bug #15546 [Form] fixed BC-break on grouped choice lists (origaminal)

This PR was squashed before being merged into the 2.7 branch (closes #15546).

Discussion
----------

[Form] fixed BC-break on grouped choice lists

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #15037
| License       | MIT
| Doc PR        |

Commits
-------

12a7dd1 [Form] fixed BC-break on grouped choice lists

Author: fabpot

ChoiceList/Factory/DefaultChoiceListFactory.php

@@ -64,16 +64,18 @@ public function createView(ChoiceListInterface $list, $preferredChoices = null,
         // Backwards compatibility
         if ($list instanceof LegacyChoiceListAdapter && empty($preferredChoices)
             && null === $label && null === $index && null === $groupBy && null === $attr) {
-            $mapToNonLegacyChoiceView = function (LegacyChoiceView $choiceView) {
-                return new ChoiceView($choiceView->data, $choiceView->value, $choiceView->label);
+            $mapToNonLegacyChoiceView = function (LegacyChoiceView &$choiceView) {
+                $choiceView = new ChoiceView($choiceView->data, $choiceView->value, $choiceView->label);
             };
 
             $adaptedList = $list->getAdaptedList();
 
-            return new ChoiceListView(
-                array_map($mapToNonLegacyChoiceView, $adaptedList->getRemainingViews()),
-                array_map($mapToNonLegacyChoiceView, $adaptedList->getPreferredViews())
-            );
+            $remainingViews = $adaptedList->getRemainingViews();
+            $preferredViews = $adaptedList->getPreferredViews();
+            array_walk_recursive($remainingViews, $mapToNonLegacyChoiceView);
+            array_walk_recursive($preferredViews, $mapToNonLegacyChoiceView);
+
+            return new ChoiceListView($remainingViews, $preferredViews);
         }
 
         $preferredViews = array();

Tests/ChoiceList/Factory/DefaultChoiceListFactoryTest.php

@@ -737,7 +737,7 @@ function ($object, $key, $value) {
     /**
      * @group legacy
      */
-    public function testCreateViewForLegacyChoiceList()
+    public function testCreateViewForFlatLegacyChoiceList()
     {
         // legacy ChoiceList instances provide legacy ChoiceView objects
         $preferred = array(new LegacyChoiceView('x', 'x', 'Preferred'));
@@ -758,6 +758,36 @@ public function testCreateViewForLegacyChoiceList()
         $this->assertEquals(array(new ChoiceView('x', 'x', 'Preferred')), $view->preferredChoices);
     }
 
+    /**
+     * @group legacy
+     */
+    public function testCreateViewForNestedLegacyChoiceList()
+    {
+        // legacy ChoiceList instances provide legacy ChoiceView objects
+        $preferred = array('Section 1' => array(new LegacyChoiceView('x', 'x', 'Preferred')));
+        $other = array(
+            'Section 2' => array(new LegacyChoiceView('y', 'y', 'Other')),
+            new LegacyChoiceView('z', 'z', 'Other one'),
+        );
+
+        $list = $this->getMock('Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceListInterface');
+
+        $list->expects($this->once())
+            ->method('getPreferredViews')
+            ->will($this->returnValue($preferred));
+        $list->expects($this->once())
+            ->method('getRemainingViews')
+            ->will($this->returnValue($other));
+
+        $view = $this->factory->createView(new LegacyChoiceListAdapter($list));
+
+        $this->assertEquals(array(
+            'Section 2' => array(new ChoiceView('y', 'y', 'Other')),
+            new ChoiceView('z', 'z', 'Other one'),
+        ), $view->choices);
+        $this->assertEquals(array('Section 1' => array(new ChoiceView('x', 'x', 'Preferred'))), $view->preferredChoices);
+    }
+
     private function assertScalarListWithChoiceValues(ChoiceListInterface $list)
     {
         $this->assertSame(array('a', 'b', 'c', 'd'), $list->getValues());