deprecate implicit string casting of mapping keys

Author: xabbuh

Loader/YamlFileLoader.php

@@ -17,6 +17,7 @@
 use Symfony\Component\Yaml\Exception\ParseException;
 use Symfony\Component\Yaml\Parser as YamlParser;
 use Symfony\Component\Config\Loader\FileLoader;
+use Symfony\Component\Yaml\Yaml;
 
 /**
  * YamlFileLoader loads Yaml routing files.
@@ -58,7 +59,7 @@ public function load($file, $type = null)
         }
 
         try {
-            $parsedConfig = $this->yamlParser->parse(file_get_contents($path));
+            $parsedConfig = $this->yamlParser->parse(file_get_contents($path), Yaml::PARSE_KEYS_AS_STRINGS);
         } catch (ParseException $e) {
             throw new \InvalidArgumentException(sprintf('The file "%s" does not contain valid YAML.', $path), 0, $e);
         }

composer.json

@@ -21,15 +21,16 @@
     "require-dev": {
         "symfony/config": "~2.8|~3.0",
         "symfony/http-foundation": "~2.8|~3.0",
-        "symfony/yaml": "~2.8|~3.0",
+        "symfony/yaml": "~3.3",
         "symfony/expression-language": "~2.8|~3.0",
         "symfony/dependency-injection": "~2.8|~3.0",
         "doctrine/annotations": "~1.0",
         "doctrine/common": "~2.2",
         "psr/log": "~1.0"
     },
     "conflict": {
-        "symfony/config": "<2.8"
+        "symfony/config": "<2.8",
+        "symfony/yaml": "<3.3"
     },
     "suggest": {
         "symfony/http-foundation": "For using a Symfony Request object",