addDefaultChildrenIfNoneSet example

$this->addMailerSection($rootNode);

        return $treeBuilder;
    }

    private function addFormThemesSection(ArrayNodeDefinition $rootNode): void
    {
        $rootNode
            ->fixXmlConfig('form_theme')
            ->children()
                ->arrayNode('form_themes')
                    ->addDefaultChildrenIfNoneSet()
                    ->prototype('scalar')->defaultValue('form_div_layout.html.twig')->end()
                    ->example(['@My/form.html.twig'])
                    ->validate()
                        ->ifTrue(fn ($v) => !\in_array('form_div_layout.html.twig', $v))
                        ->then(fn ($v) => array_merge(['form_div_layout.html.twig'], $v))
                    ->end()
                ->end()
            ->end()
        ;
    }

    

->prototype('array')
        ;
        $node->getNode();
    }

    public function testPrototypeNodesCantHaveADefaultValueWhenUsingDefaultChildren()
    {
        $this->expectException(InvalidDefinitionException::class);
        $node = new ArrayNodeDefinition('root');
        $node
            ->defaultValue([])
            ->addDefaultChildrenIfNoneSet('foo')
            ->prototype('array')
        ;
        $node->getNode();
    }

    public function testPrototypedArrayNodeDefaultWhenUsingDefaultChildren()
    {
        $node = new ArrayNodeDefinition('root');
        $node
            ->addDefaultChildrenIfNoneSet()
            ->prototype('array')
        ;