Add weakref-based AutoUnload class to allow instances to be garbage collected

addons/source-python/packages/source-python/core/__init__.py

@@ -19,6 +19,8 @@
 from platform import system
 #   Sys
 import sys
+#   Weakref
+import weakref
 
 # Site-Packages Imports
 #   ConfigObj
@@ -85,12 +87,16 @@ def __new__(cls, *args, **kwargs):
         # Get the calling module
         caller = getmodule(stack()[1][0])
 
-        # Set the _calling_module attribute for the instance
-        _module_instances[caller.__name__].append(self)
+        # Call class-specific logic for adding the instance.
+        self._add_instance(caller.__name__)
 
         # Return the instance
         return self
 
+    def _add_instance(self, caller):
+        """Add the instance to _module_instances."""
+        _module_instances[caller].append(self)
+
     def _unload_instance(self):
         """Base _unload_instance implementation."""
         raise NotImplementedError(
@@ -101,6 +107,36 @@ def _unload_instance(self):
             'have its own implementation of an _unload_instance method.')
 
 
+class WeakAutoUnload(AutoUnload):
+    """Subclass of AutoUnload used to unload specific instances when all
+    references to the instance are deleted.
+    """
+
+    def new(cls, *args, **kwargs):
+        self = super().__new__(cls)
+        self.___unloaded = False
+
+        return self
+
+    def __del__(self):
+        """Overwrite __del__ to automatically unload the instance when garbage
+        collected.
+        """
+        self._unload_instance()
+
+    def _add_instance(self, caller):
+        """Add the instance to _module_instances."""
+        # Use a weakref proxy so that the instance will get garbage collected
+        # when this is the only reference left.
+        _module_instances[caller].append(weakref.proxy(self))
+
+    def _unload_instance(self):
+        # Prevent unloading more than once.
+        if not self.___unloaded:
+            self.___unloaded = True
+            super()._unload_instance(self)
+
+
 class GameConfigObj(ConfigObj):
     """Class used to parse specific game data."""
 

addons/source-python/packages/source-python/listeners/tick.py

@@ -16,7 +16,7 @@
 
 # Source.Python Imports
 #   Core
-from core import AutoUnload
+from core import AutoUnload, WeakAutoUnload
 #   Hooks
 from hooks.exceptions import except_hooks
 #   Listeners
@@ -78,7 +78,7 @@ def add(self, delay):
 _delay_manager = _DelayManager()
 
 
-class Delay(AutoUnload):
+class Delay(WeakAutoUnload):
     """Execute a callback after a given delay."""
 
     def __init__(self, delay, callback, *args, **kwargs):

addons/source-python/packages/source-python/plugins/manager.py

@@ -189,6 +189,9 @@ def _remove_modules(self, plugin_name):
             for instance in instances:
                 try:
                     instance._unload_instance()
+                # Instance is an expired weak reference proxy.
+                except ReferenceError:
+                    pass
                 except NotImplementedError:
                     # Print the error to console, but allow all
                     # other AutoUnload instances to be unloaded