search value object in keys instead of values

In the choices array, keys are values, whereas values are labels.
When the property chosen to generate choice list labels is not unique across entities, there should be one choice per entity anyway, and not one choice per label.

Form/ChoiceList/ModelChoiceLoader.php

@@ -102,7 +102,7 @@ class ModelChoiceLoader implements ChoiceLoaderInterface
 
                 $id = implode('~', $this->getIdentifierValues($entity));
 
-                if (!array_keys($choices, $valueObject)) {
+                if (!array_key_exists($valueObject, $choices)) {
                     $choices[$valueObject] = array();
                 }
 

Tests/Form/ChoiceList/ModelChoiceLoaderTest.php

@@ -0,0 +1,63 @@
+<?php
+
+/*
+ * This file is part of the Sonata Project package.
+ *
+ * (c) Thomas Rabaix <thomas.rabaix@sonata-project.org>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Sonata\AdminBundle\Tests\Form\ChoiceList;
+
+use Sonata\AdminBundle\Form\ChoiceList\ModelChoiceLoader;
+use Sonata\CoreBundle\Tests\Fixtures\Bundle\Entity\Foo;
+
+class ModelChoiceLoaderTest extends \PHPUnit_Framework_TestCase
+{
+    private $modelManager = null;
+
+    public function setUp()
+    {
+        if (false === interface_exists('Symfony\Component\Form\ChoiceList\Loader\ChoiceLoaderInterface')) {
+            $this->markTestSkipped('Test only available for > SF2.7');
+        }
+
+        $this->modelManager = $this->getMock('Sonata\AdminBundle\Model\ModelManagerInterface');
+    }
+
+    public function testLoadFromEntityWithSamePropertyValues()
+    {
+        $fooA = new Foo();
+        $fooA->setBar(1);
+        $fooA->setBaz('baz');
+
+        $fooB = new Foo();
+        $fooB->setBar(2);
+        $fooB->setBaz('baz');
+
+        $this->modelManager->expects($this->once())
+            ->method('findBy')
+            ->will($this->returnValue(array($fooA, $fooB)));
+
+        $this->modelManager->expects($this->any())
+            ->method('getIdentifierValues')
+            ->will($this->returnCallback(function (Foo $foo) {
+                return array($foo->getBar());
+            }));
+
+        $modelChoiceLoader = new ModelChoiceLoader(
+            $this->modelManager,
+            'Sonata\AdminBundle\Tests\Fixtures\Entity\Foo',
+            'baz'
+        );
+
+        $expectedChoices = array(
+            1 => 'baz (id: 1)',
+            2 => 'baz (id: 2)',
+        );
+
+        $this->assertSame($expectedChoices, $modelChoiceLoader->loadChoiceList()->getOriginalKeys());
+    }
+}