[PropertyAccess][DX] Added an UninitializedPropertyException

src/Symfony/Component/PropertyAccess/CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 5.1.0
 -----
 
+* Added an `UninitializedPropertyException`
 * Linking to PropertyInfo extractor to remove a lot of duplicate code
 
 4.4.0

src/Symfony/Component/PropertyAccess/Exception/UninitializedPropertyException.php

@@ -0,0 +1,21 @@
+<?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\PropertyAccess\Exception;
+
+/**
+ * Thrown when a property is not initialized.
+ *
+ * @author Jules Pietri <jules@heahprod.com>
+ */
+class UninitializedPropertyException extends AccessException
+{
+}

src/Symfony/Component/PropertyAccess/PropertyAccessor.php

@@ -22,6 +22,7 @@
 use Symfony\Component\PropertyAccess\Exception\NoSuchIndexException;
 use Symfony\Component\PropertyAccess\Exception\NoSuchPropertyException;
 use Symfony\Component\PropertyAccess\Exception\UnexpectedTypeException;
+use Symfony\Component\PropertyAccess\Exception\UninitializedPropertyException;
 use Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor;
 use Symfony\Component\PropertyInfo\PropertyReadInfo;
 use Symfony\Component\PropertyInfo\PropertyReadInfoExtractorInterface;
@@ -389,14 +390,33 @@ private function readProperty(array $zval, string $property, bool $ignoreInvalid
             $name = $access->getName();
             $type = $access->getType();
 
-            if (PropertyReadInfo::TYPE_METHOD === $type) {
-                $result[self::VALUE] = $object->$name();
-            } elseif (PropertyReadInfo::TYPE_PROPERTY === $type) {
-                $result[self::VALUE] = $object->$name;
+            try {
+                if (PropertyReadInfo::TYPE_METHOD === $type) {
+                    try {
+                        $result[self::VALUE] = $object->$name();
+                    } catch (\TypeError $e) {
+                        if (preg_match((sprintf('/^Return value of %s::%s\(\) must be of the type (\w+), null returned$/', preg_quote(\get_class($object)), $name)), $e->getMessage(), $matches)) {
+                            throw new UninitializedPropertyException(sprintf('The method "%s::%s()" returned "null", but expected type "%3$s". Have you forgotten to initialize a property or to make the return type nullable using "?%3$s" instead?', \get_class($object), $name, $matches[1]), 0, $e);
+                        }
 
-                if (isset($zval[self::REF]) && $access->canBeReference()) {
-                    $result[self::REF] = &$object->$name;
+                        throw $e;
+                    }
+                } elseif (PropertyReadInfo::TYPE_PROPERTY === $type) {
+                    $result[self::VALUE] = $object->$name;
+
+                    if (isset($zval[self::REF]) && $access->canBeReference()) {
+                        $result[self::REF] = &$object->$name;
+                    }
                 }
+            } catch (\Error $e) {
+                // handle uninitialized properties in PHP >= 7.4
+                if (\PHP_VERSION_ID >= 70400 && preg_match('/^Typed property ([\w\\\]+)::\$(\w+) must not be accessed before initialization$/', $e->getMessage(), $matches)) {
+                    $r = new \ReflectionProperty($matches[1], $matches[2]);
+
+                    throw new UninitializedPropertyException(sprintf('The property "%s::$%s" is not readable because it is typed "%3$s". You should either initialize it or make it nullable using "?%3$s" instead.', $r->getDeclaringClass()->getName(), $r->getName(), $r->getType()->getName()), 0, $e);
+                }
+
+                throw $e;
             }
         } elseif ($object instanceof \stdClass && property_exists($object, $property)) {
             $result[self::VALUE] = $object->$property;

src/Symfony/Component/PropertyAccess/Tests/PropertyAccessorTest.php

@@ -14,6 +14,7 @@
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Cache\Adapter\ArrayAdapter;
 use Symfony\Component\PropertyAccess\Exception\NoSuchIndexException;
+use Symfony\Component\PropertyAccess\Exception\UninitializedPropertyException;
 use Symfony\Component\PropertyAccess\PropertyAccess;
 use Symfony\Component\PropertyAccess\PropertyAccessor;
 use Symfony\Component\PropertyAccess\Tests\Fixtures\ReturnTyped;
@@ -28,6 +29,8 @@
 use Symfony\Component\PropertyAccess\Tests\Fixtures\TestSingularAndPluralProps;
 use Symfony\Component\PropertyAccess\Tests\Fixtures\Ticket5775Object;
 use Symfony\Component\PropertyAccess\Tests\Fixtures\TypeHinted;
+use Symfony\Component\PropertyAccess\Tests\Fixtures\UninitializedPrivateProperty;
+use Symfony\Component\PropertyAccess\Tests\Fixtures\UninitializedProperty;
 
 class PropertyAccessorTest extends TestCase
 {
@@ -131,6 +134,25 @@ public function testGetValueThrowsExceptionIfIndexNotFoundAndIndexExceptionsEnab
         $this->propertyAccessor->getValue($objectOrArray, $path);
     }
 
+    /**
+     * @requires PHP 7.4
+     */
+    public function testGetValueThrowsExceptionIfUninitializedProperty()
+    {
+        $this->expectException(UninitializedPropertyException::class);
+        $this->expectExceptionMessage('The property "Symfony\Component\PropertyAccess\Tests\Fixtures\UninitializedProperty::$uninitialized" is not readable because it is typed "string". You should either initialize it or make it nullable using "?string" instead.');
+
+        $this->propertyAccessor->getValue(new UninitializedProperty(), 'uninitialized');
+    }
+
+    public function testGetValueThrowsExceptionIfUninitializedPropertyWithGetter()
+    {
+        $this->expectException(UninitializedPropertyException::class);
+        $this->expectExceptionMessage('The method "Symfony\Component\PropertyAccess\Tests\Fixtures\UninitializedPrivateProperty::getUninitialized()" returned "null", but expected type "array". Have you forgotten to initialize a property or to make the return type nullable using "?array" instead?');
+
+        $this->propertyAccessor->getValue(new UninitializedPrivateProperty(), 'uninitialized');
+    }
+
     public function testGetValueThrowsExceptionIfNotArrayAccess()
     {
         $this->expectException('Symfony\Component\PropertyAccess\Exception\NoSuchIndexException');