Issue #11459: A `bufsize` value of 0 in subprocess.Popen() really creates
unbuffered pipes, such that select() works properly on them.
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 3cc387b..01e670e 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -1216,6 +1216,22 @@
" non-zero with this error:\n%s" %
stderr.decode('utf8'))
+ def test_select_unbuffered(self):
+ # Issue #11459: bufsize=0 should really set the pipes as
+ # unbuffered (and therefore let select() work properly).
+ select = support.import_module("select")
+ p = subprocess.Popen([sys.executable, "-c",
+ 'import sys;'
+ 'sys.stdout.write("apple")'],
+ stdout=subprocess.PIPE,
+ bufsize=0)
+ f = p.stdout
+ try:
+ self.assertEqual(f.read(4), b"appl")
+ self.assertIn(f, select.select([f], [], [], 0.0)[0])
+ finally:
+ p.wait()
+
@unittest.skipUnless(mswindows, "Windows specific tests")
class Win32ProcessTestCase(BaseTestCase):