[FEATURE] Allow default content on optional f:render

Whenever `f:render` is called and the `optional` flag is set to `TRUE`, rendering a missing section results in an empty output. Instead of rendering this empty output, a new attribute `default` (mixed) is added and can be filled with a fallback-type default value. Alternatively, the tag content can be used to define this default value like so many other content/attribute-flexible ViewHelpers.

src/ViewHelpers/RenderViewHelper.php

@@ -82,6 +82,7 @@ public function initializeArguments() {
 		$this->registerArgument('partial', 'string', 'Partial to render, with or without section', FALSE, NULL);
 		$this->registerArgument('arguments', 'array', 'Array of variables to be transferred. Use {_all} for all variables', FALSE, array());
 		$this->registerArgument('optional', 'boolean', 'If TRUE, considers the *section* optional. Partial never is.', FALSE, FALSE);
+		$this->registerArgument('default', 'mixed', 'Value (usually string) to be displayed if the section or partial does not exist', FALSE, NULL);
 	}
 
 	/**
@@ -95,12 +96,22 @@ public function render() {
 		$partial = $this->arguments['partial'];
 		$arguments = (array) $this->arguments['arguments'];
 		$optional = (boolean) $this->arguments['optional'];
+		$content = '';
 		if ($partial !== NULL) {
-			return $this->viewHelperVariableContainer->getView()->renderPartial($partial, $section, $arguments, $optional);
+			$content = $this->viewHelperVariableContainer->getView()->renderPartial($partial, $section, $arguments, $optional);
 		} elseif ($section !== NULL) {
-			return $this->viewHelperVariableContainer->getView()->renderSection($section, $arguments, $optional);
+			$content = $this->viewHelperVariableContainer->getView()->renderSection($section, $arguments, $optional);
 		}
-		return '';
+		// Replace empty content with default value. If default is
+		// not set, NULL is returned and cast to a new, empty string
+		// outside of this ViewHelper.
+		if ('' === $content) {
+			$content = $this->arguments['default'];
+			if (NULL === $content) {
+				$content = $this->renderChildren();
+			}
+		}
+		return $content;
 	}
 
 }

tests/Unit/ViewHelpers/RenderViewHelperTest.php

@@ -24,6 +24,7 @@ public function testInitializeArgumentsRegistersExpectedArguments() {
 		$instance->expects($this->at(1))->method('registerArgument')->with('partial', 'string', $this->anything(), FALSE, NULL);
 		$instance->expects($this->at(2))->method('registerArgument')->with('arguments', 'array', $this->anything(), FALSE, array());
 		$instance->expects($this->at(3))->method('registerArgument')->with('optional', 'boolean', $this->anything(), FALSE, FALSE);
+		$instance->expects($this->at(4))->method('registerArgument')->with('default', 'mixed', $this->anything(), FALSE, FALSE);
 		$instance->initializeArguments();
 	}
 
@@ -39,10 +40,13 @@ public function testRender(array $arguments, $expectedViewMethod) {
 		} else {
 			$methods = array('renderPartial', 'renderSection');
 		}
-		$instance = new RenderViewHelper();
+		$instance = $this->getMock('NamelessCoder\\Fluid\\ViewHelpers\\RenderViewHelper', array('renderChildren'));
+		$instance->expects($this->any())->method('renderChildren')->willReturn(NULL);
 		$renderingContext = new RenderingContext();
+		$paths = $this->getMock('NamelessCoder\\Fluid\\View\\TemplatePaths', array('sanitizePath'));
+		$paths->expects($this->any())->method('sanitizePath')->willReturnArgument(0);
 		$viewHelperVariableContainer = new ViewHelperVariableContainer();
-		$view = $this->getMock('NamelessCoder\\Fluid\\View\\TemplateView', $methods, array(), '', FALSE);
+		$view = $this->getMock('NamelessCoder\\Fluid\\View\\TemplateView', $methods, array($paths, $renderingContext));
 		$viewHelperVariableContainer->setView($view);
 		$renderingContext->injectViewHelperVariableContainer($viewHelperVariableContainer);
 		$instance->setArguments($arguments);
@@ -57,19 +61,19 @@ public function testRender(array $arguments, $expectedViewMethod) {
 	public function getRenderTestValues() {
 		return array(
 			array(
-				array('partial' => NULL, 'section' => NULL, 'arguments' => array(), 'optional' => FALSE),
+				array('partial' => NULL, 'section' => NULL, 'arguments' => array(), 'optional' => FALSE, 'default' => NULL),
 				NULL
 			),
 			array(
-				array('partial' => 'foo-partial', 'section' => NULL, 'arguments' => array(), 'optional' => FALSE),
+				array('partial' => 'foo-partial', 'section' => NULL, 'arguments' => array(), 'optional' => FALSE, 'default' => NULL),
 				'renderPartial'
 			),
 			array(
-				array('partial' => 'foo-partial', 'section' => 'foo-section', 'arguments' => array(), 'optional' => FALSE),
+				array('partial' => 'foo-partial', 'section' => 'foo-section', 'arguments' => array(), 'optional' => FALSE, 'default' => NULL),
 				'renderPartial'
 			),
 			array(
-				array('partial' => NULL, 'section' => 'foo-section', 'arguments' => array(), 'optional' => FALSE),
+				array('partial' => NULL, 'section' => 'foo-section', 'arguments' => array(), 'optional' => FALSE, 'default' => NULL),
 				'renderSection'
 			),
 		);