From 8f03a7e0cbe1b83434e14d05a3f533e26b7a243f Mon Sep 17 00:00:00 2001
From: Romain Canon <romain.hydrocanon@gmail.com>
Date: Sun, 12 Feb 2023 18:12:06 +0700
Subject: [PATCH] fix: properly handle union of `null` and objects

---
 src/Mapper/Tree/Builder/UnionNodeBuilder.php  |  4 ++
 .../Object/UnionOfObjectsMappingTest.php      | 46 +++++++++++++++----
 2 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/src/Mapper/Tree/Builder/UnionNodeBuilder.php b/src/Mapper/Tree/Builder/UnionNodeBuilder.php
index a36b161f..bf6babda 100644
--- a/src/Mapper/Tree/Builder/UnionNodeBuilder.php
+++ b/src/Mapper/Tree/Builder/UnionNodeBuilder.php
@@ -83,6 +83,10 @@ private function tryToBuildClassNode(UnionType $type, Shell $shell, RootNodeBuil
         $classTypes = [];
 
         foreach ($type->types() as $subType) {
+            if ($subType instanceof NullType) {
+                continue;
+            }
+
             if (! $subType instanceof ClassType) {
                 return null;
             }
diff --git a/tests/Integration/Mapping/Object/UnionOfObjectsMappingTest.php b/tests/Integration/Mapping/Object/UnionOfObjectsMappingTest.php
index 16ef982f..0b53b718 100644
--- a/tests/Integration/Mapping/Object/UnionOfObjectsMappingTest.php
+++ b/tests/Integration/Mapping/Object/UnionOfObjectsMappingTest.php
@@ -19,9 +19,9 @@ public function test_objects_sharing_one_property_are_resolved_correctly(): void
                 ->registerConstructor([SomeFooAndBarObject::class, 'constructorB'])
                 ->mapper()
                 ->map(UnionOfFooAndBarAndFoo::class, [
-                'foo',
-                ['foo' => 'foo', 'bar' => 'bar'],
-            ]);
+                    'foo',
+                    ['foo' => 'foo', 'bar' => 'bar'],
+                ]);
         } catch (MappingError $error) {
             $this->mappingFail($error);
         }
@@ -30,6 +30,27 @@ public function test_objects_sharing_one_property_are_resolved_correctly(): void
         self::assertInstanceOf(SomeFooAndBarObject::class, $result->objects[1]);
     }
 
+    public function test_mapping_to_union_of_null_and_objects_can_infer_object(): void
+    {
+        try {
+            $result = (new MapperBuilder())
+                ->mapper()
+                ->map(
+                    'null|' . SomeObjectWithFooAndBar::class . '|' . SomeObjectWithBazAndFiz::class,
+                    [
+                        'baz' => 'baz',
+                        'fiz' => 'fiz',
+                    ]
+                );
+        } catch (MappingError $error) {
+            $this->mappingFail($error);
+        }
+
+        self::assertInstanceOf(SomeObjectWithBazAndFiz::class, $result);
+        self::assertSame('baz', $result->baz);
+        self::assertSame('fiz', $result->fiz);
+    }
+
     /**
      *
      * @dataProvider mapping_error_when_cannot_resolve_union_data_provider
@@ -63,11 +84,6 @@ public function mapping_error_when_cannot_resolve_union_data_provider(): iterabl
     }
 }
 
-final class NativeUnionOfObjects
-{
-    public SomeFooObject|SomeBarObject $object;
-}
-
 // PHP8.1 Readonly properties
 final class UnionOfFooAndBar
 {
@@ -133,3 +149,17 @@ public static function constructorB(string $foo, string $bar): self
         return new self($foo, $bar, 'default baz');
     }
 }
+
+final class SomeObjectWithFooAndBar
+{
+    public string $foo;
+
+    public string $bar;
+}
+
+final class SomeObjectWithBazAndFiz
+{
+    public string $baz;
+
+    public string $fiz;
+}