[Serializer] Encode empty objects as objects, not arrays

mcfedr · mcfedr · commit 8bb0b301a635 · 2018-09-04T20:58:08.000+03:00
Allows Normalizers to return a representation of an empty object that the encoder recognizes as such.
diff --git a/src/Symfony/Component/Serializer/Encoder/XmlEncoder.php b/src/Symfony/Component/Serializer/Encoder/XmlEncoder.php
@@ -14,6 +14,7 @@
 use Symfony\Component\Serializer\Exception\NotEncodableValueException;
 use Symfony\Component\Serializer\SerializerAwareInterface;
 use Symfony\Component\Serializer\SerializerAwareTrait;
+use Symfony\Component\Serializer\Util\EmptyObject;
 
 /**
  * Encodes XML data.
@@ -469,6 +470,8 @@ private function selectNodeType(\DOMNode $node, $val): bool
             $node->appendChild($child);
         } elseif ($val instanceof \Traversable) {
             $this->buildXml($node, $val);
+        } elseif ($val instanceof EmptyObject) {
+            // Do nothing
         } elseif (\is_object($val)) {
             return $this->selectNodeType($node, $this->serializer->normalize($val, $this->format, $this->context));
         } elseif (is_numeric($val)) {
diff --git a/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
@@ -24,6 +24,7 @@
 use Symfony\Component\Serializer\Mapping\ClassDiscriminatorResolverInterface;
 use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactoryInterface;
 use Symfony\Component\Serializer\NameConverter\NameConverterInterface;
+use Symfony\Component\Serializer\Util\EmptyObject;
 
 /**
  * Base class for a normalizer dealing with objects.
@@ -119,6 +120,10 @@ public function normalize($object, $format = null, array $context = array())
             $data = $this->updateData($data, $attribute, $this->serializer->normalize($attributeValue, $format, $this->createChildContext($context, $attribute)));
         }
 
+        if (!\count($data)) {
+            return new EmptyObject();
+        }
+
         return $data;
     }
 
diff --git a/src/Symfony/Component/Serializer/Serializer.php b/src/Symfony/Component/Serializer/Serializer.php
@@ -27,6 +27,7 @@
 use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
 use Symfony\Component\Serializer\Normalizer\NormalizerAwareInterface;
 use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
+use Symfony\Component\Serializer\Util\EmptyObject;
 
 /**
  * Serializer serializes and deserializes data.
@@ -138,7 +139,7 @@ public function normalize($data, $format = null, array $context = array())
             return $normalizer->normalize($data, $format, $context);
         }
 
-        if (null === $data || is_scalar($data)) {
+        if (null === $data || is_scalar($data) || $data instanceof EmptyObject) {
             return $data;
         }
 
diff --git a/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractObjectNormalizerTest.php b/src/Symfony/Component/Serializer/Tests/Normalizer/AbstractObjectNormalizerTest.php
@@ -23,6 +23,7 @@
 use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
 use Symfony\Component\Serializer\SerializerAwareInterface;
 use Symfony\Component\Serializer\SerializerInterface;
+use Symfony\Component\Serializer\Util\EmptyObject;
 
 class AbstractObjectNormalizerTest extends TestCase
 {
@@ -161,12 +162,21 @@ public function testExtraAttributesException()
             'allow_extra_attributes' => false,
         ));
     }
+
+    public function testNormalizeEmptyObject()
+    {
+        $normalizer = new AbstractObjectNormalizerDummy();
+        $normalizedData = $normalizer->normalize(new EmptyDummy());
+
+        $this->assertEquals(new EmptyObject(), $normalizedData);
+    }
 }
 
 class AbstractObjectNormalizerDummy extends AbstractObjectNormalizer
 {
     protected function extractAttributes($object, $format = null, array $context = array())
     {
+        return array();
     }
 
     protected function getAttributeValue($object, $attribute, $format = null, array $context = array())
@@ -196,6 +206,10 @@ class Dummy
     public $baz;
 }
 
+class EmptyDummy
+{
+}
+
 class AbstractObjectNormalizerWithMetadata extends AbstractObjectNormalizer
 {
     public function __construct()
diff --git a/src/Symfony/Component/Serializer/Tests/Normalizer/ObjectNormalizerTest.php b/src/Symfony/Component/Serializer/Tests/Normalizer/ObjectNormalizerTest.php
@@ -29,6 +29,7 @@
 use Symfony\Component\Serializer\Tests\Fixtures\GroupDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\MaxDepthDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\SiblingHolder;
+use Symfony\Component\Serializer\Util\EmptyObject;
 
