BUG Ensure errorpage is built in live mode

Fixes https://github.com/silverstripe/silverstripe-framework/issues/8110

code/model/ErrorPage.php

@@ -105,15 +105,31 @@ class ErrorPage extends Page {
 				);
 				$pageExists = ($page && $page->exists());
 				$pagePath = self::get_filepath_for_errorcode($code);
-				if(!($pageExists && file_exists($pagePath))) {
+				if(!$pageExists || !file_exists($pagePath)) {
 					if(!$pageExists) {
 						$page = new ErrorPage($defaultData);
 						$page->write();
 						$page->publish('Stage', 'Live');
 					}
 
+					// Skip unpublished records
+					/** @var ErrorPage $livePage */
+					$livePage = Versioned::get_by_stage('ErrorPage', Versioned::LIVE)
+						->byID($page->ID);
+					if (!$livePage) {
+						continue;
+					}
+
 					// Ensure a static error page is created from latest error page content
-					$response = Director::test(Director::makeRelative($page->Link()));
+					$origReadingMode = static::get_reading_mode();
+					$oldDefault = static::get_default_reading_mode();
+					Versioned::reading_stage(Versioned::LIVE);
+					Versioned::set_default_reading_mode(Versioned::get_reading_mode());
+					$response = Director::test(Director::makeRelative($livePage->Link()));
+					static::set_default_reading_mode($oldDefault);
+					static::set_reading_mode($origReadingMode);
+
+					// Write contents
 					$written = null;
 					if($fh = fopen($pagePath, 'w')) {
 						$written = fwrite($fh, $response->getBody());

tests/model/ErrorPageTest.php

@@ -88,4 +88,34 @@ class ErrorPageTest extends FunctionalTest {
 		$this->assertNotNull($response->getBody());
 		$this->assertContains('text/html', $response->getHeader('Content-Type'));
 	}
+
+	public function testRequireDefaultRecords()
+	{
+		$this->logInWithPermission('ADMIN');
+		Config::inst()->update('ErrorPage', 'static_filepath', ASSETS_PATH . '/erropagetest');
+		Filesystem::makeFolder(ASSETS_PATH . '/erropagetest');
+
+		// Ensure 404 page is published
+		/** @var ErrorPage $page404 */
+		$page404 = $this->objFromFixture('ErrorPage', '404');
+		$page404->publish('Stage', 'Live');
+
+		// Ensure 500 page isn't pubilshed
+		/** @var ErrorPage $page500 */
+		$page500 = $this->objFromFixture('ErrorPage', '500');
+		$page500->doUnpublish();
+
+		// Run regeneration
+		/** @var ErrorPage $singleton */
+		$singleton = singleton('ErrorPage');
+		$singleton->requireDefaultRecords();
+
+		// 404 page exists
+		$path404 = ErrorPage::get_filepath_for_errorcode(404);
+		$this->assertFileExists($path404);
+
+		// 500 doesn't exist due to it being unpubilshed
+		$path500 = ErrorPage::get_filepath_for_errorcode(500);
+		$this->assertFileNotExists($path500);
+	}
 }

tests/model/ErrorPageTest.yml

@@ -4,6 +4,11 @@ ErrorPage:
       URLSegment: page-not-found
       Content: My error page body
       ErrorCode: 404
+   500:
+      Title: Server error
+      URLSegment: server-error
+      Content: My error page body
+      ErrorCode: 500
    403:
       Title: Permission Failure
       URLSegment: permission-denied