[Validator] Allow objects implementing __toString() to be used as violation messages

[Validator] updated changelog

[Validator] updated typehint for ConstraintViolationInterface::getMessage()

[Validator] fixed spacing issue inadvertantly added in previous commit

[Validator] fixed coding standard issues

[Validator] Address feedback

[Validator] Fix coding standard violation

[Validator] update tests

[Validator] Address feedback, Round 2

[Validator] Document ConstraintViolationBuilder::__construct()  parameter

[Validator] Update changelog

[Validator] Adjust parameter documentation order

src/Symfony/Component/Validator/CHANGELOG.md

@@ -20,6 +20,7 @@ CHANGELOG
    `maxPropertyPath` options
  * added a new `notInRangeMessage` option to the `Range` constraint that will
    be used in the violation builder when both `min` and `max` are not null
+ * added ability to use stringable objects as violation messages
 
 4.3.0
 -----

src/Symfony/Component/Validator/ConstraintViolation.php

@@ -32,7 +32,7 @@ class ConstraintViolation implements ConstraintViolationInterface
     /**
      * Creates a new constraint violation.
      *
-     * @param string      $message         The violation message
+     * @param string      $message         The violation message as a string or a stringable object
      * @param string      $messageTemplate The raw violation message
      * @param array       $parameters      The parameters to substitute in the
      *                                     raw violation message
@@ -47,7 +47,7 @@ class ConstraintViolation implements ConstraintViolationInterface
      * @param string|null $code            The error code of the violation
      * @param mixed       $cause           The cause of the violation
      */
-    public function __construct(?string $message, ?string $messageTemplate, array $parameters, $root, ?string $propertyPath, $invalidValue, int $plural = null, $code = null, Constraint $constraint = null, $cause = null)
+    public function __construct($message, ?string $messageTemplate, array $parameters, $root, ?string $propertyPath, $invalidValue, int $plural = null, $code = null, Constraint $constraint = null, $cause = null)
     {
         if (null === $message) {
             @trigger_error(sprintf('Passing a null message when instantiating a "%s" is deprecated since Symfony 4.4.', __CLASS__), E_USER_DEPRECATED);
@@ -58,6 +58,10 @@ class ConstraintViolation implements ConstraintViolationInterface
             @trigger_error(sprintf('Not using a string as the error code in %s() is deprecated since Symfony 4.4. A type-hint will be added in 5.0.', __METHOD__), E_USER_DEPRECATED);
         }
 
+        if (!\is_string($message) && !(\is_object($message) && method_exists($message, '__toString'))) {
+            throw new \TypeError('Constraint violation message should be a string or an object which implements the __toString() method.');
+        }
+
         $this->message = $message;
         $this->messageTemplate = $messageTemplate;
         $this->parameters = $parameters;

src/Symfony/Component/Validator/ConstraintViolationInterface.php

@@ -36,7 +36,7 @@ interface ConstraintViolationInterface
     /**
      * Returns the violation message.
      *
-     * @return string The violation message
+     * @return string The violation message as a string or a stringable object
      */
     public function getMessage();
 

src/Symfony/Component/Validator/Context/ExecutionContextInterface.php

@@ -64,7 +64,7 @@ interface ExecutionContextInterface
     /**
      * Adds a violation at the current node of the validation graph.
      *
-     * @param string $message The error message
+     * @param string $message The error message as a string or a stringable object
      * @param array  $params  The parameters substituted in the error message
      */
     public function addViolation($message, array $params = []);
@@ -81,7 +81,7 @@ interface ExecutionContextInterface
      *         ->setTranslationDomain('number_validation')
      *         ->addViolation();
      *
-     * @param string $message    The error message
+     * @param string $message    The error message as a string or a stringable object
      * @param array  $parameters The parameters substituted in the error message
      *
      * @return ConstraintViolationBuilderInterface The violation builder

src/Symfony/Component/Validator/Tests/ConstraintViolationTest.php

@@ -13,6 +13,8 @@ namespace Symfony\Component\Validator\Tests;
 
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Validator\ConstraintViolation;
+use Symfony\Component\Validator\Tests\Fixtures\CustomArrayObject;
+use Symfony\Component\Validator\Tests\Fixtures\ToString;
 
 class ConstraintViolationTest extends TestCase
 {
@@ -109,6 +111,52 @@ EOF;
         $this->assertSame($expected, (string) $violation);
     }
 
+    public function testMessageCanBeStringableObject()
+    {
+        $message = new ToString();
+        $violation = new ConstraintViolation(
+            $message,
+            (string) $message,
+            [],
+            'Root',
+            'property.path',
+            null
+        );
+
+        $expected = <<<'EOF'
+Root.property.path:
+    toString
+EOF;
+        $this->assertSame($expected, (string) $violation);
+        $this->assertSame($message, $violation->getMessage());
+    }
+
+    public function testMessageCannotBeArray()
+    {
+        $this->expectException(\TypeError::class);
+        $violation = new ConstraintViolation(
+            ['cannot be an array'],
+            '',
+            [],
+            'Root',
+            'property.path',
+            null
+        );
+    }
+
+    public function testMessageObjectMustBeStringable()
+    {
+        $this->expectException(\TypeError::class);
+        $violation = new ConstraintViolation(
+            new CustomArrayObject(),
+            '',
+            [],
+            'Root',
+            'property.path',
+            null
+        );
+    }
+
     /**
      * @group legacy
      * @expectedDeprecation Not using a string as the error code in Symfony\Component\Validator\ConstraintViolation::__construct() is deprecated since Symfony 4.4. A type-hint will be added in 5.0.

src/Symfony/Component/Validator/Violation/ConstraintViolationBuilder.php

@@ -45,9 +45,10 @@ class ConstraintViolationBuilder implements ConstraintViolationBuilderInterface
     private $cause;
 
     /**
+     * @param string              $message    The error message as a string or a stringable object
      * @param TranslatorInterface $translator
      */
-    public function __construct(ConstraintViolationList $violations, Constraint $constraint, ?string $message, array $parameters, $root, string $propertyPath, $invalidValue, $translator, string $translationDomain = null)
+    public function __construct(ConstraintViolationList $violations, Constraint $constraint, $message, array $parameters, $root, string $propertyPath, $invalidValue, $translator, string $translationDomain = null)
     {
         if (null === $message) {
             @trigger_error(sprintf('Passing a null message when instantiating a "%s" is deprecated since Symfony 4.4.', __CLASS__), E_USER_DEPRECATED);