Method finalize_remove_modules

crates/vm/src/vm/mod.rs:1317–1348

Phase 2: Set all sys.modules values to None and collect weakrefs. No strong refs are kept — modules are freed when removed from sys.modules (if nothing else references them), allowing GC to collect their cycles.

(&self)

    /// No strong refs are kept — modules are freed when removed from sys.modules
    /// (if nothing else references them), allowing GC to collect their cycles.
    fn finalize_remove_modules(&self) -> Vec<(String, PyRef<PyWeak>)> {
        let mut module_weakrefs = Vec::new();

        let Ok(modules) = self.sys_module.get_attr(identifier!(self, modules), self) else {
            return module_weakrefs;
        };
        let Some(modules_dict) = modules.downcast_ref::<PyDict>() else {
            return module_weakrefs;
        };

        let none = self.ctx.none();
        let items: Vec<_> = modules_dict.into_iter().collect();

        for (key, value) in items {
            let name = key
                .downcast_ref::<PyUtf8Str>()
                .map(|s| s.as_str().to_owned())
                .unwrap_or_default();

            // Save weakref to module (for later dict clearing)
            if value.downcast_ref::<PyModule>().is_some()
                && let Ok(weak) = value.downgrade(None, self)
            {
                module_weakrefs.push((name, weak));
            }

            // Set the value to None in sys.modules
            let _ = modules_dict.set_item(&*key, none.clone(), self);
        }

        module_weakrefs
    }

    /// Phase 3: Clear sys.modules dict.
    fn finalize_clear_modules_dict(&self) {