API Don't create "peripheral" operations by default

README.md

@@ -1501,27 +1501,27 @@ SilverStripe\GraphQL\Manager:
             ##...
           SilverStripe\CMS\Model\RedirectorPage:
             fields: [ID, ExternalURL, Content]
+          Page:
+            fields: [MyCustomField]
             operations:
               read: true
               create: true
-          Page:
-            fields: [MyCustomField]
 ```
 
 **... Or with code**:
 ```php
 $scaffolder
     ->type('SilverStripe\CMS\Model\RedirectorPage')
         ->addFields(['ID', 'ExternalURL', 'Content'])
+        ->end()
+    ->type('Page')
+        ->addFields(['MyCustomField'])
         ->operation(SchemaScaffolder::READ)
             ->setName('readRedirectors')
             ->end()
         ->operation(SchemaScaffolder::CREATE)
             ->setName('createRedirector')
             ->end()
-        ->end()
-    ->type('Page')
-        ->addFields(['MyCustomField'])
         ->end();
 ```
 
@@ -1554,44 +1554,84 @@ type SiteTreeWithDescendants {
   SiteTree | Page | RedirectorPage
 }
 
-input RedirectorPageCreateInputType {
-  ExternalURL: String
-  RedirectionType: String
-  MyCustomField: String
-  Content: String
-  # all other fields from RedirectorPage, Page and SiteTree
-}
-
 input PageCreateInputType {
   MyCustomField: String
   Content: String
   # all other fields from Page and SiteTree
 }
 
-input SiteTreeCreateInputType {
-  # all fields from SiteTree
+query readPages {
+  PageWithDescendants
 }
 
-query readRedirectors {
-  RedirectorPage
+mutation createPage {
+  PageCreateInputType
 }
+```
 
-query readPages {
-  PageWithDescendants
+By default, types are created for the full inheritance tree.
+In certain situations, you may also want to create operations for all these ancestors and descendants.
+For example, `createPage` only allows you to create an object of type `Page`.
+In order to define a `createRedirectorPage` equivalent to create an object of type `RedirectorPage`,
+you need to opt in via the `cloneable` configuration setting: 
+
+
+**Via YAML**:
+```yaml
+SilverStripe\GraphQL\Manager:
+  schemas:
+    default:
+      scaffolding:
+        types:
+          MyProject\Post:
+            ##...
+          SilverStripe\CMS\Model\RedirectorPage:
+            fields: [ID, ExternalURL, Content]
+          Page:
+            fields: [MyCustomField]
+            operations:
+              read: true
+              create:
+                cloneable: true
+```
+
+**... Or with code**:
+```php
+$scaffolder
+    ->type('SilverStripe\CMS\Model\RedirectorPage')
+        ->addFields(['ID', 'ExternalURL', 'Content'])
+        ->end()
+    ->type('Page')
+        ->addFields(['MyCustomField'])
+        ->operation(SchemaScaffolder::READ)
+            ->setName('readRedirectors')
+            ->setCloneable(true)
+            ->end()
+        ->operation(SchemaScaffolder::CREATE)
+            ->setName('createRedirector')
+            ->end()
+        ->end();
+```
+
+This will add the following fields to your schema:
+
+```graphql
+input RedirectorPageCreateInputType {
+  ExternalURL: String
+  RedirectionType: String
+  MyCustomField: String
+  Content: String
+  # all other fields from RedirectorPage, Page and SiteTree
 }
 
-query readSiteTrees {
-  SiteTreeWithDescendants
+input SiteTreeCreateInputType {
+  # all fields from SiteTree
 }
 
 mutation createRedirector {
   RedirectorPageCreateInputType
 }
 
-mutation createPage {
-  PageCreateInputType
-}
-
 mutation createSiteTree {
   SiteTreeCreateInputType
 }
@@ -1604,15 +1644,16 @@ when `RedirectorPage` is also exposed), a union is returned, and you will need t
 with the `...on {type}` GraphQL syntax.
 
