API Make SSViewer#process return HTMLText not string

This means that you dont have to worry about casting it
as HTMLText again when using the result in a template or other context

However in some situations code might be assuming it can
check with is_string, in which case you now need to use instanceof HTMLText

control/Controller.php

@@ -157,9 +157,9 @@ class Controller extends RequestHandler implements TemplateGlobalProvider {
 					. "returning it without modification.");
 			}
 			$this->response = $body;
-			
+
 		} else {
-			if(is_object($body)) {
+			if($body instanceof Object && $body->hasMethod('getViewer')) {
 				if(isset($_REQUEST['debug_request'])) {
 					Debug::message("Request handler $body->class object to $this->class controller;"
 						. "rendering with template returned by $body->class::getViewer()");

control/HTTPResponse.php

@@ -159,7 +159,7 @@ class SS_HTTPResponse {
 	 * @return SS_HTTPRequest $this
 	 */
 	public function setBody($body) {
-		$this->body = $body;
+		$this->body = $body ? (string)$body : $body; // Don't type-cast false-ish values, eg null is null not ''
 	}
 	
 	/**

control/PjaxResponseNegotiator.php

@@ -79,7 +79,8 @@ class PjaxResponseNegotiator {
 		// Execute the fragment callbacks and build the response.
 		foreach($fragments as $fragment) {
 			if(isset($callbacks[$fragment])) {
-				$responseParts[$fragment] = call_user_func($callbacks[$fragment]);
+				$res = call_user_func($callbacks[$fragment]);
+				$responseParts[$fragment] = $res ? (string)$res : $res;
 			} else {
 				throw new SS_HTTPResponse_Exception("X-Pjax = '$fragment' not supported for this URL.", 400);
 			}

dev/SapphireTest.php

@@ -510,6 +510,17 @@ class SapphireTest extends PHPUnit_Framework_TestCase {
 			$controller->response->removeHeader('Location');
 		}
 	}
+
+	public static function assertContains($needle, $haystack, $message = '', $ignoreCase = FALSE, $checkForObjectIdentity = TRUE) {
+		if ($haystack instanceof DBField) $haystack = (string)$haystack;
+		parent::assertContains($needle, $haystack, $message, $ignoreCase, $checkForObjectIdentity);
+	}
+
+	public static function assertNotContains($needle, $haystack, $message = '', $ignoreCase = FALSE, $checkForObjectIdentity = TRUE) {
+		if ($haystack instanceof DBField) $haystack = (string)$haystack;
+		parent::assertNotContains($needle, $haystack, $message, $ignoreCase, $checkForObjectIdentity);
+	}
+
 	/**
 	 * Clear the log of emails sent
 	 */

model/fieldtypes/DBField.php

@@ -295,5 +295,8 @@ abstract class DBField extends ViewableData {
 </ul>
 DBG;
 	}
-	
+
+	public function __toString() {
+		return $this->forTemplate();
+	}
 }

view/SSViewer.php

@@ -866,7 +866,7 @@ class SSViewer {
 	 * @param ViewableData $item
 	 * @param SS_Cache $cache Optional cache backend.
 	 *
-	 * @return String Parsed template output.
+	 * @return HTMLText Parsed template output.
 	 */
 	public function process($item, $arguments = null) {
 		SSViewer::$topLevel[] = $item;
@@ -909,12 +909,7 @@ class SSViewer {
 				$subtemplateViewer->includeRequirements(false);
 				$subtemplateViewer->setPartialCacheStore($this->getPartialCacheStore());
 
-				$underlay[$subtemplate] = DBField::create_field(
-					'HTMLText',
-					$subtemplateViewer->process($item, $arguments),
-					$subtemplate,
-					array('shortcodes' => false)
-				);
+				$underlay[$subtemplate] = $subtemplateViewer->process($item, $arguments);
 			}
 		}
 
@@ -939,7 +934,7 @@ class SSViewer {
 			}
 		}
 
-		return $output;
+		return DBField::create_field('HTMLText', $output, null, array('shortcodes' => false));
 	}
 
 	/**

view/ViewableData.php

@@ -318,7 +318,7 @@ class ViewableData extends Object implements IteratorAggregate {
 	 *
 	 * @param string|array|SSViewer $template the template to render into
 	 * @param array $customFields fields to customise() the object with before rendering
-	 * @return string
+	 * @return HTMLText
 	 */
 	public function renderWith($template, $customFields = null) {
 		if(!is_object($template)) {