Free memory when a service is no longer used

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Changed
+
+- Unused services are freed from memory
+
 ### Removed
 
 - Using a `string` as a service name

src/Container.php

@@ -10,23 +10,23 @@
 use Innmind\Immutable\{
     Map,
     Sequence,
+    Maybe,
     Str,
 };
 
 final class Container
 {
-    /** @var array<string, object> */
-    private array $services = [];
-
     /**
      * @psalm-mutation-free
      *
      * @param Map<Service, callable(self): object> $definitions
      * @param Sequence<Service> $building
+     * @param Map<Service, \WeakReference<object>> $services
      */
     private function __construct(
         private Map $definitions,
         private Sequence $building,
+        private Map $services,
     ) {
     }
 
@@ -75,7 +75,22 @@ public function __invoke(Service $name): object
              * @psalm-suppress InvalidPropertyAssignmentValue
              * @var T
              */
-            return $this->services[\spl_object_hash($name)] ??= $definition($this);
+            return $this
+                ->services
+                ->get($name)
+                ->flatMap(static fn($service) => Maybe::of($service->get()))
+                ->match(
+                    static fn($service) => $service,
+                    function() use ($name, $definition) {
+                        $service = $definition($this);
+                        $this->services = $this->services->put(
+                            $name,
+                            \WeakReference::create($service),
+                        );
+
+                        return $service;
+                    },
+                );
         } finally {
             $this->building = $this->building->dropEnd(1);
         }
@@ -88,6 +103,10 @@ public function __invoke(Service $name): object
      */
     public static function of(Map $definitions): self
     {
-        return new self($definitions, Sequence::of());
+        return new self(
+            $definitions,
+            Sequence::of(),
+            Map::of(),
+        );
     }
 }

tests/ContainerTest.php

@@ -80,4 +80,20 @@ public function testEnumCaseCanBeUsedToReferenceAService()
 
         $this->assertSame($expected, $container(Services::a));
     }
+
+    public function testServicesAreFreedFromMemoryWhenUnused()
+    {
+        $called = 0;
+        $container = Builder::new()
+            ->add(Services::name, static function() use (&$called) {
+                ++$called;
+
+                return new \stdClass;
+            })
+            ->build();
+
+        $container(Services::name);
+        $this->assertInstanceOf(\stdClass::class, $container(Services::name));
+        $this->assertSame(2, $called);
+    }
 }