bug symfony#17822 [WIP] [2.7] [Form] fix empty_data option in expanded ChoiceType (HeahDude)

This PR was merged into the 2.7 branch.

Discussion
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[WIP] [2.7] [Form] fix `empty_data` option in expanded `ChoiceType`

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#17791
| License       | MIT
| Doc PR        | -

It might happen because in `Form::submit()` the handling of `empty_data` [line 597](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Form/Form.php#L597) comes after each child of a compound field has been submitted [line 549](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Form/Form.php#L549).

So when `ChoiceType` is `expanded`, `compound` option is defaulted to `true` and it passes its empty submitted data to its children before handling its own `empty_data` option.

This PR uses the listener already added in `ChoiceType` only when `expanded` is true to handle `empty_data` at `PRE_SUBMIT` [line 539](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Form/Form.php#L539).

- [ ] Fix FQCN in tests for 2.8
- [ ] Remove `choices_as_values` in tests for 3.0

Commits
-------

d479adf [Form] fix `empty_data` option in expanded `ChoiceType`

Author: fabpot

src/Symfony/Component/Form/Extension/Core/Type/ChoiceType.php

@@ -33,6 +33,7 @@
 use Symfony\Component\Form\Extension\Core\EventListener\MergeCollectionListener;
 use Symfony\Component\Form\Extension\Core\DataTransformer\ChoiceToValueTransformer;
 use Symfony\Component\Form\Extension\Core\DataTransformer\ChoicesToValuesTransformer;
+use Symfony\Component\Form\Util\FormUtil;
 use Symfony\Component\OptionsResolver\Options;
 use Symfony\Component\OptionsResolver\OptionsResolver;
 
@@ -90,6 +91,14 @@ public function buildForm(FormBuilderInterface $builder, array $options)
                 $form = $event->getForm();
                 $data = $event->getData();
 
+                if (null === $data) {
+                    $emptyData = $form->getConfig()->getEmptyData();
+
+                    if (false === FormUtil::isEmpty($emptyData) && array() !== $emptyData) {
+                        $data = is_callable($emptyData) ? call_user_func($emptyData, $form, $data) : $emptyData;
+                    }
+                }
+
                 // Convert the submitted data to a string, if scalar, before
                 // casting it to an array
                 if (!is_array($data)) {

src/Symfony/Component/Form/Tests/Extension/Core/Type/ChoiceTypeTest.php

@@ -672,6 +672,66 @@ public function testSubmitSingleNonExpandedObjectChoices()
         $this->assertTrue($form->isSynchronized());
     }
 
+    public function testSubmitSingleChoiceWithEmptyData()
+    {
+        $form = $this->factory->create('choice', null, array(
+            'multiple' => false,
+            'expanded' => false,
+            'choices' => array('test'),
+            'choices_as_values' => true,
+            'empty_data' => 'test',
+        ));
+
+        $form->submit(null);
+
+        $this->assertSame('test', $form->getData());
+    }
+
+    public function testSubmitMultipleChoiceWithEmptyData()
+    {
+        $form = $this->factory->create('choice', null, array(
+            'multiple' => true,
+            'expanded' => false,
+            'choices' => array('test'),
+            'choices_as_values' => true,
+            'empty_data' => array('test'),
+        ));
+
+        $form->submit(null);
+
+        $this->assertSame(array('test'), $form->getData());
+    }
+
+    public function testSubmitSingleChoiceExpandedWithEmptyData()
+    {
+        $form = $this->factory->create('choice', null, array(
+            'multiple' => false,
+            'expanded' => true,
+            'choices' => array('test'),
+            'choices_as_values' => true,
+            'empty_data' => 'test',
+        ));
+
+        $form->submit(null);
+
+        $this->assertSame('test', $form->getData());
+    }
+
+    public function testSubmitMultipleChoiceExpandedWithEmptyData()
+    {
+        $form = $this->factory->create('choice', null, array(
+            'multiple' => true,
+            'expanded' => true,
+            'choices' => array('test'),
+            'choices_as_values' => true,
+            'empty_data' => array('test'),
+        ));
+
+        $form->submit(null);
+
+        $this->assertSame(array('test'), $form->getData());
+    }
+
     /**
      * @group legacy
      */