refactor: keep interpreter exit signaling native (#1277)

Replace the private process-wide threading.Event with an atomic flag while preserving existing shutdown hooks, polling, waits and public interfaces. Retire its four Python-crossing allowances and document the existing monotonic process-wide signal.

Amp-Thread-ID: https://ampcode.com/threads/T-01a18715-4e00-708e-a87d-6bd109748d66

Author: kvlonge

crates/sqlbuild-python/src/bindings/_helpers/event_exporting/dispatcher.rs

@@ -333,7 +333,7 @@ fn limits(options: &KeywordArguments<'_>) -> PyResult<Limits> {
 /// Stop every live dispatcher's threads and join them before finalization ends them inside native code.
 #[pyfunction]
 pub(crate) fn stop_event_exporter_threads(py: Python<'_>) -> PyResult<()> {
-    signal_interpreter_exit(py)?;
+    signal_interpreter_exit();
     let mut threads: Vec<Bound<'_, PyAny>> = Vec::new();
     for thread in imported(py, "threading", "enumerate")?
         .call0()?
@@ -483,7 +483,7 @@ impl Shared {
         let threads: Vec<Py<PyAny>> = {
             let _held = self.hold(py)?;
             loop {
-                if interpreter_exiting(py)? {
+                if interpreter_exiting() {
                     return Ok(());
                 }
                 let state = self.locked()?;
@@ -597,7 +597,7 @@ impl Shared {
                 Err(error) if error.is_instance(py, &empty) => {}
                 Err(error) => return Err(error),
             }
-            if interpreter_exiting(py)? {
+            if interpreter_exiting() {
                 return Ok(Delivery::Abandoned);
             }
         }

crates/sqlbuild-python/src/bindings/_helpers/native_threads/exit_signal.rs

@@ -1,30 +1,15 @@
 //! The interpreter-exit signal native waits poll so Python daemon threads leave native frames before finalization.
 
-use pyo3::prelude::{Bound, Py, PyAny, PyAnyMethods, PyResult, Python};
-use pyo3::sync::PyOnceLock;
+use std::sync::atomic::{AtomicBool, Ordering};
 
-use crate::bindings::_helpers::boundary::python_calls::imported;
-
-static EXIT_SIGNAL: PyOnceLock<Py<PyAny>> = PyOnceLock::new();
-
-/// The process-wide `threading.Event` set once interpreter exit begins.
-fn exit_signal(py: Python<'_>) -> PyResult<Bound<'_, PyAny>> {
-    EXIT_SIGNAL
-        .get_or_try_init(py, || {
-            imported(py, "threading", "Event")?
-                .call0()
-                .map(Bound::unbind)
-        })
-        .map(|signal| signal.bind(py).clone())
-}
+static EXIT_SIGNAL: AtomicBool = AtomicBool::new(false);
 
 /// Whether an exit hook has started stopping native daemon threads.
-pub(crate) fn interpreter_exiting(py: Python<'_>) -> PyResult<bool> {
-    exit_signal(py)?.call_method0("is_set")?.is_truthy()
+pub(crate) fn interpreter_exiting() -> bool {
+    EXIT_SIGNAL.load(Ordering::SeqCst)
 }
 
 /// Tell every native wait to stop waiting on Python work that may outlive the interpreter.
-pub(crate) fn signal_interpreter_exit(py: Python<'_>) -> PyResult<()> {
-    exit_signal(py)?.call_method0("set")?;
-    Ok(())
+pub(crate) fn signal_interpreter_exit() {
+    EXIT_SIGNAL.store(true, Ordering::SeqCst);
 }

crates/sqlbuild-python/src/bindings/_helpers/output_capture/dispatcher.rs

@@ -122,7 +122,7 @@ fn delivering_thread(py: Python<'_>) -> PyResult<bool> {
 /// Stop every capture worker and join it before finalization ends it inside native code.
 #[pyfunction]
 fn stop_output_capture_threads(py: Python<'_>) -> PyResult<()> {
-    signal_interpreter_exit(py)?;
+    signal_interpreter_exit();
     let mut threads: Vec<Bound<'_, PyAny>> = Vec::new();
     for thread in imported(py, "threading", "enumerate")?
         .call0()?

crates/sqlbuild-python/src/bindings/_helpers/planner_entries/test_planning.rs

@@ -215,7 +215,7 @@ pub(crate) fn start_planning(
 /// Join SQL test planning threads at exit: finalization ending one inside native planning aborts.
 #[pyfunction]
 fn join_sql_test_planning_threads(py: Python<'_>) -> PyResult<()> {
-    signal_interpreter_exit(py)?;
+    signal_interpreter_exit();
     let threads: &PlanningThreads = planning_threads(py)?.get();
     py.detach(|| threads.wait(PLANNING_EXIT_JOIN));
     Ok(())

fensu.toml

@@ -1574,6 +1574,12 @@ rule = "FPRSL105"
 path = "crates/sqlbuild-analysis/src/sql_tokens/main/builtin_function_names.rs"
 reason = "This test-support entry exists only for the SQL lint tests in sqlbuild-rules, which the analyzer does not count as importers."
 
+[[targets.rust.rule_exceptions]]
+rule = "FPRSS130"
+path = "crates/sqlbuild-python/src/bindings/_helpers/native_threads/exit_signal.rs"
+symbols = ["signal_interpreter_exit"]
+reason = "The existing interpreter-exit signal is process-wide and monotonic: every native daemon wait must observe any exit hook before Python finalization. The atomic replaces the same global threading.Event, not per-command lifecycle state."
+
 [targets.rust.rule_options.FPRSR311]
 allowed_entries = [
     "Cargo.toml",
@@ -1990,7 +1996,6 @@ pending_budgets = [
     "crates/sqlbuild-python/src/bindings/_helpers/model_config/template_data.rs=4",
     "crates/sqlbuild-python/src/bindings/_helpers/model_config/typed_config.rs=2",
     "crates/sqlbuild-python/src/bindings/_helpers/model_config/unicode_environment.rs=4",
-    "crates/sqlbuild-python/src/bindings/_helpers/native_threads/exit_signal.rs=4",
     "crates/sqlbuild-python/src/bindings/_helpers/output_capture/context.rs=6",
     "crates/sqlbuild-python/src/bindings/_helpers/output_capture/dispatcher.rs=33",
     "crates/sqlbuild-python/src/bindings/_helpers/output_capture/records.rs=16",