Core: fix some memory leak sources without removing caching (#2400)

* Core: fix some memory leak sources

* Core: run gc before detecting memory leaks

* Core: restore caching in BaseClasses.MultiWorld

* SM: move spheres cache to MultiWorld._sm_spheres to avoid memory leak

* Test: add tests for world memory leaks

* Test: limit WorldTestBase leak-check to py>=3.11

---------

Co-authored-by: Fabian Dill <fabian.dill@web.de>

test/bases.py

@@ -1,3 +1,4 @@
+import sys
 import typing
 import unittest
 from argparse import Namespace
@@ -107,11 +108,36 @@ class WorldTestBase(unittest.TestCase):
     game: typing.ClassVar[str]  # define game name in subclass, example "Secret of Evermore"
     auto_construct: typing.ClassVar[bool] = True
     """ automatically set up a world for each test in this class """
+    memory_leak_tested: typing.ClassVar[bool] = False
+    """ remember if memory leak test was already done for this class """
 
     def setUp(self) -> None:
         if self.auto_construct:
             self.world_setup()
 
+    def tearDown(self) -> None:
+        if self.__class__.memory_leak_tested or not self.options or not self.constructed or \
+                sys.version_info < (3, 11, 0):  # the leak check in tearDown fails in py<3.11 for an unknown reason
+            # only run memory leak test once per class, only for constructed with non-default options
+            # default options will be tested in test/general
+            super().tearDown()
+            return
+
+        import gc
+        import weakref
+        weak = weakref.ref(self.multiworld)
+        for attr_name in dir(self):  # delete all direct references to MultiWorld and World
+            attr: object = typing.cast(object, getattr(self, attr_name))
+            if type(attr) is MultiWorld or isinstance(attr, AutoWorld.World):
+                delattr(self, attr_name)
+        state_cache: typing.Optional[typing.Dict[typing.Any, typing.Any]] = getattr(self, "_state_cache", None)
+        if state_cache is not None:  # in case of multiple inheritance with TestBase, we need to clear its cache
+            state_cache.clear()
+        gc.collect()
+        self.__class__.memory_leak_tested = True
+        self.assertFalse(weak(), f"World {getattr(self, 'game', '')} leaked MultiWorld object")
+        super().tearDown()
+
     def world_setup(self, seed: typing.Optional[int] = None) -> None:
         if type(self) is WorldTestBase or \
                 (hasattr(WorldTestBase, self._testMethodName)

test/general/test_memory.py

@@ -0,0 +1,16 @@
+import unittest
+
+from worlds.AutoWorld import AutoWorldRegister
+from . import setup_solo_multiworld
+
+
+class TestWorldMemory(unittest.TestCase):
+    def test_leak(self):
+        """Tests that worlds don't leak references to MultiWorld or themselves with default options."""
+        import gc
+        import weakref
+        for game_name, world_type in AutoWorldRegister.world_types.items():
+            with self.subTest("Game", game_name=game_name):
+                weak = weakref.ref(setup_solo_multiworld(world_type))
+                gc.collect()
+                self.assertFalse(weak(), "World leaked a reference")

test/utils/test_caches.py

@@ -0,0 +1,66 @@
+# Tests for caches in Utils.py
+
+import unittest
+from typing import Any
+
+from Utils import cache_argsless, cache_self1
+
+
+class TestCacheArgless(unittest.TestCase):
+    def test_cache(self) -> None:
+        @cache_argsless
+        def func_argless() -> object:
+            return object()
+
+        self.assertTrue(func_argless() is func_argless())
+
+    if __debug__:  # assert only available with __debug__
+        def test_invalid_decorator(self) -> None:
+            with self.assertRaises(Exception):
+                @cache_argsless  # type: ignore[arg-type]
+                def func_with_arg(_: Any) -> None:
+                    pass
+
+
+class TestCacheSelf1(unittest.TestCase):
+    def test_cache(self) -> None:
+        class Cls:
+            @cache_self1
+            def func(self, _: Any) -> object:
+                return object()
+
+        o1 = Cls()
+        o2 = Cls()
+        self.assertTrue(o1.func(1) is o1.func(1))
+        self.assertFalse(o1.func(1) is o1.func(2))
+        self.assertFalse(o1.func(1) is o2.func(1))
+
+    def test_gc(self) -> None:
+        # verify that we don't keep a global reference
+        import gc
+        import weakref
+
+        class Cls:
+            @cache_self1
+            def func(self, _: Any) -> object:
+                return object()
+
+        o = Cls()
+        _ = o.func(o)  # keep a hard ref to the result
+        r = weakref.ref(o)  # keep weak ref to the cache
+        del o  # remove hard ref to the cache
+        gc.collect()
+        self.assertFalse(r())  # weak ref should be dead now
+
+    if __debug__:  # assert only available with __debug__
+        def test_no_self(self) -> None:
+            with self.assertRaises(Exception):
+                @cache_self1  # type: ignore[arg-type]
+                def func() -> Any:
+                    pass
+
+        def test_too_many_args(self) -> None:
+            with self.assertRaises(Exception):
+                @cache_self1  # type: ignore[arg-type]
+                def func(_1: Any, _2: Any, _3: Any) -> Any:
+                    pass