Filament how to validate CheckboxList value that exists in database

@RemiM tired your code, and modified one of the checkbox value in browser dev tools

->rules([
    'required',
    'array',
    'exists:regions,id',
]),

i don't understand why this works without use regions.*

the field is required, is array, and the array is exists in regions ? look weird o.0

in the https://filamentphp.com/docs/3.x/forms/validation there is nothing about nested and no distinct rule

@newbie360 I think you can add the distinct to the rules array as well.

As for why it works:

• Filament ensures that the CheckboxList field is submitted as an array of IDs.
• Laravel allows the exists:regions,id rule to be applied directly to an array without requiring regions.*.
• That’s why the validation works without regions.*, as long as Filament handles the data correctly.

@RemiM With this

Forms\Components\CheckboxList::make('regions')
    ->label(__('Regions'))
    ->relationship(
        titleAttribute: 'name,
        modifyQueryUsing: fn (Builder $query) => $query->orderBy('id'),
    )
    ->required()
    ->rules([
        'array',
        'distinct',
        'exists:regions,id',
    ]),

All Tests passed, only the distinct test fails

✅
test('form validation regions field is required', function () {
    // ...
    
    $component->call('create');

    $component->assertHasFormErrors(['regions' => 'required']);
});

✅
test('form validation regions field is array', function () {
    // ...

    $component
        ->fillForm([
            'regions' => 9999,
        ])
        ->call('create');

    $component->assertHasFormErrors(['regions' => 'array']);
});

❌
test('form validation regions field values is distinct', function () {
    // ...

    $component
        ->fillForm([
            'regions' => [9999, 9999],
        ])
        ->call('create');

    dd($component->get('data.regions'));
    // array:2 [
    //     0 => 9999
    //     1 => 9999
    // ]

    dd($component->errors());
    // As you can see, no distinct error here

    // Illuminate\Support\MessageBag^ {#11174
    //     #messages: array:1 [
    //       "data.regions" => array:1 [
    //         0 => "The selected regions is invalid."
    //       ]
    //     ]
    //     #format: ":message"
    // }

    $component->assertHasFormErrors(['regions' => 'distinct']);
});

✅
test('form validation regions field values must exists in regions table id column', function () {
    $regions = Region::factory()->count(2)->create();

    $ids = $regions->modelKeys();

    // ...

    $component
        ->fillForm([
            'regions' => $ids,
        ])
        ->call('create')
        ->assertHasNoFormErrors(['regions' => 'exists']);

    $lastId = end($ids);

    $component
        ->fillForm([
            'regions' => [$lastId + 1],
        ])
        ->call('create')
        ->assertHasFormErrors(['regions' => 'exists']);
});

so it means the distinct rule is no effect, i guess Filament filtered the array before insert data to database