bpo-31158: Fix nondeterministic read in test_pty by diekmann · Pull Request #3808 · python/cpython (original) (raw)

Thanks @pitrou for the suggestion. The following also works on my machine:

diff --git a/Lib/test/test_pty.py b/Lib/test/test_pty.py index f283e19..ee9b589 100644 --- a/Lib/test/test_pty.py +++ b/Lib/test/test_pty.py @@ -10,6 +10,7 @@ import sys import select import signal import socket +import io import unittest TEST_STRING_1 = b"I wish to buy a fish license.\n" @@ -92,17 +93,18 @@ class PtyTest(unittest.TestCase): # Restore the original flags. os.set_blocking(master_fd, blocking) - debug("Writing to slave_fd") - os.write(slave_fd, TEST_STRING_1) - s1 = os.read(master_fd, 1024) - self.assertEqual(b'I wish to buy a fish license.\n', - normalize_output(s1))

•    debug("Writing chunked output")

•    os.write(slave_fd, TEST_STRING_2[:5])

•    os.write(slave_fd, TEST_STRING_2[5:])

•    s2 = os.read(master_fd, 1024)

•    self.assertEqual(b'For my pet fish, Eric.\n', normalize_output(s2))

•    with io.FileIO(master_fd, mode='rb', closefd=False) as master:

•        debug("Writing to slave_fd")

•        os.write(slave_fd, TEST_STRING_1)

•        s1 = master.readline()

•        self.assertEqual(b'I wish to buy a fish license.\n',

•                         normalize_output(s1))

•        debug("Writing chunked output")

•        os.write(slave_fd, TEST_STRING_2[:5])

•        os.write(slave_fd, TEST_STRING_2[5:])

•        s2 = master.readline()

•        self.assertEqual(b'For my pet fish, Eric.\n', normalize_output(s2))
  
     os.close(slave_fd)
     os.close(master_fd)

Which version is better?

Problem in version 1:

• Re-implementing readline

Problem in version 2:

• Depends on the io module, while the pty module usually only uses the raw os.read and os.write calls. A failure could make debugging harder (is it the pty module or a change in the io module?).
• I don't like that we have both, master and master_fd hanging around