[WIP][Form] Improve transformation failure message by providing property path

src/Symfony/Component/Form/Form.php

@@ -1049,13 +1049,23 @@ class Form implements \IteratorAggregate, FormInterface
      *
      * @param mixed $value The value to transform
      *
+     * @throws TransformationFailedException If the value cannot be transformed to "normalized" format
+     *
      * @return mixed
      */
     private function modelToNorm($value)
     {
+        try {
             foreach ($this->config->getModelTransformers() as $transformer) {
                 $value = $transformer->transform($value);
             }
+        } catch (TransformationFailedException $exception) {
+            throw new TransformationFailedException(
+                'Unable to transform value for property path "' . $this->getPropertyPath() . '": ' . $exception->getMessage(),
+                $exception->getCode(),
+                $exception
+            );
+        }
 
         return $value;
     }
@@ -1065,15 +1075,25 @@ class Form implements \IteratorAggregate, FormInterface
      *
      * @param string $value The value to reverse transform
      *
+     * @throws TransformationFailedException If the value cannot be transformed to "model" format
+     *
      * @return mixed
      */
     private function normToModel($value)
     {
+        try {
             $transformers = $this->config->getModelTransformers();
 
             for ($i = count($transformers) - 1; $i >= 0; --$i) {
                 $value = $transformers[$i]->reverseTransform($value);
             }
+        } catch (TransformationFailedException $exception) {
+            throw new TransformationFailedException(
+                'Unable to reverse value for property path "' . $this->getPropertyPath() . '": ' . $exception->getMessage(),
+                $exception->getCode(),
+                $exception
+            );
+        }
 
         return $value;
     }
@@ -1083,6 +1103,8 @@ class Form implements \IteratorAggregate, FormInterface
      *
      * @param mixed $value The value to transform
      *
+     * @throws TransformationFailedException If the value cannot be transformed to "view" format
+     *
      * @return mixed
      */
     private function normToView($value)
@@ -1096,9 +1118,17 @@ class Form implements \IteratorAggregate, FormInterface
             return null === $value || is_scalar($value) ? (string) $value : $value;
         }
 
+        try {
             foreach ($this->config->getViewTransformers() as $transformer) {
                 $value = $transformer->transform($value);
             }
+        } catch (TransformationFailedException $exception) {
+            throw new TransformationFailedException(
+                'Unable to transform value for property path "' . $this->getPropertyPath() . '": ' . $exception->getMessage(),
+                $exception->getCode(),
+                $exception
+            );
+        }
 
         return $value;
     }
@@ -1108,6 +1138,8 @@ class Form implements \IteratorAggregate, FormInterface
      *
      * @param string $value The value to reverse transform
      *
+     * @throws TransformationFailedException If the value cannot be transformed to "normalized" format
+     *
      * @return mixed
      */
     private function viewToNorm($value)
@@ -1118,9 +1150,17 @@ class Form implements \IteratorAggregate, FormInterface
             return '' === $value ? null : $value;
         }
 
+        try {
             for ($i = count($transformers) - 1; $i >= 0; --$i) {
                 $value = $transformers[$i]->reverseTransform($value);
             }
+        } catch (TransformationFailedException $exception) {
+            throw new TransformationFailedException(
+                'Unable to reverse value for property path "' . $this->getPropertyPath() . '": ' . $exception->getMessage(),
+                $exception->getCode(),
+                $exception
+            );
+        }
 
         return $value;
     }

src/Symfony/Component/Form/Tests/Fixtures/FixedDataTransformer.php

@@ -12,7 +12,7 @@
 namespace Symfony\Component\Form\Tests\Fixtures;
 
 use Symfony\Component\Form\DataTransformerInterface;
-use Symfony\Component\Form\Exception\RuntimeException;
+use Symfony\Component\Form\Exception\TransformationFailedException;
 
 class FixedDataTransformer implements DataTransformerInterface
 {
@@ -26,7 +26,7 @@ class FixedDataTransformer implements DataTransformerInterface
     public function transform($value)
     {
         if (!array_key_exists($value, $this->mapping)) {
-            throw new RuntimeException(sprintf('No mapping for value "%s"', $value));
+            throw new TransformationFailedException(sprintf('No mapping for value "%s"', $value));
         }
 
         return $this->mapping[$value];
@@ -37,7 +37,7 @@ class FixedDataTransformer implements DataTransformerInterface
         $result = array_search($value, $this->mapping, true);
 
         if ($result === false) {
-            throw new RuntimeException(sprintf('No reverse mapping for value "%s"', $value));
+            throw new TransformationFailedException(sprintf('No reverse mapping for value "%s"', $value));
         }
 
         return $result;

src/Symfony/Component/Form/Tests/SimpleFormTest.php

@@ -74,6 +74,28 @@ class SimpleFormTest extends AbstractFormTest
         $this->assertSame('bar', $form->getViewData());
     }
 
+    /**
+     * @expectedException        \Symfony\Component\Form\Exception\TransformationFailedException
+     * @expectedExceptionMessage Unable to transform value for property path "name": No mapping for value "arg"
+     */
+    public function testDataTransformationFailure()
+    {
+        $model = new FixedDataTransformer(array(
+            'default' => 'foo',
+        ));
+        $view = new FixedDataTransformer(array(
+            'foo' => 'bar',
+        ));
+
+        $config = new FormConfigBuilder('name', null, $this->dispatcher);
+        $config->addViewTransformer($view);
+        $config->addModelTransformer($model);
+        $config->setData('arg');
+        $form = new Form($config);
+
+        $form->getData();
+    }
+
     // https://github.com/symfony/symfony/commit/d4f4038f6daf7cf88ca7c7ab089473cce5ebf7d8#commitcomment-1632879
     public function testDataIsInitializedFromSubmit()
     {