feature #26997 [PropertyInfo] Add an extractor to guess if a property…

… is initializable (dunglas)

This PR was squashed before being merged into the 4.2-dev branch (closes #26997).

Discussion
----------

[PropertyInfo] Add an extractor to guess if a property is initializable

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | n/a   <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | todo

When dealing with value objects, being able to detect if a property can be initialized using the constructor is a very valuable information. It's mandatory to add a proper value object support in API Platform and in the Serializer component.

See api-platform/core#1749 and api-platform/core#1843 for the related discussions, extended use cases and proof of concepts.

This PR adds a new interface to guess if a property can be initialized through the constructor, and an implementation using the reflection (in `ReflectionExtractor`).

Commits
-------

9d2ab9e [PropertyInfo] Add an extractor to guess if a property is initializable

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php

@@ -76,6 +76,7 @@
 use Symfony\Component\PropertyAccess\PropertyAccessor;
 use Symfony\Component\PropertyInfo\PropertyAccessExtractorInterface;
 use Symfony\Component\PropertyInfo\PropertyDescriptionExtractorInterface;
+use Symfony\Component\PropertyInfo\PropertyInitializableExtractorInterface;
 use Symfony\Component\PropertyInfo\PropertyListExtractorInterface;
 use Symfony\Component\PropertyInfo\PropertyTypeExtractorInterface;
 use Symfony\Component\Routing\Loader\AnnotationDirectoryLoader;
@@ -347,6 +348,8 @@ public function load(array $configs, ContainerBuilder $container)
             ->addTag('property_info.description_extractor');
         $container->registerForAutoconfiguration(PropertyAccessExtractorInterface::class)
             ->addTag('property_info.access_extractor');
+        $container->registerForAutoconfiguration(PropertyInitializableExtractorInterface::class)
+            ->addTag('property_info.initializable_extractor');
         $container->registerForAutoconfiguration(EncoderInterface::class)
             ->addTag('serializer.encoder');
         $container->registerForAutoconfiguration(DecoderInterface::class)

src/Symfony/Bundle/FrameworkBundle/Resources/config/property_info.xml

@@ -12,18 +12,21 @@
             <argument type="collection" />
             <argument type="collection" />
             <argument type="collection" />
+            <argument type="collection" />
         </service>
         <service id="Symfony\Component\PropertyInfo\PropertyAccessExtractorInterface" alias="property_info" />
         <service id="Symfony\Component\PropertyInfo\PropertyDescriptionExtractorInterface" alias="property_info" />
         <service id="Symfony\Component\PropertyInfo\PropertyInfoExtractorInterface" alias="property_info" />
         <service id="Symfony\Component\PropertyInfo\PropertyTypeExtractorInterface" alias="property_info" />
         <service id="Symfony\Component\PropertyInfo\PropertyListExtractorInterface" alias="property_info" />
+        <service id="Symfony\Component\PropertyInfo\PropertyInitializableExtractorInterface" alias="property_info" />
 
         <!-- Extractor -->
         <service id="property_info.reflection_extractor" class="Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor">
             <tag name="property_info.list_extractor" priority="-1000" />
             <tag name="property_info.type_extractor" priority="-1002" />
             <tag name="property_info.access_extractor" priority="-1000" />
+            <tag name="property_info.initializable_extractor" priority="-1000" />
         </service>
     </services>
 </container>

src/Symfony/Component/PropertyInfo/CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+4.2.0
+-----
+
+* added `PropertyInitializableExtractorInterface` to test if a property can be initialized through the constructor (implemented by `ReflectionExtractor`)
+
 3.3.0
 -----
 

src/Symfony/Component/PropertyInfo/DependencyInjection/PropertyInfoPass.php

@@ -30,14 +30,16 @@ class PropertyInfoPass implements CompilerPassInterface
     private $typeExtractorTag;
     private $descriptionExtractorTag;
     private $accessExtractorTag;
+    private $initializableExtractorTag;
 
-    public function __construct(string $propertyInfoService = 'property_info', string $listExtractorTag = 'property_info.list_extractor', string $typeExtractorTag = 'property_info.type_extractor', string $descriptionExtractorTag = 'property_info.description_extractor', string $accessExtractorTag = 'property_info.access_extractor')
+    public function __construct(string $propertyInfoService = 'property_info', string $listExtractorTag = 'property_info.list_extractor', string $typeExtractorTag = 'property_info.type_extractor', string $descriptionExtractorTag = 'property_info.description_extractor', string $accessExtractorTag = 'property_info.access_extractor', string $initializableExtractorTag = 'property_info.initializable_extractor')
     {
         $this->propertyInfoService = $propertyInfoService;
         $this->listExtractorTag = $listExtractorTag;
         $this->typeExtractorTag = $typeExtractorTag;
         $this->descriptionExtractorTag = $descriptionExtractorTag;
         $this->accessExtractorTag = $accessExtractorTag;
+        $this->initializableExtractorTag = $initializableExtractorTag;
     }
 
