fix: copy ArrayObject contents through recursiveCopy

ArrayObjectFilter copied each element through the public copy(), whose
first statement resets the object map. That map is what keeps one copy
per source object and what guards against cycles, so an object shared
inside an ArrayObject was duplicated and a graph whose cycle ran through
an ArrayObject recursed until memory ran out.

Reach recursiveCopy() through a bound closure, the way the sibling
SplDoublyLinkedListFilter already does. DeepCopy::copy() is unchanged.

ArrayObjectFilterTest stubbed the copy() call being removed, so it is
rewritten against a real DeepCopy like SplDoublyLinkedListFilterTest,
keeping its flags and iterator-class assertions.

src/DeepCopy/TypeFilter/Spl/ArrayObjectFilter.php

@@ -1,6 +1,7 @@
 <?php
 namespace DeepCopy\TypeFilter\Spl;
 
+use Closure;
 use DeepCopy\DeepCopy;
 use DeepCopy\TypeFilter\TypeFilter;
 
@@ -23,11 +24,32 @@ final class ArrayObjectFilter implements TypeFilter
     public function apply(mixed $arrayObject)
     {
         $clone = clone $arrayObject;
+        $copy = $this->createCopyClosure();
+
         foreach ($arrayObject->getArrayCopy() as $k => $v) {
-            $clone->offsetSet($k, $this->copier->copy($v));
+            $clone->offsetSet($k, $copy($v));
         }
 
         return $clone;
     }
+
+    /**
+     * Copies a single value through the copier's recursive entry point rather than through
+     * {@see DeepCopy::copy()}, which starts a new copy and so resets the map of already copied
+     * objects. Going through `copy()` here would duplicate objects shared inside the ArrayObject
+     * and would never terminate on a graph whose cycle runs through one.
+     *
+     * Same approach as {@see SplDoublyLinkedListFilter}.
+     */
+    private function createCopyClosure(): Closure
+    {
+        $copier = $this->copier;
+
+        $copy = function (mixed $value) use ($copier): mixed {
+            return $copier->recursiveCopy($value);
+        };
+
+        return Closure::bind($copy, null, DeepCopy::class);
+    }
 }
 

tests/DeepCopyTest/DeepCopyTest.php

@@ -247,6 +247,35 @@ class DeepCopyTest extends TestCase
         $this->assertSame($copy->getProp1()->c, $copy->getProp2());
     }
 
+    public function test_it_keeps_reference_of_objects_shared_through_an_array_object()
+    {
+        $shared = new stdClass();
+
+        $object = new stdClass();
+        $object->collection = new ArrayObject(['a' => $shared, 'b' => $shared]);
+        $object->direct = $shared;
+
+        $copy = deep_copy($object);
+
+        $this->assertEqualButNotSame($shared, $copy->collection['a']);
+        $this->assertSame($copy->collection['a'], $copy->collection['b']);
+        $this->assertSame($copy->collection['a'], $copy->direct);
+    }
+
+    public function test_it_can_copy_graphs_whose_circular_reference_runs_through_an_array_object()
+    {
+        $parent = new stdClass();
+        $child = new stdClass();
+
+        $child->parent = $parent;
+        $parent->children = new ArrayObject([$child]);
+
+        $copy = deep_copy($parent);
+
+        $this->assertEqualButNotSame($child, $copy->children[0]);
+        $this->assertSame($copy, $copy->children[0]->parent);
+    }
+
     public function test_it_can_copy_graphs_with_circular_references()
     {
         $a = new stdClass();

tests/DeepCopyTest/TypeFilter/Spl/ArrayObjectFilterTest.php

@@ -6,8 +6,8 @@ use ArrayObject;
 use DeepCopy\DeepCopy;
 use DeepCopy\TypeFilter\Spl\ArrayObjectFilter;
 use PHPUnit\Framework\TestCase;
-use Prophecy\Prophecy\ObjectProphecy;
 use RecursiveArrayIterator;
+use stdClass;
 
 /**
  * @author Dominic Tubach <dominic.tubach@to.com>
@@ -21,28 +21,40 @@ final class ArrayObjectFilterTest extends TestCase
      */
     private $arrayObjectFilter;
 
-    /**
-     * @var DeepCopy|ObjectProphecy
-     */
-    private $copierProphecy;
-
     protected function setUp(): void
     {
-        $this->copierProphecy = $this->prophesize(DeepCopy::class);
-        $this->arrayObjectFilter = new ArrayObjectFilter(
-            $this->copierProphecy->reveal()
-        );
+        $this->arrayObjectFilter = new ArrayObjectFilter(new DeepCopy());
     }
 
     public function test_it_deep_copies_an_array_object(): void
     {
-        $arrayObject = new ArrayObject(['foo' => 'bar'], ArrayObject::ARRAY_AS_PROPS, RecursiveArrayIterator::class);
-        $this->copierProphecy->copy('bar')->willReturn('baz');
+        $foo = new stdClass();
+        $foo->bar = 'baz';
 
-        /** @var \ArrayObject $newArrayObject */
+        $arrayObject = new ArrayObject(
+            ['foo' => $foo],
+            ArrayObject::ARRAY_AS_PROPS,
+            RecursiveArrayIterator::class
+        );
+
+        /** @var ArrayObject $newArrayObject */
         $newArrayObject = $this->arrayObjectFilter->apply($arrayObject);
-        $this->assertSame(['foo' => 'baz'], $newArrayObject->getArrayCopy());
+
+        $this->assertNotSame($foo, $newArrayObject['foo']);
+        $this->assertEquals($foo, $newArrayObject['foo']);
         $this->assertSame(ArrayObject::ARRAY_AS_PROPS, $newArrayObject->getFlags());
         $this->assertSame(RecursiveArrayIterator::class, $newArrayObject->getIteratorClass());
     }
+
+    public function test_it_keeps_objects_shared_inside_the_array_object_shared(): void
+    {
+        $shared = new stdClass();
+        $arrayObject = new ArrayObject(['a' => $shared, 'b' => $shared]);
+
+        /** @var ArrayObject $newArrayObject */
+        $newArrayObject = $this->arrayObjectFilter->apply($arrayObject);
+
+        $this->assertNotSame($shared, $newArrayObject['a']);
+        $this->assertSame($newArrayObject['a'], $newArrayObject['b']);
+    }
 }