From 9c48b9398323450a3cae83b8ed33e32d7ef0925f Mon Sep 17 00:00:00 2001
From: Damian Mooyman <damian@silverstripe.com>
Date: Mon, 5 Sep 2016 18:46:00 +1200
Subject: [PATCH] BUG Ensure changes in class write to an instance of the new
 class, not the old one Fixes #1210 Requires
 https://github.com/silverstripe/silverstripe-framework/pull/5950

---
 code/Controllers/CMSMain.php     |  8 ++----
 tests/controller/CMSMainTest.php | 45 ++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 6 deletions(-)

diff --git a/code/Controllers/CMSMain.php b/code/Controllers/CMSMain.php
index 6b3758e9..53441e9b 100644
--- a/code/Controllers/CMSMain.php
+++ b/code/Controllers/CMSMain.php
@@ -1006,12 +1006,8 @@ class CMSMain extends LeftAndMain implements CurrentPageIdentifier, PermissionPr
 
 		// Update the class instance if necessary
 		if(isset($data['ClassName']) && $data['ClassName'] != $record->ClassName) {
-			$newClassName = $record->ClassName;
-			// The records originally saved attribute was overwritten by $form->saveInto($record) before.
-			// This is necessary for newClassInstance() to work as expected, and trigger change detection
-			// on the ClassName attribute
-			$record->setClassName($data['ClassName']);
-			// Replace $record with a new instance
+			// Replace $record with a new instance of the new class
+			$newClassName = $data['ClassName'];
 			$record = $record->newClassInstance($newClassName);
 		}
 
diff --git a/tests/controller/CMSMainTest.php b/tests/controller/CMSMainTest.php
index ccd6ef1a..06d29345 100644
--- a/tests/controller/CMSMainTest.php
+++ b/tests/controller/CMSMainTest.php
@@ -2,6 +2,7 @@
 
 use SilverStripe\ORM\DB;
 use SilverStripe\ORM\DataObject;
+use SilverStripe\ORM\ValidationException;
 use SilverStripe\ORM\Versioning\Versioned;
 use SilverStripe\ORM\HiddenClass;
 use SilverStripe\CMS\Controllers\CMSMain;
@@ -540,14 +541,58 @@ class CMSMainTest extends FunctionalTest {
 		$this->assertContains("delete", $exemptActions);
 		$this->assertContains("unpublish", $exemptActions);
 	}
+
+	/**
+	 * Test that changed classes save with the correct class name
+	 */
+	public function testChangeClass() {
+		$this->logInWithPermission('ADMIN');
+		$cms = new CMSMain();
+		$page = new CMSMainTest_ClassA();
+		$page->Title = 'Class A';
+		$page->write();
+
+		$form = $cms->getEditForm($page->ID);
+		$form->loadDataFrom(['ClassName' => 'CMSMainTest_ClassB']);
+		$result = $cms->save([
+			'ID' => $page->ID,
+			'ClassName' => 'CMSMainTest_ClassB'
+		], $form);
+		$this->assertEquals(200, $result->getStatusCode());
+
+		$newPage = SiteTree::get()->byID($page->ID);
+
+		$this->assertInstanceOf('CMSMainTest_ClassB', $newPage);
+		$this->assertEquals('CMSMainTest_ClassB', $newPage->ClassName);
+		$this->assertEquals('Class A', $newPage->Title);
+
+	}
 }
 
 class CMSMainTest_ClassA extends Page implements TestOnly {
 	private static $allowed_children = array('CMSMainTest_ClassB');
+
+	protected function onBeforeWrite()
+	{
+		parent::onBeforeWrite();
+
+		if ($this->ClassName !== __CLASS__) {
+			throw new ValidationException("Class saved with incorrect ClassName");
+		}
+	}
 }
 
 class CMSMainTest_ClassB extends Page implements TestOnly {
 
+	protected function onBeforeWrite()
+	{
+		parent::onBeforeWrite();
+
+		if ($this->ClassName !== __CLASS__) {
+			throw new ValidationException("Class saved with incorrect ClassName");
+		}
+	}
+
 }
 
 class CMSMainTest_NotRoot extends Page implements TestOnly {