     /**
@@ -62,5 +64,8 @@ public function process(ContainerBuilder $container)
 
         $accessExtractors = $this->findAndSortTaggedServices($this->accessExtractorTag, $container);
         $definition->replaceArgument(3, new IteratorArgument($accessExtractors));
+
+        $initializableExtractors = $this->findAndSortTaggedServices($this->initializableExtractorTag, $container);
+        $definition->replaceArgument(4, new IteratorArgument($initializableExtractors));
     }
 }

src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php

@@ -13,6 +13,7 @@
 
 use Symfony\Component\Inflector\Inflector;
 use Symfony\Component\PropertyInfo\PropertyAccessExtractorInterface;
+use Symfony\Component\PropertyInfo\PropertyInitializableExtractorInterface;
 use Symfony\Component\PropertyInfo\PropertyListExtractorInterface;
 use Symfony\Component\PropertyInfo\PropertyTypeExtractorInterface;
 use Symfony\Component\PropertyInfo\Type;
@@ -24,7 +25,7 @@
  *
  * @final
  */
-class ReflectionExtractor implements PropertyListExtractorInterface, PropertyTypeExtractorInterface, PropertyAccessExtractorInterface
+class ReflectionExtractor implements PropertyListExtractorInterface, PropertyTypeExtractorInterface, PropertyAccessExtractorInterface, PropertyInitializableExtractorInterface
 {
     /**
      * @internal
@@ -146,6 +147,34 @@ public function isWritable($class, $property, array $context = array())
         return null !== $reflectionMethod;
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function isInitializable(string $class, string $property, array $context = array()): ?bool
+    {
+        try {
+            $reflectionClass = new \ReflectionClass($class);
+        } catch (\ReflectionException $e) {
+            return null;
+        }
+
+        if (!$reflectionClass->isInstantiable()) {
+            return false;
+        }
+
+        if ($constructor = $reflectionClass->getConstructor()) {
+            foreach ($constructor->getParameters() as $parameter) {
+                if ($property === $parameter->name) {
+                    return true;
+                }
+            }
+        } elseif ($parentClass = $reflectionClass->getParentClass()) {
+            return $this->isInitializable($parentClass->getName(), $property);
+        }
+
+        return false;
+    }
+
     /**
      * @return Type[]|null
      */

src/Symfony/Component/PropertyInfo/PropertyInfoCacheExtractor.php

@@ -20,7 +20,7 @@
  *
  * @final
  */
-class PropertyInfoCacheExtractor implements PropertyInfoExtractorInterface
+class PropertyInfoCacheExtractor implements PropertyInfoExtractorInterface, PropertyInitializableExtractorInterface
 {
     private $propertyInfoExtractor;
     private $cacheItemPool;
@@ -80,6 +80,14 @@ public function getTypes($class, $property, array $context = array())
         return $this->extract('getTypes', array($class, $property, $context));
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function isInitializable(string $class, string $property, array $context = array()): ?bool
+    {
+        return $this->extract('isInitializable', array($class, $property, $context));
+    }
+
     /**
      * Retrieves the cached data if applicable or delegates to the decorated extractor.
      *

src/Symfony/Component/PropertyInfo/PropertyInfoExtractor.php

@@ -18,25 +18,28 @@
  *
  * @final
  */
-class PropertyInfoExtractor implements PropertyInfoExtractorInterface
+class PropertyInfoExtractor implements PropertyInfoExtractorInterface, PropertyInitializableExtractorInterface
 {
     private $listExtractors;
     private $typeExtractors;
     private $descriptionExtractors;
     private $accessExtractors;
+    private $initializableExtractors;
 
