bug symfony#57920 [Form] Fix handling empty data in ValueToDuplicatesTransformer (xabbuh)

This PR was merged into the 5.4 branch.

Discussion
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[Form] Fix handling empty data in ValueToDuplicatesTransformer

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Fix symfony#47013
| License       | MIT

The transformer receives the data of child forms that have already been through the transformation schema. If no custom view transformer was used on that child form the empty would already have been changed to null. Thus, receiving an empty string here means that the child form explicitly asked for it and the value must not be exchanged with null.

Commits
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4ec6c80 fix handling empty data in ValueToDuplicatesTransformer

Author: nicolas-grekas

src/Symfony/Component/Form/Extension/Core/DataTransformer/ValueToDuplicatesTransformer.php

@@ -62,7 +62,7 @@ public function reverseTransform($array)
         $emptyKeys = [];
 
         foreach ($this->keys as $key) {
-            if (isset($array[$key]) && '' !== $array[$key] && false !== $array[$key] && [] !== $array[$key]) {
+            if (isset($array[$key]) && false !== $array[$key] && [] !== $array[$key]) {
                 if ($array[$key] !== $result) {
                     throw new TransformationFailedException('All values in the array should be the same.');
                 }

src/Symfony/Component/Form/Tests/Extension/Core/DataTransformer/ValueToDuplicatesTransformerTest.php

@@ -70,7 +70,7 @@ public function testReverseTransformCompletelyEmpty()
             'c' => '',
         ];
 
-        $this->assertNull($this->transformer->reverseTransform($input));
+        $this->assertSame('', $this->transformer->reverseTransform($input));
     }
 
     public function testReverseTransformCompletelyNull()

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

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Form\Tests\Extension\Core\Type;
 
+use Symfony\Component\Form\Extension\Core\Type\TextType;
 use Symfony\Component\Form\Form;
 use Symfony\Component\Form\Tests\Fixtures\NotMappedType;
 use Symfony\Component\OptionsResolver\Exception\InvalidOptionsException;
@@ -191,6 +192,36 @@ public function testSetOptionsPerChildAndOverwrite()
         $this->assertTrue($form['second']->isRequired());
     }
 
+    /**
+     * @dataProvider emptyDataProvider
+     */
+    public function testSubmitNullForTextTypeWithEmptyDataOptionSetToEmptyString($emptyData, $submittedData, $expected)
+    {
+        $form = $this->factory->create(static::TESTED_TYPE, null, [
+            'type' => TextType::class,
+            'options' => [
+                'empty_data' => $emptyData,
+            ]
+        ]);
+        $form->submit($submittedData);
+
+        $this->assertSame($expected, $form->getData());
+    }
+
+    public static function emptyDataProvider()
+    {
+        yield ['', null, ''];
+        yield ['', ['first' => null, 'second' => null], ''];
+        yield ['', ['first' => '', 'second' => null], ''];
+        yield ['', ['first' => null, 'second' => ''], ''];
+        yield ['', ['first' => '', 'second' => ''], ''];
+        yield [null, null, null];
+        yield [null, ['first' => null, 'second' => null], null];
+        yield [null, ['first' => '', 'second' => null], null];
+        yield [null, ['first' => null, 'second' => ''], null];
+        yield [null, ['first' => '', 'second' => ''], null];
+    }
+
     public function testSubmitUnequal()
     {
         $input = ['first' => 'foo', 'second' => 'bar'];