-          case _                                          =>
+          case _                                                =>
             new ObjectSchema[R, A](
               recurseProduct[R, A, m.MirroredElemLabels, m.MirroredElemTypes]()(),
               Macros.fieldsFromMethods[R, A],

core/src/main/scala-3/caliban/schema/macros/Macros.scala

@@ -13,6 +13,9 @@ object Macros {
   inline def implicitExists[T]: Boolean     = ${ implicitExistsImpl[T] }
   inline def hasAnnotation[T, Ann]: Boolean = ${ hasAnnotationImpl[T, Ann] }
 
+  transparent inline def hasFieldsFromMethods[T]: Boolean =
+    ${ hasFieldsFromMethodsImpl[T] }
+
   transparent inline def fieldsFromMethods[R, T]: List[(String, List[Any], Schema[R, ?])] =
     ${ fieldsFromMethodsImpl[R, T] }
 
@@ -48,6 +51,15 @@ object Macros {
     Expr(TypeRepr.of[P].typeSymbol.flags.is(Flags.Enum) && TypeRepr.of[T].typeSymbol.flags.is(Flags.Enum))
   }
 
+  private def hasFieldsFromMethodsImpl[T: Type](using q: Quotes): Expr[Boolean] = {
+    import q.reflect.*
+    val targetSym = TypeTree.of[T].symbol
+    val annType   = TypeRepr.of[GQLField]
+    val annSym    = annType.typeSymbol
+
+    Expr(targetSym.declaredMethods.exists(_.getAnnotation(annSym).isDefined))
+  }
+
   private def fieldsFromMethodsImpl[R: Type, T: Type](using
     q: Quotes
   ): Expr[List[(String, List[Any], Schema[R, ?])]] = {

core/src/test/scala-3/caliban/schema/Scala3DerivesSpec.scala

@@ -292,27 +292,27 @@ object Scala3DerivesSpec extends ZIOSpecDefault {
 
         val expectedSchema =
           """schema {
-  query: Query
-}
-
-"Union type Payload"
-union Payload2 @mydirective(arg: "value") = Foo | Bar | Baz
-
-type Bar {
-  foo: Int!
-}
-
-type Baz {
-  bar: Int!
-}
-
-type Foo {
-  value: String!
-}
-
-type Query {
-  testQuery(isFoo: Boolean!): Payload2!
-}""".stripMargin
+            |  query: Query
+            |}
+            |
+            |"Union type Payload"
+            |union Payload2 @mydirective(arg: "value") = Foo | Bar | Baz
+            |
+            |type Bar {
+            |  foo: Int!
+            |}
+            |
+            |type Baz {
+            |  bar: Int!
+            |}
+            |
+            |type Foo {
+            |  value: String!
+            |}
+            |
+            |type Query {
+            |  testQuery(isFoo: Boolean!): Payload2!
+            |}""".stripMargin
         val interpreter    = gql.interpreterUnsafe
 
         for {
@@ -325,6 +325,44 @@ type Query {
           data2 == """{"testQuery":{"foo":1}}""",
           gql.render == expectedSchema
         )
+      },
+      test("case object with @GQLField methods") {
+        case object Foo derives Schema.SemiAuto {
+          @GQLField def fooValue: Option[String] = None
+          @GQLField def barValue: Int            = 42
+        }
+        val rendered = graphQL(RootResolver(Foo)).render
+
+        val expected =
+          """schema {
+            |  query: Foo
+            |}
+            |
+            |type Foo {
+            |  fooValue: String
+            |  barValue: Int!
+            |}""".stripMargin
+
+        assertTrue(rendered == expected)
+      },
+      test("parameterless case class with @GQLField methods") {
+        case class Foo() derives Schema.SemiAuto {
+          @GQLField def fooValue: Option[String] = None
+          @GQLField def barValue: Int            = 42
+        }
+        val rendered = graphQL(RootResolver(Foo())).render
+
+        val expected =
+          """schema {
+            |  query: Foo
+            |}
+            |
+            |type Foo {
+            |  fooValue: String
+            |  barValue: Int!
+            |}""".stripMargin
+
+        assertTrue(rendered == expected)
       }
     )
   }