 ```graphql
-query readSiteTrees {
-  readSiteTrees {
+query readPages {
+  readPages {
     edges {
       node {
         __typename
         ...on Page {
           ID
         }
         ...on RedirectorPage {
+          ID
           RedirectionType
         }
       }

src/Scaffolding/Scaffolders/DataObjectScaffolder.php

@@ -412,6 +412,10 @@ public function cloneTo(DataObjectScaffolder $target)
             }
         }
         foreach ($this->getOperations() as $op) {
+            if (!$op->getCloneable()) {
+                continue;
+            }
+
             $identifier = OperationScaffolder::getIdentifier($op);
             $target->operation($identifier);
         }

src/Scaffolding/Scaffolders/OperationScaffolder.php

@@ -48,6 +48,31 @@ abstract class OperationScaffolder implements ConfigurationApplier
      */
     protected $args = [];
 
+    /**
+     * @var bool Indicates that this operation should be
+     * included in clones to other types.
+     */
+    protected $cloneable = false;
+
+    /**
+     * @return bool
+     */
+    public function getCloneable()
+    {
+        return $this->cloneable;
+    }
+
+    /**
+     * @param bool $cloneable
+     * @return $this
+     */
+    public function setCloneable($cloneable)
+    {
+        $this->cloneable = $cloneable;
+
+        return $this;
+    }
+
     /**
      * @param string $name
      * @return  string|null
@@ -399,13 +424,19 @@ public function applyConfig(array $config)
                 }
             }
         }
+
         if (isset($config['resolver'])) {
             $this->setResolver($config['resolver']);
         }
+
         if (isset($config['name'])) {
             $this->setName($config['name']);
         }
 
+        if (isset($config['cloneable'])) {
+            $this->setCloneable((bool)$config['cloneable']);
+        }
+
         return $this;
     }
 

src/Scaffolding/Scaffolders/SchemaScaffolder.php

@@ -60,6 +60,7 @@ class SchemaScaffolder implements ManagerMutatorInterface
      */
     public static function createFromConfig($config)
     {
+        /** @var self $scaffolder */
         $scaffolder = Injector::inst()->get(self::class);
         if (isset($config['types'])) {
             if (!ArrayLib::is_associative($config['types'])) {
@@ -284,6 +285,7 @@ public function getMutations()
     public function addToManager(Manager $manager)
     {
         $this->registerFixedTypes($manager);
+
         $this->registerPeripheralTypes($manager);
 
         $this->extend('onBeforeAddToManager', $manager);

tests/Scaffolding/Scaffolders/DataObjectScaffolderTest.php

@@ -480,7 +480,22 @@ public function testCloneTo()
 
         $this->assertContains('Title', $target->getFields()->column('Name'));
         $this->assertNotContains('RedirectionType', $target->getFields()->column('Name'));
-        $this->assertCount(2, $target->getOperations());
+        $this->assertCount(0, $target->getOperations(), 'Does not clone operations by default');
+    }
+
+    public function testCloneToWithCloneable()
+    {
+        $scaffolder = new DataObjectScaffolder(FakeSiteTree::class);
+        $scaffolder->addFields(['Title', 'ID']);
+        $scaffolder->operation(SchemaScaffolder::READ);
+        $scaffolder->operation(SchemaScaffolder::UPDATE)->setCloneable(true);
+
+        $target = new DataObjectScaffolder(FakeRedirectorPage::class);
+        $target = $scaffolder->cloneTo($target);
+        $this->assertEquals(
+            ['updateSilverStripeFakeRedirectorPage'],
+            $target->getOperations()->column('getName')
+        );
     }
 
     /**

tests/Scaffolding/Scaffolders/SchemaScaffolderTest.php

@@ -86,8 +86,10 @@ public function testSchemaScaffolderAddToManager()
             ->type(FakeRedirectorPage::class)
                 ->addFields(['Created', 'TestPageField', 'RedirectionType'])
                 ->operation(SchemaScaffolder::CREATE)
+                    ->setCloneable(true)
                     ->end()
                 ->operation(SchemaScaffolder::READ)
+                    ->setCloneable(true)
                     ->end()
                 ->end()
             ->type(DataObjectFake::class)
@@ -284,9 +286,11 @@ public function testUnionInheritanceForTypes()
             ->addFields(['Title', 'RedirectionType'])
             ->operation(SchemaScaffolder::READ)
                 ->setName('READ')
+                ->setCloneable(true)
             ->end()
             ->operation(SchemaScaffolder::DELETE)
                 ->setName('DELETE')
+                ->setCloneable(true)
             ->end()
             ->end();
         $scaffolder->addToManager($manager = new Manager());