bug #34083 [Form] Keep preferred_choices order for choice groups (vilius-g)

This PR was squashed before being merged into the 4.3 branch.

Discussion
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[Form] Keep preferred_choices order for choice groups

| Q             | A
| ------------- | ---
| Branch?       | 4.3
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

Since 4.3 ordering of `preferred_choices` is preserved when displaying form. But this only works for flat options. When the choices are grouped, the preferred groups are in default order.

Now the preferred choice group order is derived by taking the first matching choice from `preferred_choices` and using its position to sort the groups.

Commits
-------

75404e5287 [Form] Keep preferred_choices order for choice groups

Author: nicolas-grekas

ChoiceList/Factory/DefaultChoiceListFactory.php

@@ -101,6 +101,14 @@ public function createView(ChoiceListInterface $list, $preferredChoices = null,
                     unset($otherViews[$key]);
                 }
             }
+
+            foreach ($preferredViewsOrder as $key => $groupViewsOrder) {
+                if ($groupViewsOrder) {
+                    $preferredViewsOrder[$key] = min($groupViewsOrder);
+                } else {
+                    unset($preferredViewsOrder[$key]);
+                }
+            }
         } else {
             // Otherwise use the original structure of the choices
             self::addChoiceViewsFromStructuredValues(
@@ -245,6 +253,9 @@ private static function addChoiceViewsGroupedByCallable($groupBy, $choice, $valu
                 $preferredViews[$groupLabel] = new ChoiceGroupView($groupLabel);
                 $otherViews[$groupLabel] = new ChoiceGroupView($groupLabel);
             }
+            if (!isset($preferredViewsOrder[$groupLabel])) {
+                $preferredViewsOrder[$groupLabel] = [];
+            }
 
             self::addChoiceView(
                 $choice,
@@ -255,7 +266,7 @@ private static function addChoiceViewsGroupedByCallable($groupBy, $choice, $valu
                 $attr,
                 $isPreferred,
                 $preferredViews[$groupLabel]->choices,
-                $preferredViewsOrder,
+                $preferredViewsOrder[$groupLabel],
                 $otherViews[$groupLabel]->choices
             );
         }

Tests/ChoiceList/Factory/DefaultChoiceListFactoryTest.php

@@ -256,6 +256,37 @@ public function testCreateViewFlatPreferredChoicesSameOrder()
         );
     }
 
+    public function testCreateViewFlatPreferredChoiceGroupsSameOrder()
+    {
+        $view = $this->factory->createView(
+            $this->list,
+            [$this->obj4, $this->obj2, $this->obj1, $this->obj3],
+            null, // label
+            null, // index
+            [$this, 'getGroup']
+        );
+
+        $preferredLabels = array_map(static function (ChoiceGroupView $groupView): array {
+            return array_map(static function (ChoiceView $view): string {
+                return $view->label;
+            }, $groupView->choices);
+        }, $view->preferredChoices);
+
+        $this->assertEquals(
+            [
+                'Group 2' => [
+                    2 => 'C',
+                    3 => 'D',
+                ],
+                'Group 1' => [
+                    0 => 'A',
+                    1 => 'B',
+                ],
+            ],
+            $preferredLabels
+        );
+    }
+
     public function testCreateViewFlatPreferredChoicesEmptyArray()
     {
         $view = $this->factory->createView(