bug #17687 Improved the error message when using "@" in a decorated service (javiereguiluz)

This PR was squashed before being merged into the 2.7 branch (closes #17687).

Discussion
----------

Improved the error message when using "@" in a decorated service

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #17666
| License       | MIT
| Doc PR        | -

Commits
-------

e7690ba Improved the error message when using "@" in a decorated service

Author: fabpot

Loader/YamlFileLoader.php

@@ -288,6 +288,10 @@ private function parseDefinition($id, $service, $file)
         }
 
         if (isset($service['decorates'])) {
+            if ('' !== $service['decorates'] && '@' === $service['decorates'][0]) {
+                throw new InvalidArgumentException(sprintf('The value of the "decorates" option for the "%s" service must be the id of the service without the "@" prefix (replace "%s" with "%s").', $id, $service['decorates'], substr($service['decorates'], 1)));
+            }
+
             $renameId = isset($service['decoration_inner_name']) ? $service['decoration_inner_name'] : null;
             $definition->setDecoratedService($service['decorates'], $renameId);
         }

Tests/Fixtures/yaml/bad_decorates.yml

@@ -0,0 +1,7 @@
+services:
+    foo:
+        class: stdClass
+    bar:
+        class: stdClass
+        decorates: "@foo"
+        arguments: ["@bar.inner"]

Tests/Loader/YamlFileLoaderTest.php

@@ -297,4 +297,14 @@ public function testTagWithNonStringNameThrowsException()
         $loader = new YamlFileLoader(new ContainerBuilder(), new FileLocator(self::$fixturesPath.'/yaml'));
         $loader->load('tag_name_no_string.yml');
     }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\InvalidArgumentException
+     * @expectedExceptionMessage The value of the "decorates" option for the "bar" service must be the id of the service without the "@" prefix (replace "@foo" with "foo").
+     */
+    public function testDecoratedServicesWithWrongSyntaxThrowsException()
+    {
+        $loader = new YamlFileLoader(new ContainerBuilder(), new FileLocator(self::$fixturesPath.'/yaml'));
+        $loader->load('bad_decorates.yml');
+    }
 }