gh-132063: ProcessPoolExecutor swallows falsy Exceptions

Lib/concurrent/futures/_base.py

@@ -390,7 +390,7 @@ def done(self):
             return self._state in [CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED]
 
     def __get_result(self):
-        if self._exception:
+        if self._exception is not None:
             try:
                 raise self._exception
             finally:

Lib/concurrent/futures/process.py

@@ -440,7 +440,7 @@ def process_result_item(self, result_item):
         work_item = self.pending_work_items.pop(result_item.work_id, None)
         # work_item can be None if another process terminated (see above)
         if work_item is not None:
-            if result_item.exception:
+            if result_item.exception is not None:
                 work_item.future.set_exception(result_item.exception)
             else:
                 work_item.future.set_result(result_item.result)

Lib/test/test_concurrent_futures/test_process_pool.py

@@ -337,6 +337,20 @@ def test_force_shutdown_workers_stops_pool(self, function_name):
                 if not worker_process.is_alive():
                     break
 
+    class MyException(Exception):
+        def __bool__(self):
+            return False
+
+    @classmethod
+    def raiser(cls):
+        raise cls.MyException("foo")
+
+    def test_swallows_falsy_exceptions(self):
+        # fix gh-132063 issue
+        with self.assertRaisesRegex(self.MyException, "foo"):
+            with self.executor_type(max_workers=1) as executor:
+                executor.submit(self.raiser).result()
+
 
 create_executor_tests(globals(), ProcessPoolExecutorTest,
                       executor_mixins=(ProcessPoolForkMixin,

Lib/test/test_concurrent_futures/test_thread_pool.py

@@ -112,6 +112,19 @@ def log_n_wait(ident):
         # ident='third' is cancelled because it remained in the collection of futures
         self.assertListEqual(log, ["ident='first' started", "ident='first' stopped"])
 
+    class MyException(Exception):
+        def __bool__(self):
+            return False
+
+    @classmethod
+    def raiser(cls):
+        raise cls.MyException("foo")
+
+    def test_swallows_falsy_exceptions(self):
+        # fix gh-132063 issue
+        with self.assertRaisesRegex(self.MyException, "foo"):
+            with self.executor_type(max_workers=1) as executor:
+                executor.submit(self.raiser).result()
 
 def setUpModule():
     setup_module()

Misc/NEWS.d/next/Library/2025-04-05-15-05-09.gh-issue-132063.KHnslU.rst

@@ -0,0 +1 @@
+Fix tests of exception attribute in :method:`process_result_item`of :class:`_ExecutorManagerThread` and :method:`__get_result` of :class:`Future` in module :lib:`concurrent`.