feature #27580 [Form] Add ability to clear form errors (colinodell)

This PR was squashed before being merged into the 4.2-dev branch (closes #27580).

Discussion
----------

[Form] Add ability to clear form errors

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #14060
| License       | MIT
| Doc PR        | symfony/symfony-docs#9916

This PR adds the ability to manually clear form errors, thus improving the DX issue reported in #14060.

Unlike my original approach in #14233 and #27571 which break BC, this adds a new `ClearableErrorInterface` which `Form` implements.  (`Button` does not implement it because buttons can't have errors.)

Commits
-------

9eb755c [Form] Add ability to clear form errors

src/Symfony/Component/Form/ClearableErrorsInterface.php

@@ -0,0 +1,27 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Form;
+
+/**
+ * A form element whose errors can be cleared.
+ *
+ * @author Colin O'Dell <colinodell@gmail.com>
+ */
+interface ClearableErrorsInterface
+{
+    /**
+     * Removes all the errors of this form.
+     *
+     * @param bool $deep Whether to remove errors from child forms as well
+     */
+    public function clearErrors(bool $deep = false);
+}

src/Symfony/Component/Form/Form.php

@@ -58,7 +58,7 @@
  * @author Fabien Potencier <fabien@symfony.com>
  * @author Bernhard Schussek <bschussek@gmail.com>
  */
-class Form implements \IteratorAggregate, FormInterface
+class Form implements \IteratorAggregate, FormInterface, ClearableErrorsInterface
 {
     /**
      * The form's configuration.
@@ -795,6 +795,27 @@ public function getErrors($deep = false, $flatten = true)
         return new FormErrorIterator($this, $errors);
     }
 
+    /**
+     * {@inheritdoc}
+     *
+     * @return $this
+     */
+    public function clearErrors(bool $deep = false): self
+    {
+        $this->errors = array();
+
+        if ($deep) {
+            // Clear errors from children
+            foreach ($this as $child) {
+                if ($child instanceof ClearableErrorsInterface) {
+                    $child->clearErrors(true);
+                }
+            }
+        }
+
+        return $this;
+    }
+
     /**
      * {@inheritdoc}
      */

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

@@ -879,6 +879,48 @@ public function testGetErrorsDeepRecursive()
         $this->assertSame($nestedError, $nestedErrorsAsArray[0]);
     }
 
+    public function testClearErrors()
+    {
+        $this->form->addError(new FormError('Error 1'));
+        $this->form->addError(new FormError('Error 2'));
+
+        $this->assertCount(2, $this->form->getErrors());
+
+        $this->form->clearErrors();
+
+        $this->assertCount(0, $this->form->getErrors());
+    }
+
+    public function testClearErrorsShallow()
+    {
+        $this->form->addError($error1 = new FormError('Error 1'));
+        $this->form->addError($error2 = new FormError('Error 2'));
+
+        $childForm = $this->getBuilder('Child')->getForm();
+        $childForm->addError(new FormError('Nested Error'));
+        $this->form->add($childForm);
+
+        $this->form->clearErrors(false);
+
+        $this->assertCount(0, $this->form->getErrors(false));
+        $this->assertCount(1, $this->form->getErrors(true));
+    }
+
+    public function testClearErrorsDeep()
+    {
+        $this->form->addError($error1 = new FormError('Error 1'));
+        $this->form->addError($error2 = new FormError('Error 2'));
+
+        $childForm = $this->getBuilder('Child')->getForm();
+        $childForm->addError($nestedError = new FormError('Nested Error'));
+        $this->form->add($childForm);
+
+        $this->form->clearErrors(true);
+
+        $this->assertCount(0, $this->form->getErrors(false));
+        $this->assertCount(0, $this->form->getErrors(true));
+    }
+
     // Basic cases are covered in SimpleFormTest
     public function testCreateViewWithChildren()
     {