Fix incorrect handling of inflections in InflectedRoute

When inflecting plugin/controller names in URL params we must also
ensure that default values have been inflected in the same way or match
failures will occur.

Refs #4120

src/Routing/Route/InflectedRoute.php

@@ -23,6 +23,16 @@
  */
 class InflectedRoute extends Route {
 
+/**
+ * Flag for tracking whether or not the defaults have been inflected.
+ *
+ * Default values need to be inflected so that they match the inflections that match()
+ * will create.
+ *
+ * @var bool
+ */
+	protected $_inflectedDefaults = false;
+
 /**
  * Parses a string URL into an array. If it mathes, it will convert the prefix, controller and
  * plugin keys to their camelized form
@@ -55,13 +65,28 @@ public function parse($url) {
  * @return mixed either false or a string URL.
  */
 	public function match(array $url, array $context = array()) {
+		$url = $this->_underscore($url);
+		if (!$this->_inflectedDefaults) {
+			$this->_inflectedDefaults = true;
+			$this->defaults = $this->_underscore($this->defaults);
+		}
+		return parent::match($url, $context);
+	}
+
+/**
+ * Helper method for underscoring keys in a URL array.
+ *
+ * @param array $url An array of URL keys.
+ * @return array
+ */
+	protected function _underscore($url) {
 		if (!empty($url['controller'])) {
 			$url['controller'] = Inflector::underscore($url['controller']);
 		}
 		if (!empty($url['plugin'])) {
 			$url['plugin'] = Inflector::underscore($url['plugin']);
 		}
-		return parent::match($url, $context);
+		return $url;
 	}
 
 }

tests/TestCase/Routing/RouterTest.php

@@ -981,6 +981,22 @@ public function testUrlGenerationWithPrefix() {
 		$this->assertEquals($expected, $result);
 	}
 
+/**
+ * Test URL generation inside a prefixed plugin.
+ *
+ * @return void
+ */
+	public function testUrlGenerationPrefixedPlugin() {
+		Router::prefix('admin', function($routes) {
+			$routes->plugin('MyPlugin', function($routes) {
+				$routes->fallbacks();
+			});
+		});
+		$result = Router::url(['prefix' => 'admin', 'plugin' => 'MyPlugin', 'controller' => 'Forms', 'action' => 'edit', 2]);
+		$expected = '/admin/my_plugin/forms/edit/2';
+		$this->assertEquals($expected, $result);
+	}
+
 /**
  * testUrlGenerationWithExtensions method
  *