SomberNight 87540dbe3e util.EventListener: store WeakMethods in CallbackManager to avoid leaks ...

This patch changes the CallbackManager to use WeakMethods (weakrefs) to
break the ref cycle and allow the GC to clean up the wallet objects.
unregister_callbacks() will also get called automatically, from
EventListener.__del__, to clean up the CallbackManager.

I also added a few unit tests for this.

fixes https://github.com/spesmilo/electrum/issues/10427

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original problem:

In many subclasses of `EventListener`, such as `Abstract_Wallet`, `LNWatcher`,
`LNPeerManager`, we call `register_callbacks()` in `__init__`.
`unregister_callbacks()` is usually called in the `stop()` method.

Example - consider the wallet object:
- `Abstract_Wallet.__init__()` calls `register_callbacks()`
- there is a `start_network()` method
- there is a `stop()` method, which calls `unregister_callbacks()`
- typically the wallet API user only calls `stop()` if they also called
  `start_network()`.

This means the callbacks are often left registered, leading to the wallet
objects not getting GC-ed. The GC won't clean them up as
`util.callback_mgr.callbacks` stores strong refs to instance methods
of `Abstract_Wallet`, hence strong refs to the `Abstract_Wallet` objects.

An annoying example is `daemon.check_password_for_directory`, which
potentially creates wallet objects for all wallet files in the datadir.
It simply constructs the wallets, does not call `start_network()` and
neither does it call `stop()`.

2026-01-21 17:49:41 +00:00

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