Use strict_exception_groups=False instead

add test and news

newsfragments/397.bugfix.rst

@@ -0,0 +1 @@
+Minimum Trio version increased to 0.22.0 to use ``strict_exception_groups=False`` internally.

setup.cfg

@@ -34,7 +34,7 @@ classifiers =
 packages = find:
 include_package_data = True
 install_requires =
-    trio >= 0.18.0
+    trio >= 0.22.0
     outcome
     attrs >= 17.3.0
     cffi; os_name == 'nt' and implementation_name != 'pypy'

trio_parallel/_proc.py

@@ -70,25 +70,22 @@ async def start(self):
         self._child_recv_pipe.close()
 
         # The following is mainly needed in the case of accidental recursive spawn
-        async def wait_for_ack():
+        async def wait_then_fail():
+            await self.wait()
+            raise BrokenWorkerProcessError("Worker failed to start", self.proc)
+
+        async with trio.open_nursery(strict_exception_groups=False) as nursery:
+            nursery.start_soon(wait_then_fail)
             try:
                 code = await self._receive_chan.receive()
-                assert code == tp_workers.ACK
             except BaseException:
                 self.kill()
                 with trio.CancelScope(shield=True):
                     await self.wait()  # noqa: TRIO102
                 raise
+            assert code == tp_workers.ACK
             nursery.cancel_scope.cancel()
 
-        exitcode = None
-        async with trio.open_nursery() as nursery:
-            nursery.start_soon(wait_for_ack)
-            exitcode = await self.wait()
-            nursery.cancel_scope.cancel()
-        if exitcode is not None:
-            raise BrokenWorkerProcessError("Worker failed to start", self.proc)
-
     async def run_sync(self, sync_fn: Callable, *args) -> Optional[Outcome]:
         try:
             job = dumps((sync_fn, args), protocol=HIGHEST_PROTOCOL)

trio_parallel/_tests/test_defaults.py

@@ -214,6 +214,8 @@ def test_startup_failure_doesnt_hang(tmp_path):
     )
     assert not result.stdout
     assert b"An attempt has been made to start a new process" in result.stderr
+    assert b"ExceptionGroup" not in result.stderr
+    assert b"MultiError" not in result.stderr
     assert result.returncode