bug #17990 [DoctrineBridge][Form] Fix performance regression in Entit…

…yType (kimlai)

This PR was submitted for the master branch but it was merged into the 2.7 branch instead (closes #17990).

Discussion
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[DoctrineBridge][Form] Fix performance regression in EntityType

| Q             | A
| ------------- | ---
| Branch        | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

A performance regression was introduced in 2336d5c

Before, the default behaviour of the `DoctrineLoader` was to only fetch the entities selected in the submitted form.

After, the optimization was only performed when the `choice_value` option was set to `null`.
However, the `DoctrineType` sets a non-null default value to `choice_value`, which means that the default behaviour was not using the optimization anymore.

This commit restores the default behaviour (while keeping the previous commit intent).

References:
- https://github.com/symfony/symfony/blob/v2.7.10/src/Symfony/Bridge/Doctrine/Form/ChoiceList/DoctrineChoiceLoader.php#L149
- https://github.com/symfony/symfony/blob/v2.7.10/src/Symfony/Bridge/Doctrine/Form/Type/DoctrineType.php#L216

Commits
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64c80a6 [DoctrineBridge][Form] Fix performance regression in EntityType

src/Symfony/Bridge/Doctrine/Form/ChoiceList/DoctrineChoiceLoader.php

@@ -146,7 +146,9 @@ public function loadChoicesForValues(array $values, $value = null)
 
         // Optimize performance in case we have an object loader and
         // a single-field identifier
-        if (null === $value && !$this->choiceList && $this->objectLoader && $this->idReader->isSingleId()) {
+        $optimize = null === $value || is_array($value) && $value[0] === $this->idReader;
+
+        if ($optimize && !$this->choiceList && $this->objectLoader && $this->idReader->isSingleId()) {
             $unorderedObjects = $this->objectLoader->getEntitiesByIds($this->idReader->getIdField(), $values);
             $objectsById = array();
             $objects = array();

src/Symfony/Bridge/Doctrine/Tests/Form/Type/EntityTypeTest.php

@@ -789,6 +789,30 @@ public function testOverrideChoicesValuesWithCallable()
         $this->assertSame('BooGroup/Bar', $field->getViewData());
     }
 
+    public function testChoicesForValuesOptimization()
+    {
+        $entity1 = new SingleIntIdEntity(1, 'Foo');
+        $entity2 = new SingleIntIdEntity(2, 'Bar');
+
+        $this->persist(array($entity1, $entity2));
+
+        $field = $this->factory->createNamed('name', 'Symfony\Bridge\Doctrine\Form\Type\EntityType', null, array(
+            'em' => 'default',
+            'class' => self::SINGLE_IDENT_CLASS,
+            'choice_label' => 'name',
+        ));
+
+        $this->em->clear();
+
+        $field->submit(1);
+
+        $unitOfWorkIdentityMap = $this->em->getUnitOfWork()->getIdentityMap();
+        $managedEntitiesNames = array_map('strval', $unitOfWorkIdentityMap['Symfony\Bridge\Doctrine\Tests\Fixtures\SingleIntIdEntity']);
+
+        $this->assertContains((string) $entity1, $managedEntitiesNames);
+        $this->assertNotContains((string) $entity2, $managedEntitiesNames);
+    }
+
     public function testGroupByChoices()
     {
         $item1 = new GroupableEntity(1, 'Foo', 'Group1');