GH-100133: fix `asyncio` subprocess losing `stderr` and `stdout` output (GH-100154)

(cherry picked from commit a7715ccfba5b86ab09f86ec56ac3755c93b46b48)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/Lib/test/test_asyncio/test_subprocess.py b/Lib/test/test_asyncio/test_subprocess.py
index f71ad72..bea2314 100644
--- a/Lib/test/test_asyncio/test_subprocess.py
+++ b/Lib/test/test_asyncio/test_subprocess.py
@@ -684,6 +684,23 @@ class SubprocessMixin:
 
         self.assertIsNone(self.loop.run_until_complete(execute()))
 
+    def test_subprocess_communicate_stdout(self):
+        # See https://github.com/python/cpython/issues/100133
+        async def get_command_stdout(cmd, *args):
+            proc = await asyncio.create_subprocess_exec(
+                cmd, *args, stdout=asyncio.subprocess.PIPE,
+            )
+            stdout, _ = await proc.communicate()
+            return stdout.decode().strip()
+
+        async def main():
+            outputs = [f'foo{i}' for i in range(10)]
+            res = await asyncio.gather(*[get_command_stdout(sys.executable, '-c',
+                                        f'print({out!r})') for out in outputs])
+            self.assertEqual(res, outputs)
+
+        self.loop.run_until_complete(main())
+
 
 if sys.platform != 'win32':
     # Unix