From 46fa1b2b80429367302c4b17db56cfb1888a0129 Mon Sep 17 00:00:00 2001
From: David Hewitt <mail@davidhewitt.dev>
Date: Tue, 19 Dec 2023 16:16:13 +0000
Subject: [PATCH 1/2] add test which is broken with gevent

---
 pytests/pyproject.toml     |  1 +
 pytests/src/misc.rs        | 12 +++++++++++-
 pytests/tests/test_misc.py | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/pytests/pyproject.toml b/pytests/pyproject.toml
index fb1ac3db..4d5b42bf 100644
--- a/pytests/pyproject.toml
+++ b/pytests/pyproject.toml
@@ -20,6 +20,7 @@ classifiers = [
 
 [project.optional-dependencies]
 dev = [
+    "gevent>=23.9.1",
     "hypothesis>=3.55",
     "pytest-asyncio>=0.21",
     "pytest-benchmark>=3.4",
diff --git a/pytests/src/misc.rs b/pytests/src/misc.rs
index 029e8b16..548c5ceb 100644
--- a/pytests/src/misc.rs
+++ b/pytests/src/misc.rs
@@ -1,4 +1,4 @@
-use pyo3::prelude::*;
+use pyo3::{prelude::*, types::PyDict};
 use std::borrow::Cow;
 
 #[pyfunction]
@@ -17,10 +17,20 @@ fn accepts_bool(val: bool) -> bool {
     val
 }
 
+#[pyfunction]
+fn get_item_and_run_callback(dict: &PyDict, callback: &PyAny) -> PyResult<()> {
+    let item = dict.get_item("key")?.expect("key not found in dict");
+    let string = item.to_string();
+    callback.call0()?;
+    assert_eq!(item.to_string(), string);
+    Ok(())
+}
+
 #[pymodule]
 pub fn misc(_py: Python<'_>, m: &PyModule) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(issue_219, m)?)?;
     m.add_function(wrap_pyfunction!(get_type_full_name, m)?)?;
     m.add_function(wrap_pyfunction!(accepts_bool, m)?)?;
+    m.add_function(wrap_pyfunction!(get_item_and_run_callback, m)?)?;
     Ok(())
 }
diff --git a/pytests/tests/test_misc.py b/pytests/tests/test_misc.py
index 06b2ce73..2f6cee63 100644
--- a/pytests/tests/test_misc.py
+++ b/pytests/tests/test_misc.py
@@ -2,6 +2,7 @@ import importlib
 import platform
 import sys
 
+import gevent
 import pyo3_pytests.misc
 import pytest
 
@@ -64,3 +65,39 @@ def test_accepts_numpy_bool():
     assert pyo3_pytests.misc.accepts_bool(False) is False
     assert pyo3_pytests.misc.accepts_bool(numpy.bool_(True)) is True
     assert pyo3_pytests.misc.accepts_bool(numpy.bool_(False)) is False
+
+
+class ArbitraryClass:
+    worker_id: int
+    iteration: int
+
+    def __init__(self, worker_id: int, iteration: int):
+        self.worker_id = worker_id
+        self.iteration = iteration
+
+    def __repr__(self):
+        return f"ArbitraryClass({self.worker_id}, {self.iteration})"
+
+    def __del__(self):
+        print("del", self.worker_id, self.iteration)
+
+
+def test_gevent():
+    def worker(worker_id: int) -> None:
+        for iteration in range(2):
+            d = {"key": ArbitraryClass(worker_id, iteration)}
+
+            def arbitrary_python_code():
+                # remove the dictionary entry so that the class value can be
+                # garbage collected
+                del d["key"]
+                print("gevent sleep", worker_id, iteration)
+                gevent.sleep(0)
+                print("after gevent sleep", worker_id, iteration)
+
+            print("start", worker_id, iteration)
+            pyo3_pytests.misc.get_item_and_run_callback(d, arbitrary_python_code)
+            print("end", worker_id, iteration)
+
+    workers = [gevent.spawn(worker, i) for i in range(2)]
+    gevent.joinall(workers)

From 49d7718823b6206d81b56fceac0087705350f009 Mon Sep 17 00:00:00 2001
From: David Hewitt <mail@davidhewitt.dev>
Date: Sat, 23 Dec 2023 22:10:01 +0000
Subject: [PATCH 2/2] demonstrate switching to `Bound` API resolves `gevent`
 crash

---
 pytests/src/misc.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/pytests/src/misc.rs b/pytests/src/misc.rs
index 548c5ceb..bd941461 100644
--- a/pytests/src/misc.rs
+++ b/pytests/src/misc.rs
@@ -18,7 +18,11 @@ fn accepts_bool(val: bool) -> bool {
 }
 
 #[pyfunction]
-fn get_item_and_run_callback(dict: &PyDict, callback: &PyAny) -> PyResult<()> {
+fn get_item_and_run_callback(dict: Bound<'_, PyDict>, callback: Bound<'_, PyAny>) -> PyResult<()> {
+    // This function gives the opportunity to run a pure-Python callback so that
+    // gevent can instigate a context switch. This had problematic interactions
+    // with PyO3's removed "GIL Pool".
+    // For context, see https://github.com/PyO3/pyo3/issues/3668
     let item = dict.get_item("key")?.expect("key not found in dict");
     let string = item.to_string();
     callback.call0()?;