bug #39764 [Config] fix handling float-like key attribute values (xabbuh)

This PR was merged into the 4.4 branch.

Discussion
----------

[Config]  fix handling float-like key attribute values

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | Fix #36001
| License       | MIT
| Doc PR        |

Commits
-------

a2ad4fa8b3 fix handling float-like key attribute values

src/Symfony/Component/Config/Definition/PrototypedArrayNode.php

@@ -237,6 +237,10 @@ class PrototypedArrayNode extends ArrayNode
                 } elseif (isset($v[$this->keyAttribute])) {
                     $k = $v[$this->keyAttribute];
 
+                    if (\is_float($k)) {
+                        $k = var_export($k, true);
+                    }
+
                     // remove the key attribute when required
                     if ($this->removeKeyAttribute) {
                         unset($v[$this->keyAttribute]);

src/Symfony/Component/Config/Tests/Definition/NormalizationTest.php

@@ -201,6 +201,32 @@ class NormalizationTest extends TestCase
         $this->assertNormalized($tree, $data, $data);
     }
 
+    public function testFloatLikeValueAsMapKeyAttribute()
+    {
+        $tree = (new TreeBuilder('root'))
+            ->getRootNode()
+                ->useAttributeAsKey('number')
+                ->arrayPrototype()
+                    ->children()
+                        ->scalarNode('foo')->end()
+                    ->end()
+                ->end()
+            ->end()
+            ->buildTree()
+        ;
+
+        $this->assertNormalized($tree, [
+            [
+                'number' => 3.0,
+                'foo' => 'bar',
+            ],
+        ], [
+            '3.0' => [
+                'foo' => 'bar',
+            ],
+        ]);
+    }
+
     public static function assertNormalized(NodeInterface $tree, $denormalized, $normalized)
     {
         self::assertSame($normalized, $tree->normalize($denormalized));