bpo-35424: emit ResourceWarning at multiprocessing.Pool destruction (GH-10974)

multiprocessing.Pool destructor now emits ResourceWarning
if the pool is still running.

1 files changed, 16 insertions, 0 deletions

diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index b5597d5..7341131 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -2577,6 +2577,22 @@ class _TestPool(BaseTestCase):
                 pass
         pool.join()
 
+    def test_resource_warning(self):
+        if self.TYPE == 'manager':
+            self.skipTest("test not applicable to manager")
+
+        pool = self.Pool(1)
+        pool.terminate()
+        pool.join()
+
+        # force state to RUN to emit ResourceWarning in __del__()
+        pool._state = multiprocessing.pool.RUN
+
+        with support.check_warnings(('unclosed running multiprocessing pool',
+                                     ResourceWarning)):
+            pool = None
+            support.gc_collect()
+
 
 def raising():
     raise KeyError("key")