fix(utils/mapSchema): do not map builtin scalars (#5294)

* add failing test

* Fix

---------

Co-authored-by: Arda TANRIKULU <[email protected]>

Author: n1ru4l

.changeset/social-pots-grab.md

@@ -0,0 +1,5 @@
+---
+'@graphql-tools/utils': patch
+---
+
+Do not map builtin scalars

packages/utils/src/mapSchema.ts

@@ -14,6 +14,7 @@ import {
   GraphQLNonNull,
   GraphQLObjectType,
   GraphQLObjectTypeConfig,
+  GraphQLScalarType,
   GraphQLSchema,
   GraphQLType,
   InputValueDefinitionNode,
@@ -28,6 +29,7 @@ import {
   isScalarType,
   isUnionType,
   Kind,
+  specifiedScalarTypes,
 } from 'graphql';
 import { getObjectTypeFromTypeMap } from './getObjectTypeFromTypeMap.js';
 import {
@@ -109,7 +111,10 @@ function mapTypes(
     if (!typeName.startsWith('__')) {
       const originalType = originalTypeMap[typeName];
 
-      if (originalType == null || !testFn(originalType)) {
+      if (
+        originalType == null ||
+        (!testFn(originalType) && !specifiedScalarTypes.includes(originalType as GraphQLScalarType))
+      ) {
         newTypeMap[typeName] = originalType;
         continue;
       }

packages/utils/tests/mapSchema.test.ts

@@ -93,6 +93,23 @@ describe('mapSchema', () => {
     expect(newSchema.getQueryType()?.name).toBe('RootQuery');
   });
 
+  test('map scalar type', () => {
+    const schema = buildSchema(/* GraphQL */ `
+      type Query {
+        _: Boolean
+      }
+    `);
+
+    mapSchema(schema, {
+      [MapperKind.SCALAR_TYPE](type) {
+        const config = type.toConfig();
+        return new GraphQLScalarType({
+          ...config,
+        });
+      },
+    });
+  });
+
   const typeDefs = /* GraphQL */ `
     directive @schemaDirective(role: String) on SCHEMA
     directive @schemaExtensionDirective(role: String) on SCHEMA