     /**
-     * @param iterable|PropertyListExtractorInterface[]        $listExtractors
-     * @param iterable|PropertyTypeExtractorInterface[]        $typeExtractors
-     * @param iterable|PropertyDescriptionExtractorInterface[] $descriptionExtractors
-     * @param iterable|PropertyAccessExtractorInterface[]      $accessExtractors
+     * @param iterable|PropertyListExtractorInterface[]          $listExtractors
+     * @param iterable|PropertyTypeExtractorInterface[]          $typeExtractors
+     * @param iterable|PropertyDescriptionExtractorInterface[]   $descriptionExtractors
+     * @param iterable|PropertyAccessExtractorInterface[]        $accessExtractors
+     * @param iterable|PropertyInitializableExtractorInterface[] $initializableExtractors
      */
-    public function __construct(iterable $listExtractors = array(), iterable $typeExtractors = array(), iterable $descriptionExtractors = array(), iterable $accessExtractors = array())
+    public function __construct(iterable $listExtractors = array(), iterable $typeExtractors = array(), iterable $descriptionExtractors = array(), iterable $accessExtractors = array(), iterable $initializableExtractors = array())
     {
         $this->listExtractors = $listExtractors;
         $this->typeExtractors = $typeExtractors;
         $this->descriptionExtractors = $descriptionExtractors;
         $this->accessExtractors = $accessExtractors;
+        $this->initializableExtractors = $initializableExtractors;
     }
 
     /**
@@ -87,6 +90,14 @@ public function isWritable($class, $property, array $context = array())
         return $this->extract($this->accessExtractors, 'isWritable', array($class, $property, $context));
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function isInitializable(string $class, string $property, array $context = array()): ?bool
+    {
+        return $this->extract($this->initializableExtractors, 'isInitializable', array($class, $property, $context));
+    }
+
     /**
      * Iterates over registered extractors and return the first value found.
      *

src/Symfony/Component/PropertyInfo/PropertyInitializableExtractorInterface.php

@@ -0,0 +1,25 @@
+<?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\PropertyInfo;
+
+/**
+ * Guesses if the property can be initialized through the constructor.
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+interface PropertyInitializableExtractorInterface
+{
+    /**
+     * Is the property initializable? Returns true if a constructor's parameter matches the given property name.
+     */
+    public function isInitializable(string $class, string $property, array $context = array()): ?bool;
+}

src/Symfony/Component/PropertyInfo/Tests/AbstractPropertyInfoExtractorTest.php

@@ -13,6 +13,7 @@
 
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\PropertyInfo\PropertyInfoExtractor;
+use Symfony\Component\PropertyInfo\PropertyInitializableExtractorInterface;
 use Symfony\Component\PropertyInfo\Tests\Fixtures\DummyExtractor;
 use Symfony\Component\PropertyInfo\Tests\Fixtures\NullExtractor;
 use Symfony\Component\PropertyInfo\Type;
@@ -30,7 +31,7 @@ class AbstractPropertyInfoExtractorTest extends TestCase
     protected function setUp()
     {
         $extractors = array(new NullExtractor(), new DummyExtractor());
-        $this->propertyInfo = new PropertyInfoExtractor($extractors, $extractors, $extractors, $extractors);
+        $this->propertyInfo = new PropertyInfoExtractor($extractors, $extractors, $extractors, $extractors, $extractors);
     }
 
     public function testInstanceOf()
@@ -39,6 +40,7 @@ public function testInstanceOf()
         $this->assertInstanceOf('Symfony\Component\PropertyInfo\PropertyTypeExtractorInterface', $this->propertyInfo);
         $this->assertInstanceOf('Symfony\Component\PropertyInfo\PropertyDescriptionExtractorInterface', $this->propertyInfo);
         $this->assertInstanceOf('Symfony\Component\PropertyInfo\PropertyAccessExtractorInterface', $this->propertyInfo);
+        $this->assertInstanceOf(PropertyInitializableExtractorInterface::class, $this->propertyInfo);
     }
 
     public function testGetShortDescription()
@@ -70,4 +72,9 @@ public function testGetProperties()
     {
         $this->assertEquals(array('a', 'b'), $this->propertyInfo->getProperties('Foo'));
     }
+
+    public function testIsInitializable()
+    {
+        $this->assertTrue($this->propertyInfo->isInitializable('Foo', 'bar', array()));
+    }
 }

src/Symfony/Component/PropertyInfo/Tests/DependencyInjection/PropertyInfoPassTest.php

@@ -26,7 +26,7 @@ public function testServicesAreOrderedAccordingToPriority($index, $tag)
     {
         $container = new ContainerBuilder();
 
