Making Cache::write() trigger warnings when a cache engine returns fa…

…lse from a write. Tests added. Fixes #877

cake/libs/cache.php

@@ -270,6 +270,12 @@ public static function write($key, $value, $config = null) {
 
 		$success = self::$_engines[$config]->write($settings['prefix'] . $key, $value, $settings['duration']);
 		self::set();
+		if ($success === false) {
+			trigger_error(
+				sprintf(__("%s cache was unable to write '%s' to cache", true), $config, $key),
+				E_USER_WARNING
+			);
+		}
 		return $success;
 	}
 

cake/tests/cases/libs/cache.test.php

@@ -309,6 +309,28 @@ function testWriteEmptyValues() {
 		$this->assertIdentical(Cache::read('App.zeroTest2'), '0');
 	}
 
+/**
+ * Test that failed writes cause errors to be triggered.
+ *
+ * @return void
+ */
+	function testWriteTriggerError() {
+		App::build(array(
+			'libs' => array(TEST_CAKE_CORE_INCLUDE_PATH . 'tests' . DS . 'test_app' . DS . 'libs' . DS),
+			'plugins' => array(TEST_CAKE_CORE_INCLUDE_PATH . 'tests' . DS . 'test_app' . DS . 'plugins' . DS)
+		), true);
+
+		Cache::config('test_trigger', array('engine' => 'TestAppCache'));
+		try {
+			Cache::write('fail', 'value', 'test_trigger');
+			$this->fail('No exception thrown');
+		} catch (PHPUnit_Framework_Error $e) {
+			$this->assertTrue(true);
+		}
+		Cache::drop('test_trigger');
+		App::build();
+	}
+
 /**
  * testCacheDisable method
  *

cake/tests/test_app/libs/cache/test_app_cache.php

@@ -19,7 +19,11 @@
  */
 class TestAppCacheEngine extends CacheEngine {
 
-	public function write($key, $value, $duration) { }
+	public function write($key, $value, $duration) { 
+		if ($key = 'fail') {
+			return false;
+		}
+	}
 
 	public function read($key) { }