EntityType's choice_value is removing duplicate values - forms

Question

Im trying to build a select html element populated with database entities. I need the labels and values in the select element to be drawn from non-default entity values, so I use the 'choice_label' and 'choice_value' options.
The problem is that any entities with duplicate 'choice_value' (territory) values are being removed (replaced?).
Here's my form builder:
$builder->add('country', EntityType::class, array(
'class' => 'AcmeCheckoutBundle:Country',
'label' => 'Country',
'query_builder' => function(EntityRepository $er) {
return $er->createQueryBuilder('c')
->orderBy('c.name', 'ASC');
},
'choice_label' => 'name',
'choice_value' => 'territory'
));
This is what I expect:
<select>
<option value="1">United Kingdom</option>
<option value="2">France</option>
<option value="2">Germany</option>
<option value="3">Brazil</option>
<option value="3">Canada</option>
</select>
This is what I'm getting:
<select>
<option value="1">United Kingdom</option>
<option value="2">Germany</option>
<option value="3">Canada</option>
</select>
If I remove 'choice_value' from the form builder I get all the records but obviously with the wrong values.

Answer 1

Prior symfony3 array of choices for ChoiceType has folowing structure:
$choices = [
'value1' => 'label1',
'value2' => 'label2', ...
];
So when you fill this array with your elements, elements with duplicate values are overwritten. Since symfony2.7 array of choices was reworked, now it has inversed structure:
$choices = [
'label1' => 'value1',
'label2' => 'value2', ...
];
Now you can have duplicate values, but must have unique labels. This structure was introduced in symfony2.7 but is not enabled by default and is used by default in symfony3.
To enable this structure in symfony2.7 you can use option choices_as_values (http://symfony.com/doc/2.7/reference/forms/types/choice.html#choices-as-values).
Actually this option is not mentioned in EntityType symfony documentation, but as EntityType extends ChoiceType it should work. If it is not, you can use ChoiceType instead od EntityType and provide choices manually.