-        $definition = $container->register('property_info')->setArguments(array(null, null, null, null));
+        $definition = $container->register('property_info')->setArguments(array(null, null, null, null, null));
         $container->register('n2')->addTag($tag, array('priority' => 100));
         $container->register('n1')->addTag($tag, array('priority' => 200));
         $container->register('n3')->addTag($tag);
@@ -49,14 +49,15 @@ public function provideTags()
             array(1, 'property_info.type_extractor'),
             array(2, 'property_info.description_extractor'),
             array(3, 'property_info.access_extractor'),
+            array(4, 'property_info.initializable_extractor'),
         );
     }
 
     public function testReturningEmptyArrayWhenNoService()
     {
         $container = new ContainerBuilder();
         $propertyInfoExtractorDefinition = $container->register('property_info')
-            ->setArguments(array(array(), array(), array(), array()));
+            ->setArguments(array(array(), array(), array(), array(), array()));
 
         $propertyInfoPass = new PropertyInfoPass();
         $propertyInfoPass->process($container);
@@ -65,5 +66,6 @@ public function testReturningEmptyArrayWhenNoService()
         $this->assertEquals(new IteratorArgument(array()), $propertyInfoExtractorDefinition->getArgument(1));
         $this->assertEquals(new IteratorArgument(array()), $propertyInfoExtractorDefinition->getArgument(2));
         $this->assertEquals(new IteratorArgument(array()), $propertyInfoExtractorDefinition->getArgument(3));
+        $this->assertEquals(new IteratorArgument(array()), $propertyInfoExtractorDefinition->getArgument(4));
     }
 }

src/Symfony/Component/PropertyInfo/Tests/Extractor/ReflectionExtractorTest.php

@@ -14,6 +14,9 @@
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor;
 use Symfony\Component\PropertyInfo\Tests\Fixtures\AdderRemoverDummy;
+use Symfony\Component\PropertyInfo\Tests\Fixtures\NotInstantiable;
+use Symfony\Component\PropertyInfo\Tests\Fixtures\Php71Dummy;
+use Symfony\Component\PropertyInfo\Tests\Fixtures\Php71DummyExtended2;
 use Symfony\Component\PropertyInfo\Type;
 
 /**
@@ -270,4 +273,24 @@ public function testSingularize()
         $this->assertTrue($this->extractor->isWritable(AdderRemoverDummy::class, 'feet'));
         $this->assertEquals(array('analyses', 'feet'), $this->extractor->getProperties(AdderRemoverDummy::class));
     }
+
+    /**
+     * @dataProvider getInitializableProperties
+     */
+    public function testIsInitializable(string $class, string $property, bool $expected)
+    {
+        $this->assertSame($expected, $this->extractor->isInitializable($class, $property));
+    }
+
+    public function getInitializableProperties(): array
+    {
+        return array(
+            array(Php71Dummy::class, 'string', true),
+            array(Php71Dummy::class, 'intPrivate', true),
+            array(Php71Dummy::class, 'notExist', false),
+            array(Php71DummyExtended2::class, 'intWithAccessor', true),
+            array(Php71DummyExtended2::class, 'intPrivate', false),
+            array(NotInstantiable::class, 'foo', false),
+        );
+    }
 }

src/Symfony/Component/PropertyInfo/Tests/Fixtures/DummyExtractor.php

@@ -13,14 +13,15 @@
 
 use Symfony\Component\PropertyInfo\PropertyAccessExtractorInterface;
 use Symfony\Component\PropertyInfo\PropertyDescriptionExtractorInterface;
+use Symfony\Component\PropertyInfo\PropertyInitializableExtractorInterface;
 use Symfony\Component\PropertyInfo\PropertyListExtractorInterface;
 use Symfony\Component\PropertyInfo\PropertyTypeExtractorInterface;
 use Symfony\Component\PropertyInfo\Type;
 
 /**
  * @author Kévin Dunglas <dunglas@gmail.com>
  */
-class DummyExtractor implements PropertyListExtractorInterface, PropertyDescriptionExtractorInterface, PropertyTypeExtractorInterface, PropertyAccessExtractorInterface
+class DummyExtractor implements PropertyListExtractorInterface, PropertyDescriptionExtractorInterface, PropertyTypeExtractorInterface, PropertyAccessExtractorInterface, PropertyInitializableExtractorInterface
 {
     /**
      * {@inheritdoc}
@@ -69,4 +70,12 @@ public function getProperties($class, array $context = array())
     {
         return array('a', 'b');
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isInitializable(string $class, string $property, array $context = array()): ?bool
+    {
+        return true;
+    }
 }

src/Symfony/Component/PropertyInfo/Tests/Fixtures/NotInstantiable.php

@@ -0,0 +1,22 @@
+<?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\PropertyInfo\Tests\Fixtures;
+
+/**
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class NotInstantiable
+{
+    private function __construct(string $foo)
+    {
+    }
+}