minor #15798 [2.8][Form] Fix php warning on invalid FormFactory::createBuilder() argument (xelaris)

This PR was merged into the 2.8 branch.

Discussion
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[2.8][Form] Fix php warning on invalid FormFactory::createBuilder() argument

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

Without this check it comes to a `strpos() expects parameter 1 to be string, object given` warning, when passing an invalid argument to `FormFactory::createBuilder()` (e.g. when calling `$this->createForm(new AnEntity());` instead of `$this->createForm(new AnEntityType());` in a controller).

Commits
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b5599a5 [Form] Fix php warning on invalid FormFactory::createBuilder() argument

Author: Tobion

FormFactory.php

@@ -76,9 +76,11 @@ public function createBuilder($type = 'Symfony\Component\Form\Extension\Core\Typ
         } elseif ($type instanceof FormTypeInterface) {
             // BC
             $typeName = $type->getName();
-        } else {
+        } elseif (is_string($type)) {
             // BC
             $typeName = $type;
+        } else {
+            throw new UnexpectedTypeException($type, 'string, Symfony\Component\Form\ResolvedFormTypeInterface or Symfony\Component\Form\FormTypeInterface');
         }
 
         if (null === $name) {

Tests/FormFactoryTest.php

@@ -293,6 +293,15 @@ public function testCreateNamedBuilderThrowsUnderstandableException()
         $this->factory->createNamedBuilder('name', new \stdClass());
     }
 
+    /**
+     * @expectedException        \Symfony\Component\Form\Exception\UnexpectedTypeException
+     * @expectedExceptionMessage Expected argument of type "string, Symfony\Component\Form\ResolvedFormTypeInterface or Symfony\Component\Form\FormTypeInterface", "stdClass" given
+     */
+    public function testCreateThrowsUnderstandableException()
+    {
+        $this->factory->create(new \stdClass());
+    }
+
     public function testCreateUsesTypeNameIfTypeGivenAsString()
     {
         $options = array('a' => '1', 'b' => '2');