Remove asyncore, asynchat and smtpd modules

[Mariatta]

BPO	28533
Nosy	@warsaw, @orsenthil, @vstinner, @asvetlov, @1st1, @grzgrzgrz3, @Mariatta, @nanjekyejoannah, @aeros, @jacksonriley, @OhSoDank, @iritkatriel
PRs	bpo-28533: Remove asyncore, asynchat, smtpd modules #29521 Revert "bpo-28533: Remove asyncore, asynchat, smtpd modules (GH-29521)" #29951

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2016-10-25.18:32:04.420>
labels = ['3.11', 'tests', 'expert-asyncio']
title = 'Remove asyncore, asynchat and smtpd modules'
updated_at = <Date 2022-02-24.13:39:30.092>
user = 'https://github.com/Mariatta'

bugs.python.org fields:

activity = <Date 2022-02-24.13:39:30.092>
actor = 'vstinner'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Tests', 'asyncio']
creation = <Date 2016-10-25.18:32:04.420>
creator = 'Mariatta'
dependencies = []
files = []
hgrepos = []
issue_num = 28533
keywords = ['patch']
message_count = 37.0
messages = ['279439', '291907', '291908', '294710', '294712', '294771', '294773', '356355', '356364', '356369', '357088', '379342', '396295', '396297', '396319', '396323', '404575', '406159', '406160', '406161', '406162', '406170', '406173', '406208', '406210', '406213', '406214', '406215', '406372', '406377', '406434', '407559', '407560', '407897', '407900', '407915', '413909']
nosy_count = 12.0
nosy_names = ['barry', 'orsenthil', 'vstinner', 'asvetlov', 'yselivanov', 'grzgrzgrz3', 'Mariatta', 'nanjekyejoannah', 'aeros', 'jacksonriley', 'dankreso', 'iritkatriel']
pr_nums = ['29521', '29951']
priority = 'normal'
resolution = None
stage = 'resolved'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue28533'
versions = ['Python 3.11']

• PR: gh-72719: Remove deprecated asyncore and asynchat modules #96580

[Mariatta]

Deprecation warning was added to asyncore in https://bugs.python.org/issue25002

asyncore is still used in several tests and should be replaced.

[vstinner]

asyncore is still used in several tests and should be replaced.

Here is the list of Python files using asyncore:

haypo@selma$ grep -l asyncore $(find -name "*.py")
./Lib/asyncore.py
./Lib/asynchat.py
./Lib/test/test_smtpd.py
./Lib/test/test_asyncore.py
./Lib/test/test_smtplib.py
./Lib/test/test_os.py
./Lib/test/test_ssl.py
./Lib/test/test_logging.py
./Lib/test/libregrtest/save_env.py
./Lib/test/test_asynchat.py
./Lib/test/test_pyclbr.py
./Lib/test/test_support.py
./Lib/test/test_poplib.py
./Lib/test/test_ftplib.py
./Lib/smtpd.py

smtpd has been rewritten with asyncio:
http://aiosmtpd.readthedocs.io/

The documentation of the smtpd module already points to aiosmtpd.

libregrtest/save_env.py only checks that asyncore.socket_map is not modified, we can keep it until asyncore is really removed.

test_support.py only tests that it's possible to have a "clean" import of asyncore, it can be easily be replaced later.

The list can reduced to:

./Lib/test/test_smtplib.py
./Lib/test/test_os.py
./Lib/test/test_ssl.py
./Lib/test/test_logging.py
./Lib/test/test_pyclbr.py
./Lib/test/test_poplib.py
./Lib/test/test_ftplib.py

[vstinner]

asyncore was modified to emit a DeprecationWarning:
http://bugs.python.org/issue25002#msg279417

But then a lot of code starts with to fail -Werror.

Copy of Martin Panter's msg279469:

I normally run the tests with -Werror, and the failures I get are:

• test_ssl, test_smtplib, test_poplib, test_logging, test_ftplib, test_support: tests use asyncore
• test_os: test uses asynchat (When you import asynchat, the first error complains about importing asyncore, there are actually two warnings)
• test_all: This seems to ignore DeprecationWarning; perhaps an exception for PendingDeprecationWarning should also be added?
• test_asyncore and test_asynchat: Obviously these have to still test the modules, so they should anticipate the warnings, perhaps using Serhiy’s code
• test_smtpd: smtpd module itself uses asyncore; see bpo-25008

[grzgrzgrz3]

I would like to work on this issue.

I think it's a good idea to split this task into few parts/PR.

Let me start from ./Lib/test/test_poplib.py.

What about rewriting pop3 server stub using asyncio, i think requests could be handled synchronously, there will be no benefits from asynchronous.

Please let me know what you think.

[vstinner]

I think it's a good idea to split this task into few parts/PR. Let me start from ./Lib/test/test_poplib.py.

Once you have a patch, open a new issue and mention it here.

[grzgrzgrz3]

./Lib/test/test_poplib.py
sub-issue bpo-28533

[grzgrzgrz3]

./Lib/test/test_poplib.py
sub-issue bpo-30514

Fixed issue number from previous comment

[OhSoDank]

Hi, is this still open?