 /**
  * @author Kévin Dunglas <dunglas@gmail.com>
@@ -319,7 +320,7 @@ public function testNormalizeNoPropertyInGroup()
         $obj = new GroupDummy();
         $obj->setFoo('foo');
 
-        $this->assertEquals(array(), $this->normalizer->normalize($obj, null, array('groups' => array('notExist'))));
+        $this->assertEquals(new EmptyObject(), $this->normalizer->normalize($obj, null, array('groups' => array('notExist'))));
     }
 
     public function testGroupsNormalizeWithNameConverter()
diff --git a/src/Symfony/Component/Serializer/Tests/Normalizer/PropertyNormalizerTest.php b/src/Symfony/Component/Serializer/Tests/Normalizer/PropertyNormalizerTest.php
@@ -24,6 +24,7 @@
 use Symfony\Component\Serializer\Tests\Fixtures\MaxDepthDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\PropertyCircularReferenceDummy;
 use Symfony\Component\Serializer\Tests\Fixtures\PropertySiblingHolder;
+use Symfony\Component\Serializer\Util\EmptyObject;
 
 class PropertyNormalizerTest extends TestCase
 {
@@ -154,7 +155,7 @@ public function testIgnoredAttributes()
         $obj->setBar('bar');
 
         $this->assertEquals(
-            array(),
+            new EmptyObject(),
             $this->normalizer->normalize($obj, 'any')
         );
     }
diff --git a/src/Symfony/Component/Serializer/Tests/SerializerTest.php b/src/Symfony/Component/Serializer/Tests/SerializerTest.php
@@ -14,7 +14,10 @@
 use Doctrine\Common\Annotations\AnnotationReader;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor;
+use Symfony\Component\Serializer\Encoder\CsvEncoder;
 use Symfony\Component\Serializer\Encoder\JsonEncoder;
+use Symfony\Component\Serializer\Encoder\XmlEncoder;
+use Symfony\Component\Serializer\Encoder\YamlEncoder;
 use Symfony\Component\Serializer\Mapping\ClassDiscriminatorFromClassMetadata;
 use Symfony\Component\Serializer\Mapping\ClassDiscriminatorMapping;
 use Symfony\Component\Serializer\Mapping\ClassMetadata;
@@ -182,6 +185,48 @@ public function testSerializeArrayOfScalars()
         $this->assertEquals(json_encode($data), $result);
     }
 
+    public function testSerializeEmpty()
+    {
+        $serializer = new Serializer(array(new ObjectNormalizer()), array('json' => new JsonEncoder()));
+        $data = array('foo' => new \stdClass());
+        $result = $serializer->serialize($data, 'json');
+        $this->assertEquals('{"foo":{}}', $result);
+    }
+
+    public function testSerializeEmptyYaml()
+    {
+        $serializer = new Serializer(array(new ObjectNormalizer()), array('yaml' => new YamlEncoder()));
+        $data = array('foo' => new \stdClass());
+        $result = $serializer->serialize($data, 'yaml');
+        $this->assertEquals('{ foo: null }', $result);
+    }
+
+    public function testSerializeEmptyXml()
+    {
+        $serializer = new Serializer(array(new ObjectNormalizer()), array('xml' => new XmlEncoder()));
+        $data = array('foo' => new \stdClass());
+        $result = $serializer->serialize($data, 'xml');
+        $this->assertEquals(<<<'XML'
+<?xml version="1.0"?>
+<response><foo/></response>
+
+XML
+        , $result);
+    }
+
+    public function testSerializeEmptyCsv()
+    {
+        $serializer = new Serializer(array(new ObjectNormalizer()), array('csv' => new CsvEncoder()));
+        $data = array('foo' => new \stdClass(), 'bar' => new \stdClass());
+        $result = $serializer->serialize($data, 'csv');
+        $this->assertEquals(<<<'CSV'
+foo,bar
+,
+
+CSV
+, $result);
+    }
+
     /**
      * @expectedException \Symfony\Component\Serializer\Exception\UnexpectedValueException
      */
diff --git a/src/Symfony/Component/Serializer/Util/EmptyObject.php b/src/Symfony/Component/Serializer/Util/EmptyObject.php
@@ -0,0 +1,31 @@
+<?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\Serializer\Util;
+
+/**
+ * Represents an empty object that has already been normalized
+ * Used to make sure you get {} instead of [] in the output.
+ *
+ * @author Fred Cox <mcfedr@gmail.com>
+ */
+class EmptyObject
+{
+    /**
+     * This value is used by the CsvEncoder.
+     *
+     * @return string
+     */
+    public function __toString()
+    {
+        return '';
+    }
+}

