fix: Correctly pipes up scalar serialization

Package.swift

@@ -26,7 +26,7 @@ let package = Package(
         ),
     ],
     dependencies: [
-        .package(url: "https://github.com/GraphQLSwift/GraphQL.git", from: "4.1.0"),
+        .package(url: "https://github.com/GraphQLSwift/GraphQL.git", from: "4.3.0"),
         .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.3.0"),
         .package(url: "https://github.com/swiftlang/swift-syntax.git", "600.0.1"..<"603.0.0"),
         .package(url: "https://github.com/jpsim/Yams.git", "4.0.0"..<"7.0.0"),
@@ -61,7 +61,7 @@ let package = Package(
         .testTarget(
             name: "GraphQLGeneratorCoreTests",
             dependencies: [
-                "GraphQLGeneratorCore"
+                "GraphQLGeneratorCore",
             ]
         ),
         .testTarget(

Sources/GraphQLGeneratorCore/Generator/BuildGraphQLSchemaGenerator.swift

@@ -28,6 +28,22 @@ package struct BuildGraphQLSchemaGenerator {
             !$0.name.hasPrefix("__")
         }
 
+        // Apply serialize and parse methods for scalar types
+        let scalarTypes = types.compactMap {
+            $0 as? GraphQLScalarType
+        }
+        for scalar in scalarTypes {
+            // Avoid default scalars
+            guard scalar.astNode != nil else {
+                continue
+            }
+            output += """
+
+
+                \(generateScalarType(for: scalar).indent(1))
+                """
+        }
+
         // Generate type definitions for all object types
         let interfaceTypes = types.compactMap {
             $0 as? GraphQLInterfaceType
@@ -94,6 +110,20 @@ package struct BuildGraphQLSchemaGenerator {
         return output
     }
 
+    func generateScalarType(for type: GraphQLScalarType) -> String {
+        let swiftType = mapScalarType(type, nameGenerator: nameGenerator)
+        return """
+
+
+            if let scalar = schema.typeMap["\(type.name)"] as? GraphQLScalarType {
+                scalar.serialize = { try \(swiftType).serialize(any: $0) }
+                scalar.parseValue = { try \(swiftType).parseValue(map: $0) }
+                scalar.parseLiteral = { try \(swiftType).parseLiteral(value: $0) }
+            }
+
+            """
+    }
+
     func generateInterfaceType(for type: GraphQLInterfaceType) throws -> String {
         let typeName = nameGenerator.swiftMemberName(for: type.name)
         let variableName = "\(typeName)Fields"

Sources/GraphQLGeneratorCore/Utilities/swiftTypeName.swift

@@ -105,11 +105,10 @@ func swiftTypeDeclaration(
     throw GeneratorError.unsupportedType("Unknown type: \(type)")
 }
 
-/// Map GraphQL leaf types to Swift types.
+/// Map GraphQL scalar types to Swift types.
 ///
 /// - Parameters:
 ///   - graphQLType: The GraphQL Type to generate a reference to
-///   - includeNamespace: Whether to include the `GraphQLGenerated` type namespace in the result
 ///   - nameGenerator: The name generator
 func mapScalarType(_ type: GraphQLScalarType, nameGenerator: SafeNameGenerator) -> String {
     switch type.name {

Tests/GraphQLGeneratorCoreTests/SchemaGeneratorTests.swift

@@ -87,6 +87,25 @@ struct SchemaGeneratorTests {
         )
     }
 
+    @Test func generateScalarType() throws {
+        let scalar = try GraphQLScalarType(name: "EmailAddress")
+
+        let result = generator.generateScalarType(for: scalar)
+
+        let expected = """
+
+
+            if let scalar = schema.typeMap["EmailAddress"] as? GraphQLScalarType {
+                scalar.serialize = { try GraphQLScalars.EmailAddress.serialize(any: $0) }
+                scalar.parseValue = { try GraphQLScalars.EmailAddress.parseValue(map: $0) }
+                scalar.parseLiteral = { try GraphQLScalars.EmailAddress.parseLiteral(value: $0) }
+            }
+
+            """
+
+        #expect(result == expected)
+    }
+
     @Test func generateInterfaceType() throws {
         let interfaceType = try GraphQLInterfaceType(
             name: "Node",