adjusted I18N to be consistent with intl message formatting

docs/guide/i18n.md

@@ -53,6 +53,9 @@ TBD: https://github.com/yiisoft/yii2/issues/930
 
 ### Named placeholders
 
+You can add parameters to a translation message that will be substituted with the corresponding value after translation.
+The format for this is to use curly brackets around the parameter name as you can see in the following example:
+
 ```php
 $username = 'Alexander';
 echo \Yii::t('app', 'Hello, {username}!', array(
@@ -60,6 +63,8 @@ echo \Yii::t('app', 'Hello, {username}!', array(
 ));
 ```
 
+Note that the parameter assignment is without the brackets.
+
 ### Positional placeholders
 
 ```php

framework/yii/i18n/I18N.php

@@ -73,24 +73,31 @@ class I18N extends Component
 	public function translate($category, $message, $params, $language)
 	{
 		$message = $this->getMessageSource($category)->translate($category, $message, $language);
-		$params = (array)$params;
+		if (empty($params)) {
+			return $message;
+		}
 
+		$params = (array)$params;
 		if (class_exists('MessageFormatter', false) && preg_match('~{\s*[\d\w]+\s*,~u', $message)) {
 			$formatter = new MessageFormatter($language, $message);
 			if ($formatter === null) {
-				\Yii::$app->getLog()->log("$language message from category $category failed. Message is: $message.", Logger::LEVEL_WARNING, 'application');
-			}
+				\Yii::$app->getLog()->log("$language message from category $category is invalid. Message is: $message.", Logger::LEVEL_WARNING, 'application');
+			} else {
 				$result = $formatter->format($params);
 				if ($result === false) {
 					$errorMessage = $formatter->getErrorMessage();
 					\Yii::$app->getLog()->log("$language message from category $category failed with error: $errorMessage. Message is: $message.", Logger::LEVEL_WARNING, 'application');
-			}
-			else {
+				} else {
 					return $result;
 				}
 			}
+		}
 
-		return empty($params) ? $message : strtr($message, $params);
+		$p = array();
+		foreach($params as $name => $value) {
+			$p['{' . $name . '}'] = $value;
+		}
+		return strtr($message, $p);
 	}
 
 	/**

tests/unit/data/i18n/messages/de_DE/test.php

+<?php
+/**
+ *
+ */
+return array(
+	'The dog runs fast.' => 'Der Hund rennt schnell.',
+	'His speed is about {n} km/h.' => 'Seine Geschwindigkeit beträgt {n} km/h.',
+	'His name is {name} and his speed is about {n, number} km/h.' => 'Er heißt {name} und ist {n, number} km/h schnell.',
+);
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tests/unit/data/i18n/messages/en_US/test.php

+<?php
+/**
+ *
+ */
+return array(
+	'The dog runs fast.' => 'Der Hund rennt schell.',
+);
\ No newline at end of file

tests/unit/framework/i18n/I18NTest.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yiiunit\framework\i18n;
+
+use yii\i18n\I18N;
+use yii\i18n\MessageFormatter;
+use yii\i18n\PhpMessageSource;
+use yiiunit\TestCase;
+
+/**
+ * @author Carsten Brandt <mail@cebe.cc>
+ * @since 2.0
+ * @group i18n
+ */
+class I18NTest extends TestCase
+{
+	/**
+	 * @var I18N
+	 */
+	public $i18n;
+
+	protected function setUp()
+	{
+		parent::setUp();
+		$this->mockApplication();
+		$this->i18n = new I18N(array(
+			'translations' => array(
+				'test' => new PhpMessageSource(array(
+					'basePath' => '@yiiunit/data/i18n/messages',
+				))
+			)
+		));
+	}
+
+	public function testTranslate()
+	{
+		$msg = 'The dog runs fast.';
+		$this->assertEquals('The dog runs fast.', $this->i18n->translate('test', $msg, array(), 'en_US'));
+		$this->assertEquals('Der Hund rennt schnell.', $this->i18n->translate('test', $msg, array(), 'de_DE'));
+	}
+
+	public function testTranslateParams()
+	{
+		$msg = 'His speed is about {n} km/h.';
+		$params = array(
+			'n' => 42,
+		);
+		$this->assertEquals('His speed is about 42 km/h.', $this->i18n->translate('test', $msg, $params, 'en_US'));
+		$this->assertEquals('Seine Geschwindigkeit beträgt 42 km/h.', $this->i18n->translate('test', $msg, $params, 'de_DE'));
+
+		$msg = 'His name is {name} and his speed is about {n, number} km/h.';
+		$params = array(
+			'n' => 42,
+			'name' => 'DA VINCI', // http://petrix.com/dognames/d.html
+		);
+		$this->assertEquals('His name is DA VINCI and his speed is about 42 km/h.', $this->i18n->translate('test', $msg, $params, 'en_US'));
+		$this->assertEquals('Er heißt DA VINCI und ist 42 km/h schnell.', $this->i18n->translate('test', $msg, $params, 'de_DE'));
+	}
+
+}
\ No newline at end of file

tests/unit/framework/i18n/MessageFormatterTest.php

@@ -140,4 +140,23 @@ _MSG_
 
 		$this->assertEquals($expected, $result);
 	}
+
+	/**
+	 * when instantiating a MessageFormatter with invalid pattern it should be null
+	 */
+	public function testNullConstructor()
+	{
+		$this->assertNull(new MessageFormatter('en_US', ''));
+	}
+
+	public function testNoParams()
+	{
+		$pattern = '{'.self::SUBJECT.'} is '.self::N;
+		$result = MessageFormatter::formatMessage('en_US', $pattern, array());
+		$this->assertEquals($pattern, $result);
+
+		$formatter = new MessageFormatter('en_US', $pattern);
+		$result = $formatter->format(array());
+		$this->assertEquals($pattern, $result);
+	}
 }
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