bug #29894 [DependencyInjection] the string "0" is a valid service id…

…entifier (xabbuh)

This PR was merged into the 3.4 branch.

Discussion
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[DependencyInjection] the string "0" is a valid service identifier

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #29854
| License       | MIT
| Doc PR        |

Commits
-------

caca373 the string "0" is a valid service identifier

src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php

@@ -496,7 +496,7 @@ private function getArgumentsAsPhp(\DOMElement $node, $name, $file, $lowercase =
 
             switch ($arg->getAttribute('type')) {
                 case 'service':
-                    if (!$arg->getAttribute('id')) {
+                    if ('' === $arg->getAttribute('id')) {
                         throw new InvalidArgumentException(sprintf('Tag "<%s>" with type="service" has no or empty "id" attribute in "%s".', $name, $file));
                     }
                     if ($arg->hasAttribute('strict')) {
@@ -549,7 +549,7 @@ private function getArgumentsAsPhp(\DOMElement $node, $name, $file, $lowercase =
      * @param \DOMNode $node
      * @param mixed    $name
      *
-     * @return array
+     * @return \DOMElement[]
      */
     private function getChildren(\DOMNode $node, $name)
     {

src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/services6.xml

@@ -61,5 +61,9 @@
     </service>
     <service id="alias_for_foo" alias="foo" />
     <service id="another_alias_for_foo" alias="foo" public="false" />
+    <service id="0" class="FooClass" />
+    <service id="1" class="FooClass">
+      <argument type="service" id="0" />
+    </service>
   </services>
 </container>