bpo-46470: remove unused branch from typing._remove_dups_flatten

[sobolevn]

CC @corona10 as my mentor.

https://bugs.python.org/issue46470

[sobolevn]

I am lucky today, all my PRs trigger very rare error in test_asyncio 😆

[JelleZijlstra]

I think this happened in 3.6:

In [22]: typing_inspect.get_args(Union[List[str], Set[str]])
Out[22]: ((typing.List, str), (typing.Set, str))

[sobolevn]

This test officially won:

 ======================================================================
FAIL: test_sendfile_close_peer_in_the_middle_of_receiving (test.test_asyncio.test_sendfile.ProactorEventLoopTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\a\cpython\cpython\Lib\test\test_asyncio\test_sendfile.py", line 461, in test_sendfile_close_peer_in_the_middle_of_receiving
    with self.assertRaises(ConnectionError):
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: ConnectionError not raised

No idea why it happens so often today. I've tried to re-trigger the CI twice, but it still fails.

[gvanrossum]

Could it be that bpo-46409 / GH-30633 destabilized that test even more? Is there evidence in other PRs that this is happening more often?

If it's timing related (as sounds likely) it could also have to do with congestion in the fleet of machines where GitHub Actions are run. Possibly someone should open a separate bug. Even if it's not any PR's fault, the asyncio tests are clearly more flaky than most, and are causing a fair amount of CI churn.

[gvanrossum]

Trying once more.

[AlexWaygood]

Is there evidence in other PRs that this is happening more often?

Anecdotally, from what I can tell, it does seem to have been occurring much more often in the last few weeks.

[gvanrossum]

So not Mark's generators PR, but maybe something else. Any chance of plotting these occurrences? That could make it obvious where to look. (But getting the data to plot might be complicated.)

[sobolevn]

Me-test: 1-1 😆
#30801

Now, it should be fine!

[Fidget-Spinner]

Wow, that's an interesting blast from the past.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM64 macOS 3.x has failed when building commit c144d93.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/725/builds/835) and take a look at the build logs.
4. Check if the failure is related to this commit (c144d93) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/725/builds/835

Summary of the results of the build (if available):

== Tests result: ENV CHANGED ==

411 tests OK.

10 slowest tests:

• test_concurrent_futures: 3 min 42 sec
• test_multiprocessing_spawn: 2 min 31 sec
• test_multiprocessing_forkserver: 1 min 52 sec
• test_unparse: 1 min 32 sec
• test_asyncio: 1 min 14 sec
• test_tokenize: 1 min 14 sec
• test_lib2to3: 57.6 sec
• test_logging: 57.3 sec
• test_capi: 50.8 sec
• test_ssl: 48.9 sec

1 test altered the execution environment:
test_ftplib

17 tests skipped:
test_dbm_gnu test_devpoll test_epoll test_gdb test_ioctl
test_msilib test_multiprocessing_fork test_ossaudiodev test_spwd
test_startfile test_tix test_tk test_ttk_guionly test_winconsoleio
test_winreg test_winsound test_zipfile64

Total duration: 8 min 28 sec

Click to see traceback logs

Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/multiprocessing/resource_tracker.py", line 209, in main
    cache[rtype].remove(name)
    ^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: '/psm_97ac8430'


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/asyncore.py", line 90, in read
    obj.handle_read_event()
    ^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_ftplib.py", line 384, in handle_read_event
    self._do_ssl_handshake()
    ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_ftplib.py", line 345, in _do_ssl_handshake
    self.socket.do_handshake()
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/ssl.py", line 1345, in do_handshake
    self._sslobj.do_handshake()
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
ssl.SSLZeroReturnError: TLS/SSL connection has been closed (EOF) (_ssl.c:998)


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/multiprocessing/resource_tracker.py", line 209, in main
    cache[rtype].remove(name)
    ^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: '/psm_6137da71'


Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/threading.py", line 1031, in _bootstrap_inner
    self.run()
    ^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_ftplib.py", line 298, in run
    asyncore.loop(timeout=0.1, count=1)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/asyncore.py", line 214, in loop
    poll_fun(timeout, map)
    ^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/asyncore.py", line 157, in poll
    read(obj)
    ^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/asyncore.py", line 94, in read
    obj.handle_error()
    ^^^^^^^^^^^^^^^^^^
  File "/Users/buildbot/buildarea/3.x.pablogsal-macos-m1.macos-with-brew/build/Lib/test/test_ftplib.py", line 421, in handle_error
    raise Exception
    ^^^^^^^^^^^^^^^
Exception
k

[JelleZijlstra]

That looks unrelated to this PR.