minor #13515 [Form] fixed form tests when using 2.7 deps (fabpot)

This PR was merged into the 2.6 branch.

Discussion
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[Form] fixed form tests when using 2.7 deps

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

This PR allows tests to pass for the Form subtree-split when using any version of the Validator component. The build was broken because the 2.4 API works in the same way as the 2.5 one in Symfony 2.7, so the cause is set. Testing the implementation of the context allows to know whether to expect the cause more reliably.

Commits
-------

a55f5c8 [Form] fixed form tests when using 2.7 deps

Author: fabpot

Tests/Extension/Validator/Constraints/FormValidatorTest.php

@@ -18,6 +18,7 @@
 use Symfony\Component\Form\Extension\Validator\Constraints\Form;
 use Symfony\Component\Form\Extension\Validator\Constraints\FormValidator;
 use Symfony\Component\Form\SubmitButtonBuilder;
+use Symfony\Component\Validator\Context\ExecutionContextInterface;
 use Symfony\Component\Validator\Constraints\NotNull;
 use Symfony\Component\Validator\Constraints\NotBlank;
 use Symfony\Component\Validator\Tests\Constraints\AbstractConstraintValidatorTest;
@@ -224,14 +225,12 @@ function () { throw new TransformationFailedException(); }
 
         $this->validator->validate($form, new Form());
 
-        $is2Dot4Api = Validation::API_VERSION_2_4 === $this->getApiVersion();
-
         $this->buildViolation('invalid_message_key')
             ->setParameter('{{ value }}', 'foo')
             ->setParameter('{{ foo }}', 'bar')
             ->setInvalidValue('foo')
             ->setCode(Form::NOT_SYNCHRONIZED_ERROR)
-            ->setCause($is2Dot4Api ? null : $form->getTransformationFailure())
+            ->setCause($this->context instanceof ExecutionContextInterface ? $form->getTransformationFailure() : null)
             ->assertRaised();
     }
 
@@ -261,14 +260,12 @@ function () { throw new TransformationFailedException(); }
 
         $this->validator->validate($form, new Form());
 
-        $is2Dot4Api = Validation::API_VERSION_2_4 === $this->getApiVersion();
-
         $this->buildViolation('invalid_message_key')
             ->setParameter('{{ value }}', 'foo')
             ->setParameter('{{ foo }}', 'bar')
             ->setInvalidValue('foo')
             ->setCode(Form::NOT_SYNCHRONIZED_ERROR)
-            ->setCause($is2Dot4Api ? null : $form->getTransformationFailure())
+            ->setCause($this->context instanceof ExecutionContextInterface ? $form->getTransformationFailure() : null)
             ->assertRaised();
     }
 
@@ -298,13 +295,11 @@ function () { throw new TransformationFailedException(); }
 
         $this->validator->validate($form, new Form());
 
-        $is2Dot4Api = Validation::API_VERSION_2_4 === $this->getApiVersion();
-
         $this->buildViolation('invalid_message_key')
             ->setParameter('{{ value }}', 'foo')
             ->setInvalidValue('foo')
             ->setCode(Form::NOT_SYNCHRONIZED_ERROR)
-            ->setCause($is2Dot4Api ? null : $form->getTransformationFailure())
+            ->setCause($this->context instanceof ExecutionContextInterface ? $form->getTransformationFailure() : null)
             ->assertRaised();
     }