[Config] Fix Yaml dumper for prototyped array with default null

Author: GromNaN

src/Symfony/Bundle/FrameworkBundle/Tests/Functional/ConfigDumpReferenceCommandTest.php

@@ -115,6 +115,17 @@ public function testDumpAtPathXml(bool $debug)
         $this->assertStringContainsString('[ERROR] The "path" option is only available for the "yaml" format.', $tester->getDisplay());
     }
 
+    #[TestWith(['yaml'])]
+    #[TestWith(['xml'])]
+    public function testDumpFrameworkBundle(string $format)
+    {
+        $tester = $this->createCommandTester(true);
+        $ret = $tester->execute(['name' => 'framework', '--format' => $format]);
+
+        $this->assertSame(0, $ret, 'Returns 0 in case of success');
+        $this->assertStringContainsString('%env(default::SYMFONY_TRUSTED_PROXIES)%', $tester->getDisplay());
+    }
+
     #[DataProvider('provideCompletionSuggestions')]
     public function testComplete(bool $debug, array $input, array $expectedSuggestions)
     {

src/Symfony/Component/Config/Definition/Dumper/YamlReferenceDumper.php

@@ -89,8 +89,8 @@ private function writeNode(NodeInterface $node, ?NodeInterface $parentNode = nul
                 $children = $this->getPrototypeChildren($node);
             }
 
-            if (!$children && !($node->hasDefaultValue() && \count($defaultArray = $node->getDefaultValue()))) {
-                $default = '[]';
+            if (!$children && !($node->hasDefaultValue() && $defaultArray = $node->getDefaultValue())) {
+                $default = $node->hasDefaultValue() && null === $defaultArray ? '~' : '[]';
             }
         } elseif ($node instanceof EnumNode) {
             $comments[] = 'One of '.$node->getPermissibleValues('; ');

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

@@ -119,7 +119,7 @@ public function setAddChildrenIfNoneSet(int|string|array|null $children = ['defa
     }
 
     /**
-     * The default value could be either explicited or derived from the prototype
+     * The default value could be either explicit or derived from the prototype
      * default value.
      */
     public function getDefaultValue(): mixed

src/Symfony/Component/Config/Tests/Definition/Dumper/XmlReferenceDumperTest.php

@@ -82,6 +82,9 @@ enum-with-class=""
                 <!-- prototype -->
                 <scalar-prototyped>scalar value</scalar-prototyped>
 
+                <!-- prototype -->
+                <string-list-default-null>value</string-list-default-null>
+
                 <!-- prototype: Parameter name -->
                 <parameter name="parameter name">scalar value</parameter>
 

src/Symfony/Component/Config/Tests/Definition/Dumper/YamlReferenceDumperTest.php

@@ -115,6 +115,7 @@ enum_with_class:      ~ # One of foo; bar
                     # which should be indented
                     child3:               ~ # Example: 'example setting'
                 scalar_prototyped:    []
+                string_list_default_null: ~
                 variable:             ~
 
                     # Examples:

src/Symfony/Component/Config/Tests/Fixtures/Configuration/ExampleConfiguration.php

@@ -62,6 +62,10 @@ public function getConfigTreeBuilder(): TreeBuilder
                 ->arrayNode('scalar_prototyped')
                     ->prototype('scalar')->end()
                 ->end()
+                ->arrayNode('string_list_default_null')
+                    ->defaultNull()
+                    ->stringPrototype()->end()
+                ->end()
                 ->variableNode('variable')
                     ->example(['foo', 'bar'])
                 ->end()