I'm happy to work on replacing asyncore usage in one of the other test files.

[nanjekyejoannah]

@dankreso, the issue is still open and no one has claimed it yet. So feel free to open a pull request.

[aeros]

I'm happy to work on replacing asyncore usage in one of the other test files.

Sounds good, just let us know which one(s) you're working on. (:

[jacksonriley]

Lib/test/test_pyclbr.py - subissue bpo-38866
A trivial one!

[aeros]

Since this issue is now a significant blocker for PEP-594 (remove stdlib dead batteries, which includes asyncore and asynchat), I'm going to prioritize working on this and assign it to myself.

[iritkatriel]

If the tests are the only thing blocking removal, does it make sense to move asyncore and asynchat to test.support and get on with removing them from the stdlib?

[vstinner]

Irit:

If the tests are the only thing blocking removal, does it make sense to move asyncore and asynchat to test.support and get on with removing them from the stdlib?

Yes, it makes sense and it can be done right now, since asynchat/asyncore is deprecated since Python 3.6.

[iritkatriel]

There is actually one usage outside of the tests: Lib/smtpd.py

There is a note in the doc saying " The aiosmtpd package is a recommended replacement for this module. It is based on asyncio and provides a more straightforward API. smtpd should be considered deprecated."

https://docs.python.org/3/library/smtpd.html

[vstinner]

So the first step is to decide if it's ok to remove smtpd right now.

[iritkatriel]

asyncore, asynchat and smtpd are all deprecated now, for removal in 3.12.

While the tests are not blocking their removal (we can move them to test.support) it would still be better to rewrite these tests.

[vstinner]

I forgot about this issue and I created a duplicate: bpo-45785. Copy of my messages.

I propose to remove asyncore, asynchat and smtpd modules from the Python standard library to remove the Python maintenance burden. These modules are deprecated since Python 3.6.

--

The asyncore module is a very old module of the Python stdlib for asynchronous programming, usually to handle network sockets concurrently. It's a common event loop, but its design has many flaws.

The asyncio module was added to Python 3.4 with a well designed architecture. Twisted developers who have like 10 to 20 years of experience in asynchronous programming helped to design the asyncio API.

By design, asyncio doesn't have flaws which would be really hard to fix in asyncore and asynchat.

It was decided to start deprecating the asyncore and asynchat module in Python 3.6 released in 2016, 5 years ago. Open issues in asyncore and asynchat have been closed as "wont fix" because the module is deprecated. The two modules are basically no longer maintained.

Documentation:

• https://docs.python.org/dev/library/asyncore.html
• https://docs.python.org/dev/library/asynchat.html

I propose to remove the two modules right now in the Python stdlib. They were removed for 4 Python releases (3.6-3.10), it's long enough to respect the PEP-387. The PEP requires 2 Python releases at least before considering removing code.

Since there are still 7 tests of the Python test suite still uses asyncore and asynchat, I propose to move these modules in Lib/test/ directory and make them private:

• Rename Lib/asyncore.py to Lib/test/support/_asyncore.py
• Rename Lib/asynchat.py to Lib/test/support/_asynchat.py

Projects using asyncore and asynchat should use asyncio. If someone really wants to continue using asyncore and asynchat, it's trivial to copy asyncore.py and asynchat.py in their project, and maintain these files on their side.

--

About the smtpd module, it is also deprecated since Python 3.6 (deprecated for 4 Python releases). It's used by a single test (test_logging). I also propose to remove it from the stdlib.

I proposed to rename Lib/smtpd.py to Lib/test/support/_smtpd.py.

Projects using smtpd can consider using aiosmtpd which is based on asyncio:
https://aiosmtpd.readthedocs.io/

Or again, they can copy Python 3.10 smtpd.py in their project and maintain this file on their side.

--

Ah, a DeprecationWarning warning is only emitted at runtime since Python 3.10. What's New in Python 3.10:

"asynchat, asyncore, smtpd: These modules have been marked as deprecated in their module documentation since Python 3.6. An import-time DeprecationWarning has now been added to all three of these modules."

https://docs.python.org/dev/whatsnew/3.10.html#asynchat-asyncore-smtpd

[vstinner]

I wrote PR 29521 to remove the asyncore, asynchat and smtpd modules.

libregrtest/save_env.py only checks that asyncore.socket_map is not modified, we can keep it until asyncore is really removed.

I chose to remove it instead of my PR.

test_support.py only tests that it's possible to have a "clean" import of asyncore, it can be easily be replaced later.

This code has been removed in the meanwhile.

But then a lot of code starts with to fail -Werror.

While tests using asyncore, asynchat and smtpd have been modified to catch the DeprecationWarning warning, I chose to remove this warning in my PR, since I made the 3 modules private. I don't think that test.support private modules must emit deprecation warnings.

So the first step is to decide if it's ok to remove smtpd right now.

IMO it's ok to remove it since it is deprecated since Python 3.6.

asyncore, asynchat and smtpd are all deprecated now, for removal in 3.12.

