Symfony: [Config] Array nodes with default values aren't validated

[wouterj]

| Q | A
| ---------------- | -----
| Bug report? | yes
| Feature request? | no
| BC Break report? | no
| RFC? | no
| Symfony version | all

The Scenario

We have an ivory_ckeditor option with 2 childs: enabled and config_name. The config_name option has to be defined when the enabled option is true, however can be left out when enabled is false.

To achieve this, we've defined the following structure:

$root
    ->children()
        ->arrayNode('bundles')
            ->isRequired()
            ->children()
                ->arrayNode('content')
                    ->addDefaultsIfNotSet()
                    ->canBeEnabled()
                    ->children()
                        ->arrayNode('ivory_ckeditor')
                            ->addDefaultsIfNotSet()
                            ->treatFalseLike(['enabled' => false])
                            ->treatTrueLike(['enabled' => true])
                            ->treatNullLike(['enabled' => 'auto'])
                            ->validate()
                                ->ifTrue(function ($v) { return false !== $v['enabled'] && !isset($v['config_name']); })
                                ->thenInvalid('The config_name option has to be defined if CKEditor integration is enabled.')
                            ->end()
                            ->children()
                                ->enumNode('enabled')
                                    ->values([true, false, 'auto'])
                                    ->defaultValue('auto')
                                ->end()
                                ->scalarNode('config_name')->end()
                            ->end()
                        ->end() // ivory_ckeditor
                    ->end()
                ->end() // content
            ->end()
        ->end() // bundles
    ->end()
;

Test Case

Given the following configuration:

acme:
    bundles:
        content: ~

Then I would expect an error: The config_name option has to be defined if CKEditor integration is enabled.

Instead, no error is reported. In fact, the complete ->validate() rule is not executed.

The explanation

As soon as setDefaultsIfNotSet() is used and there are default values, validation is skipped (see the code).

While it seems logical that a default value is valid and thus doesn't need validation, this can't be applied 100% for array nodes: Some children might not have a default value and need to be validated.

Proposal

I would propose to always run validation, even if default values apply. As this might break applications, we need to add a flag to ArrayNodeBuilder to enable this validation, triggering a deprecation when it disables. Much like the choices_as_value option in the choice form type was handled.

[curry684]

Instead of a flag I would for now prefer triggering the errors as warnings and switch them to errors in 4.0. That keeps it within BC promise.

[carsonbot]

Hey, thanks for your report!
There has not been a lot of activity here for a while. Is this bug still relevant? Have you managed to find a workaround?

[wouterj]

Not sure, can't reproduce this anymore (and I don't understand my previous code reference). Let's close