feature(events): Adds static methods for returning common values

These functions are particularly useful as handlers for events/hooks.

engine/classes/Elgg/Values.php

@@ -0,0 +1,48 @@
+<?php
+namespace Elgg;
+
+/**
+ * Functions for use as plugin hook/event handlers or other situations where you need a
+ * globally accessible callable.
+ */
+class Values {
+
+	/**
+	 * Return true
+	 *
+	 * @return true
+	 * @since 1.12.0
+	 */
+	public static function getTrue() {
+		return true;
+	}
+
+	/**
+	 * Return false
+	 *
+	 * @return false
+	 * @since 1.12.0
+	 */
+	public static function getFalse() {
+		return false;
+	}
+
+	/**
+	 * Return null
+	 *
+	 * @return null
+	 * @since 1.12.0
+	 */
+	public static function getNull() {
+	}
+
+	/**
+	 * Return empty array
+	 *
+	 * @return array
+	 * @since 1.12.0
+	 */
+	public static function getArray() {
+		return [];
+	}
+}

engine/tests/phpunit/Elgg/EventsServiceTest.php

@@ -23,7 +23,7 @@ public function testTriggerCallsRegisteredHandlersAndReturnsTrue() {
 	public function testFalseStopsPropagationAndReturnsFalse() {
 		$events = new \Elgg\EventsService();
 
-		$events->registerHandler('foo', 'bar', array('\Elgg\EventsServiceTest', 'returnFalse'));
+		$events->registerHandler('foo', 'bar', 'Elgg\Values::getFalse');
 		$events->registerHandler('foo', 'bar', array($this, 'incrementCounter'));
 
 		$this->assertFalse($events->trigger('foo', 'bar'));
@@ -33,7 +33,7 @@ public function testFalseStopsPropagationAndReturnsFalse() {
 	public function testNullDoesNotStopPropagation() {
 		$events = new \Elgg\EventsService();
 
-		$events->registerHandler('foo', 'bar', array('\Elgg\EventsServiceTest', 'returnNull'));
+		$events->registerHandler('foo', 'bar', 'Elgg\Values::getNull');
 		$events->registerHandler('foo', 'bar', array($this, 'incrementCounter'));
 
 		$this->assertTrue($events->trigger('foo', 'bar'));
@@ -43,7 +43,7 @@ public function testNullDoesNotStopPropagation() {
 	public function testUnstoppableEventsCantBeStoppedAndReturnTrue() {
 		$events = new \Elgg\EventsService();
 
-		$events->registerHandler('foo', 'bar', array('\Elgg\EventsServiceTest', 'returnFalse'));
+		$events->registerHandler('foo', 'bar', 'Elgg\Values::getFalse');
 		$events->registerHandler('foo', 'bar', array($this, 'incrementCounter'));
 
 		$this->assertTrue($events->trigger('foo', 'bar', null, array(
@@ -69,17 +69,5 @@ public function incrementCounter() {
 		$this->counter++;
 		return true;
 	}
-
-	public static function returnTrue() {
-		return true;
-	}
-
-	public static function returnFalse() {
-		return false;
-	}
-
-	public static function returnNull() {
-		return;
-	}
 }
 

engine/tests/phpunit/Elgg/PluginHooksServiceTest.php

@@ -27,7 +27,7 @@ public function testCanPassParamsAndChangeReturnValue() {
 
 	public function testNullReturnDoesntChangeValue() {
 		$hooks = new \Elgg\PluginHooksService();
-		$hooks->registerHandler('foo', 'bar', array('\Elgg\PluginHooksServiceTest', 'returnNull'));
+		$hooks->registerHandler('foo', 'bar', 'Elgg\Values::getNull');
 
 		$returnval = $hooks->trigger('foo', 'bar', array(), 1);
 
@@ -46,10 +46,6 @@ public function testUncallableHandlersAreLogged() {
 
 		$hooks->trigger('foo', 'bar');
 	}
-
-	public static function returnTwo() {
-		return 2;
-	}
 
 	public static function changeReturn($foo, $bar, $returnval, $params) {
 		$testCase = $params['testCase'];
@@ -59,10 +55,6 @@ public static function changeReturn($foo, $bar, $returnval, $params) {
 		return 2;
 	}
 
-	public static function returnNull() {
-		return;
-	}
-
 	public static function throwInvalidArg() {
 		throw new \InvalidArgumentException();
 	}