Original file line number	Diff line number	Diff line change
`@@ -27,6 +27,7 @@`
`27`	`27`	`use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;`
`28`	`28`	`use Symfony\Component\Serializer\Normalizer\NormalizerAwareInterface;`
`29`	`29`	`use Symfony\Component\Serializer\Normalizer\NormalizerInterface;`
	`30`	`+use Symfony\Component\Serializer\Util\EmptyObject;`
`30`	`31`
`31`	`32`	`/**`
`32`	`33`	`* Serializer serializes and deserializes data.`
`@@ -138,7 +139,7 @@ public function normalize($data, $format = null, array $context = array())`
`138`	`139`	`return $normalizer->normalize($data, $format, $context);`
`139`	`140`	`}`
`140`	`141`
`141`		`- if (null === $data \|\| is_scalar($data)) {`
	`142`	`+ if (null === $data \|\| is_scalar($data) \|\| $data instanceof EmptyObject) {`
`142`	`143`	`return $data;`
`143`	`144`	`}`
`144`	`145`
Original file line number	Diff line number	Diff line change
`@@ -23,6 +23,7 @@`
`23`	`23`	`use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;`
`24`	`24`	`use Symfony\Component\Serializer\SerializerAwareInterface;`
`25`	`25`	`use Symfony\Component\Serializer\SerializerInterface;`
	`26`	`+use Symfony\Component\Serializer\Util\EmptyObject;`
`26`	`27`
`27`	`28`	`class AbstractObjectNormalizerTest extends TestCase`
`28`	`29`	`{`
`@@ -161,12 +162,21 @@ public function testExtraAttributesException()`
`161`	`162`	`'allow_extra_attributes' => false,`
`162`	`163`	`));`
`163`	`164`	`}`
	`165`	`+`
	`166`	`+ public function testNormalizeEmptyObject()`
	`167`	`+ {`
	`168`	`+ $normalizer = new AbstractObjectNormalizerDummy();`
	`169`	`+ $normalizedData = $normalizer->normalize(new EmptyDummy());`
	`170`	`+`
	`171`	`+ $this->assertEquals(new EmptyObject(), $normalizedData);`
	`172`	`+ }`
`164`	`173`	`}`
`165`	`174`
`166`	`175`	`class AbstractObjectNormalizerDummy extends AbstractObjectNormalizer`
`167`	`176`	`{`
`168`	`177`	`protected function extractAttributes($object, $format = null, array $context = array())`
`169`	`178`	`{`
	`179`	`+ return array();`
`170`	`180`	`}`
`171`	`181`
`172`	`182`	`protected function getAttributeValue($object, $attribute, $format = null, array $context = array())`
`@@ -196,6 +206,10 @@ class Dummy`
`196`	`206`	`public $baz;`
`197`	`207`	`}`
`198`	`208`
	`209`	`+class EmptyDummy`
	`210`	`+{`
	`211`	`+}`
	`212`	`+`
`199`	`213`	`class AbstractObjectNormalizerWithMetadata extends AbstractObjectNormalizer`
`200`	`214`	`{`
`201`	`215`	`public function __construct()`
Original file line number	Diff line number	Diff line change
`@@ -24,6 +24,7 @@`
`24`	`24`	`use Symfony\Component\Serializer\Tests\Fixtures\MaxDepthDummy;`
`25`	`25`	`use Symfony\Component\Serializer\Tests\Fixtures\PropertyCircularReferenceDummy;`
`26`	`26`	`use Symfony\Component\Serializer\Tests\Fixtures\PropertySiblingHolder;`
	`27`	`+use Symfony\Component\Serializer\Util\EmptyObject;`
`27`	`28`
`28`	`29`	`class PropertyNormalizerTest extends TestCase`
`29`	`30`	`{`
`@@ -154,7 +155,7 @@ public function testIgnoredAttributes()`
`154`	`155`	`$obj->setBar('bar');`
`155`	`156`
`156`	`157`	`$this->assertEquals(`
`157`		`- array(),`
	`158`	`+ new EmptyObject(),`
`158`	`159`	`$this->normalizer->normalize($obj, 'any')`
`159`	`160`	`);`
`160`	`161`	`}`