From 0de9eca17e4e7bf896f0bbb36f28bf0dc34e3b61 Mon Sep 17 00:00:00 2001
From: Alex Wells <autaut03@gmail.com>
Date: Tue, 31 Oct 2023 01:46:33 +0200
Subject: [PATCH] fix: Serialize empty "map" arrays as objects in JSON

---
 .../Primitive/BuiltIn/ArrayMapper.php           | 17 ++++++++++++++++-
 tests/Integration/JsonSerializationTest.php     |  7 ++++---
 tests/Stubs/ClassStub.php                       |  2 ++
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/GoodPhp/Serialization/TypeAdapter/Primitive/BuiltIn/ArrayMapper.php b/src/GoodPhp/Serialization/TypeAdapter/Primitive/BuiltIn/ArrayMapper.php
index 652751f..44e4773 100644
--- a/src/GoodPhp/Serialization/TypeAdapter/Primitive/BuiltIn/ArrayMapper.php
+++ b/src/GoodPhp/Serialization/TypeAdapter/Primitive/BuiltIn/ArrayMapper.php
@@ -3,6 +3,7 @@
 namespace GoodPhp\Serialization\TypeAdapter\Primitive\BuiltIn;
 
 use Exception;
+use GoodPhp\Reflection\Type\PrimitiveType;
 use GoodPhp\Reflection\Type\Type;
 use GoodPhp\Serialization\Serializer;
 use GoodPhp\Serialization\TypeAdapter\Exception\CollectionItemMappingException;
@@ -21,8 +22,18 @@ final class ArrayMapper
 	 * @return array<mixed>
 	 */
 	#[MapTo(PrimitiveTypeAdapter::class)]
-	public function to(array $value, Type $type, Serializer $serializer): array
+	public function to(array $value, Type $type, Serializer $serializer): array|\stdClass
 	{
+		if ($value === []) {
+			// Make sure that map arrays are serialized as object. To do so, we'll return an stdClass instead of
+			// an array so the upper layer can serialize it as an object, not an empty array.
+			if ($type->arguments[0]->equals(PrimitiveType::string())) {
+				return new \stdClass();
+			}
+
+			return $value;
+		}
+
 		$itemAdapter = $serializer->adapter(PrimitiveTypeAdapter::class, $type->arguments[1]);
 
 		return MultipleMappingException::map(
@@ -45,6 +56,10 @@ public function to(array $value, Type $type, Serializer $serializer): array
 	#[MapFrom(PrimitiveTypeAdapter::class)]
 	public function from(array $value, Type $type, Serializer $serializer): array
 	{
+		if ($value === []) {
+			return $value;
+		}
+
 		$itemAdapter = $serializer->adapter(PrimitiveTypeAdapter::class, $type->arguments[1]);
 
 		return MultipleMappingException::map(
diff --git a/tests/Integration/JsonSerializationTest.php b/tests/Integration/JsonSerializationTest.php
index 67c9bc5..561d3a6 100644
--- a/tests/Integration/JsonSerializationTest.php
+++ b/tests/Integration/JsonSerializationTest.php
@@ -144,9 +144,10 @@ public function serializesProvider(): Generator
 				123,
 				MissingValue::INSTANCE,
 				new NestedStub('flattened'),
-				new CarbonImmutable('2020-01-01 00:00:00')
+				new CarbonImmutable('2020-01-01 00:00:00'),
+				['Some key' => 'Some value']
 			),
-			'{"primitive":1,"nested":{"Field":"something"},"date":"2020-01-01T00:00:00.000000Z","optional":123,"nullable":123,"Field":"flattened","carbonImmutable":"2020-01-01T00:00:00.000000Z"}',
+			'{"primitive":1,"nested":{"Field":"something"},"date":"2020-01-01T00:00:00.000000Z","optional":123,"nullable":123,"Field":"flattened","carbonImmutable":"2020-01-01T00:00:00.000000Z","other":{"Some key":"Some value"}}',
 		];
 
 		yield 'ClassStub with empty optional and null nullable' => [
@@ -166,7 +167,7 @@ public function serializesProvider(): Generator
 				new NestedStub('flattened'),
 				new CarbonImmutable('2020-01-01 00:00:00')
 			),
-			'{"primitive":1,"nested":{"Field":"something"},"date":"2020-01-01T00:00:00.000000Z","nullable":null,"Field":"flattened","carbonImmutable":"2020-01-01T00:00:00.000000Z"}',
+			'{"primitive":1,"nested":{"Field":"something"},"date":"2020-01-01T00:00:00.000000Z","nullable":null,"Field":"flattened","carbonImmutable":"2020-01-01T00:00:00.000000Z","other":{}}',
 		];
 	}
 
diff --git a/tests/Stubs/ClassStub.php b/tests/Stubs/ClassStub.php
index 5bfbcdd..2c2ba32 100644
--- a/tests/Stubs/ClassStub.php
+++ b/tests/Stubs/ClassStub.php
@@ -26,6 +26,8 @@ public function __construct(
 		#[Flatten]
 		public NestedStub            $flattened,
 		public readonly CarbonImmutable $carbonImmutable,
+		/** @var array<string, string> */
+		public readonly array $other = [],
 	)
 	{
 	}