Fix QueryScaffolder not using inheritance types

src/Scaffolding/Scaffolders/QueryScaffolder.php

@@ -85,7 +85,7 @@ public function getTypeName()
     protected function getType(Manager $manager)
     {
         // If an explicit type name has been provided, use it.
-        $typeName = $this->getTypeName();
+        $typeName = parent::getTypeName();
         if ($typeName && $manager->hasType($typeName)) {
             return $manager->getType($typeName);
         }

tests/Scaffolding/Scaffolders/QueryScaffolderTest.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace SilverStripe\GraphQL\Tests\Scaffolders\Scaffolding;
+
+use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
+use GraphQL\Type\Definition\UnionType;
+use SilverStripe\Dev\SapphireTest;
+use SilverStripe\GraphQL\Manager;
+use SilverStripe\GraphQL\Scaffolding\Scaffolders\ItemQueryScaffolder;
+use SilverStripe\GraphQL\Scaffolding\Scaffolders\SchemaScaffolder;
+use SilverStripe\GraphQL\Scaffolding\StaticSchema;
+use SilverStripe\GraphQL\Tests\Fake\FakePage;
+use SilverStripe\GraphQL\Tests\Fake\FakeRedirectorPage;
+
+class QueryScaffolderTest extends SapphireTest
+{
+    public function testInheritedTypes()
+    {
+        $scaffolder = new SchemaScaffolder();
+        $scaffolder
+            ->type(FakeRedirectorPage::class);
+        $scaffolder->addToManager($manager = new Manager());
+        $manager->addType(new ObjectType([
+            'name' => 'CustomTypeName',
+            'fields' => [
+                'Test' => Type::string(),
+            ]
+        ]));
+        $query = new ItemQueryScaffolder(null, 'CustomTypeName', null, FakePage::class);
+        $result = $query->scaffold($manager);
+        $type = $result['type'];
+        $this->assertInstanceOf(ObjectType::class, $type);
+        $this->assertEquals('CustomTypeName', $type->config['name']);
+
+        $query = new ItemQueryScaffolder(null, null, null, FakePage::class);
+        $result = $query->scaffold($manager);
+        $type = $result['type'];
+        $this->assertInstanceOf(UnionType::class, $type);
+        $this->assertEquals(
+            StaticSchema::inst()->inheritanceTypeNameForDataObject(FakePage::class),
+            $type->config['name']
+        );
+    }
+}