Did you see an explicit mention of Python 3.12? I only saw mention of "Python 3.6" which is the version when the 3 modules were deprecated.

[vstinner]

Since Christian Heimes decided to mark my issue bpo-45785 "Remove asyncore, asynchat and smtpd modules" as a duplicate of this issue, I changed this issue title to "Remove asyncore, asynchat and smtpd modules".

[vstinner]

I announced my plan to remove the 3 modules on python-dev:
https://mail.python.org/archives/list/python-dev@python.org/thread/LZOOLX5EKOITW55TW7JQYKLXJUPCAJB4/

[vstinner]

Reported upstream (it's a single file, used for tests): ansible/ansible#76452

Oh, I reported the issue to the wrong GitHub project. I reported it again at: ansible-collections/community.general#4656

[vstinner]

mercurial-6.0

I notified the project upstream: https://bz.mercurial-scm.org/show_bug.cgi?id=6700

[Karlson2k]

The suggested stmpd replacement supports Python versions up to 3.9. Python 3.10 and later is not supported.
There is no single commit in the past 14 months in the repo.

[warsaw]

True, but it's still the most viable replacement for smtpd. It needs a full-time steward though.

[iritkatriel]

Follow-up: PEP 594 has been accepted and asyncore, asynchat and smtpd are set for removal in 3.12.

Merged documentation PRs:

• bpo-47022: Document asynchat, asyncore and smtpd removals in 3.12 #31891
• bpo-47061: document module deprecations due to PEP 594 #31984

Pending removal PR:

• bpo-42611: PEP 594 - Remove asyncore, asynchat, and smptd from stdlib #23728

Newer removal PR that was merged...

• bpo-28533: Remove asyncore, asynchat, smtpd modules #29521

And reverted:

• Revert "bpo-28533: Remove asyncore, asynchat, smtpd modules (GH-29521)" #29951

We should be able to un-revert this now.

[gvanrossum]

I propose to remove the expert-asyncio label from this issue. Any objections? This doesn't require an asyncio expert at all, it's just documentation and removals (or deprecations?).

[iritkatriel]

I think that was referring to tests that need to be rewritten with asyncio. The alternative is to move these modules (or parts of them) to test.support so the tests continue to work.

[gvanrossum]

I think that was referring to tests that need to be rewritten with asyncio. The alternative is to move these modules (or parts of them) to test.support so the tests continue to work.

That still doesn't require pinging the asyncio experts, IMO (and my opinion counts since I'm the only active one :-). I'll remove the label.

[vstinner]

The alternative is to move these modules (or parts of them) to test.support so the tests continue to work.

IMO that's a convenient way to unblock the issue. Moving away from asyncore/asynchat would be nice but nobody managed to update tests in 10 years, so maybe it's ok to not changed them until it becomes a major (blocking) issue :-)

[sobolevn]

I've moved these modules to test/support as @iritkatriel and @vstinner proposed.
For now, they were coppied as-is (probably some parts are unused, but this is a subject to another piece of work).

Tests do continue to pass! 🎉

[vstinner]

asyncore, asynchat, smtpd are removed again in the main branch (future Python 3.12). Let's see how it goes this time.

Summary of this issue.

The asyncore/asynchat deprecation has a long history starting in 2015: https://bugs.python.org/issue25002

In 2020, Kyle Stanley @aeros worked on the removal in a branch: https://github.com/aeros/cpython/tree/remove-asycore-asynchat-smtpd

In 2021, I already removed the 3 modules (asyncore, asynchat, smtpd) in Python 3.11, but the Steering Council asked me to revert it since these modules only emitted a DeprecationWarning in 1 Python release (Python 3.10):

• PR: bpo-28533: Remove asyncore, asynchat, smtpd modules #29521 (approved by 5 core devs)
• commit: 9bf2cbc
• I announced the removal on python-dev
• In December 2021, 21 projects of PyPI top 5000 projects used these 3 removed modules
• Brett Cannon wrote on python-dev that "the modules got yanked prematurely", the removal didn't follow PEP 387 process (updated to require a deprecation in at least 2 Python versions, rather than 1).
• I formally requested a SC exception: python/steering-council#86
• SC rejected my exception
• I created PR Revert "bpo-28533: Remove asyncore, asynchat, smtpd modules (GH-29521)" #29951 to revert my removal

After my revert, I notified Mercurial and Ansible that these 3 projects are deprecated since 2015.

In 2022, these modules are removed again in Python 3.12:

• smtpd: PR gh-93243: Make smtpd private before porting its users #93246 and commit 56d16e8
• asyncore, asynchat: PR gh-72719: Remove deprecated asyncore and asynchat modules #96580 and commit e56e33d

The removal is now covered by PEP 594 which has been approved the SC.

You can now help the remaining projects still using the removed projects to be upgrade to asyncio and aiosmptd. People can also collaborate to maintain the 3 removed modules outside Python (on PyPI) if they want. Just copy code, tests and doc from Python 3.11.