Form get errors (#243)

* FormGetErrors provider

* Wip

* Add stub

* Update stub

src/Plugin.php

@@ -15,6 +15,7 @@ use Psalm\SymfonyPsalmPlugin\Handler\DoctrineRepositoryHandler;
 use Psalm\SymfonyPsalmPlugin\Handler\HeaderBagHandler;
 use Psalm\SymfonyPsalmPlugin\Handler\ParameterBagHandler;
 use Psalm\SymfonyPsalmPlugin\Handler\RequiredSetterHandler;
+use Psalm\SymfonyPsalmPlugin\Provider\FormGetErrorsReturnTypeProvider;
 use Psalm\SymfonyPsalmPlugin\Symfony\ContainerMeta;
 use Psalm\SymfonyPsalmPlugin\Twig\AnalyzedTemplatesTainter;
 use Psalm\SymfonyPsalmPlugin\Twig\CachedTemplatesMapping;
@@ -39,6 +40,7 @@ class Plugin implements PluginEntryPointInterface
         require_once __DIR__.'/Handler/ContainerDependencyHandler.php';
         require_once __DIR__.'/Handler/RequiredSetterHandler.php';
         require_once __DIR__.'/Handler/DoctrineQueryBuilderHandler.php';
+        require_once __DIR__.'/Provider/FormGetErrorsReturnTypeProvider.php';
 
         $api->registerHooksFromClass(HeaderBagHandler::class);
         $api->registerHooksFromClass(ConsoleHandler::class);
@@ -99,6 +101,8 @@ class Plugin implements PluginEntryPointInterface
 
             TemplateFileAnalyzer::setTemplateRootPath($twig_root_path);
         }
+
+        $api->registerHooksFromClass(FormGetErrorsReturnTypeProvider::class);
     }
 
     private function addStubs(RegistrationInterface $api, string $path): void

src/Provider/FormGetErrorsReturnTypeProvider.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace Psalm\SymfonyPsalmPlugin\Provider;
+
+use Psalm\Plugin\EventHandler\Event\MethodReturnTypeProviderEvent;
+use Psalm\Type;
+use Psalm\Type\Atomic\TNamedObject;
+use Symfony\Component\Form\FormError;
+use Symfony\Component\Form\FormErrorIterator;
+
+class FormGetErrorsReturnTypeProvider implements \Psalm\Plugin\EventHandler\MethodReturnTypeProviderInterface
+{
+    public static function getClassLikeNames(): array
+    {
+        return ['Symfony\Component\Form\FormInterface'];
+    }
+
+    public static function getMethodReturnType(MethodReturnTypeProviderEvent $event): ?Type\Union
+    {
+        $method_name_lowercase = $event->getMethodNameLowercase();
+        if ('geterrors' !== $method_name_lowercase) {
+            return null;
+        }
+
+        $args = $event->getCallArgs();
+        $source = $event->getSource();
+
+        if (isset($args[0]) && isset($args[1])) {
+            $first_arg_type = $source->getNodeTypeProvider()->getType($args[0]->value);
+            $second_arg_type = $source->getNodeTypeProvider()->getType($args[1]->value);
+
+            if (
+                $first_arg_type
+                && $first_arg_type->isTrue()
+                && $second_arg_type
+                && $second_arg_type->isFalse()
+            ) {
+                return new Type\Union([
+                    new Type\Atomic\TGenericObject(FormErrorIterator::class, [
+                        new Type\Union([
+                            new TNamedObject(FormError::class),
+                            new TNamedObject(FormErrorIterator::class),
+                        ]),
+                    ]),
+                ]);
+            }
+        }
+
+        return new Type\Union([
+            new Type\Atomic\TGenericObject(FormErrorIterator::class, [
+                new Type\Union([new TNamedObject(FormError::class)]),
+            ]),
+        ]);
+    }
+}

src/Stubs/common/Component/Form/FormErrorIterator.stubphp

@@ -0,0 +1,27 @@
+<?php
+
+namespace Symfony\Component\Form;
+
+/**
+ * @template T of FormError|FormErrorIterator
+ * @implements \ArrayAccess<int, T>
+ * @implements \RecursiveIterator<int, T>
+ * @implements \SeekableIterator<int, T>
+ */
+class FormErrorIterator implements \RecursiveIterator, \SeekableIterator, \ArrayAccess, \Countable
+{
+    /**
+     * @param T[]
+     */
+    public function __construct(FormInterface $form, array $errors);
+
+    /** @return T */
+    public function current();
+
+    /**
+     * @param int $position
+     *
+     * @return T
+     */
+    public function offsetGet($position);
+}

tests/acceptance/acceptance/forms/FormGetErrors.feature

@@ -0,0 +1,72 @@
+@symfony-common
+Feature: Form getErrors return type provider
+
+  Background:
+    Given I have Symfony plugin enabled
+  Scenario: getErrors with anything else than (true, false)
+    Given I have the following code
+          """
+      <?php
+
+      use Symfony\Component\Form\FormInterface;
+
+      function foo(FormInterface $form): array
+      {
+          $messages = [];
+
+          foreach ($form->getErrors() as $error1) {
+              $messages[] = $error1->getMessage();
+          }
+
+          foreach ($form->getErrors(true) as $error2) {
+              $messages[] = $error2->getMessage();
+          }
+
+          foreach ($form->getErrors(false) as $error3) {
+              $messages[] = $error3->getMessage();
+          }
+
+          foreach ($form->getErrors(true, true) as $error4) {
+              $messages[] = $error4->getMessage();
+          }
+
+          foreach ($form->getErrors(false, false) as $error5) {
+              $messages[] = $error5->getMessage();
+          }
+
+          foreach ($form->getErrors(false, true) as $error6) {
+              $messages[] = $error6->getMessage();
+          }
+
+          return $messages;
+      }
+      """
+    When I run Psalm
+    Then I see no other errors
+
+  Scenario: getErrors with (true, false)
+    Given I have the following code
+          """
+      <?php
+
+      use Symfony\Component\Form\FormInterface;
+
+      function foo(FormInterface $form): array
+      {
+          $messages = [];
+
+          foreach ($form->getErrors(true, false) as $error7) {
+              /** @psalm-trace $error7 */
+              $messages[] = $error7->getMessage();
+          }
+
+          return $messages;
+      }
+      """
+    When I run Psalm
+    Then I see these errors
+      | Type                    | Message                                                                             |
+      | Trace                   | $error7: Symfony\Component\Form\FormError\|Symfony\Component\Form\FormErrorIterator |
+      | MixedAssignment         | Unable to determine the type of this assignment                                     |
+      | PossiblyUndefinedMethod | Method Symfony\Component\Form\FormErrorIterator::getMessage does not exist          |
+    And I see no other errors