TypeError in smtpd module with string arguments

[lorenzoancora]

BPO	26209
Nosy	@terryjreedy, @giampaolo, @bitdancer, @berkerpeksag
Files	smtpd_doc_updated.patch: smtpd Server documentation updated smtpd_doc_updated_2.patch: smtpd patch 2 with review comments applied smtpd_doc_updated_3.patch: smtpd patch 3 with review comments applied

^{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 = <Date 2016-09-07.18:11:15.624>
created_at = <Date 2016-01-26.20:34:38.569>
labels = ['easy', 'type-feature', 'library', 'docs']
title = 'TypeError in smtpd module with string arguments'
updated_at = <Date 2016-09-07.18:11:15.622>
user = 'https://bugs.python.org/lorenzoancora'

bugs.python.org fields:

activity = <Date 2016-09-07.18:11:15.622>
actor = 'r.david.murray'
assignee = 'docs@python'
closed = True
closed_date = <Date 2016-09-07.18:11:15.624>
closer = 'r.david.murray'
components = ['Documentation', 'Library (Lib)']
creation = <Date 2016-01-26.20:34:38.569>
creator = 'lorenzo.ancora'
dependencies = []
files = ['44045', '44047', '44055']
hgrepos = []
issue_num = 26209
keywords = ['patch', 'easy']
message_count = 15.0
messages = ['258971', '259229', '259261', '259455', '259475', '259727', '259747', '259748', '259753', '272154', '272159', '272227', '274852', '274853', '274854']
nosy_count = 8.0
nosy_names = ['terry.reedy', 'giampaolo.rodola', 'r.david.murray', 'docs@python', 'python-dev', 'berker.peksag', 'lorenzo.ancora', 'rvallury']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue26209'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6']

[lorenzoancora]

smtpd.PureProxy(localaddr="host1", remoteaddr="host2")

...produces the error:

[...] smtpd.py", line 657, in __init__
gai_results = socket.getaddrinfo(*localaddr, type=socket.SOCK_STREAM)
TypeError: getaddrinfo() got multiple values for argument 'type'

The module only works with:

smtpd.PureProxy(localaddr=("host1", 25), remoteaddr=("host2", 25))

The documentation does not specify the format of the INPUT parameters, only the CLI syntax with hostnames as "host:port" strings.
The underlying library should convert them to tuples or at least the documentation should be completed.

[terryjreedy]

I am guessing that 25 is the default port. Autoconversion of 'host' to ('host', 25) would be a new feature ('enhancement') that would have to wait for the next Python version (3.6 or later). Is there any precedent for this in any other module?

Does 2.7 act the same as 3.5? A doc improvement could go there also.

[berkerpeksag]

There is a strong change that smtpd is going to be deprecated in Python 3.6. See bpo-25008 for details.

+1 for improving documentation.

[lorenzoancora]

(msg259229) Terry J. Reedy i Suggest that a standard and globally accepted scheme to manage IPv4 addresses is:

"Host:PortNumber" --> (host, PortNumber)
"Host" --> (host, DefaultPortNumber)
"IP:PortNumber" --> (host, PortNumber)
"IP" --> (host, DefaultPortNumber)

...where DefaultPortNumber is protocol and system dependent (IANA standard, see the SMTP line in: http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml).

A simple research reveals that all versions of the module are (sadly) poorly documented, but the module is an interface to a very important protocol that indeed must be offered by the standard library.
The only little suggestion in the documentation of the module is: https://docs.python.org/3.6/library/socket.html#socket.socket.accept
...from a one-word link in: https://docs.python.org/3.6/library/smtpd.html#smtpd.SMTPChannel.addr
Which has only an indirect relation with the object itself.

Many users may not recognize the cause of the error if the documentation doesn't explicitate the information to correctly initialize the core objects of the module.
I also Suggest that at least the object should return an helpful error in newer versions of Python.

Thank you for your efforts guys. :-)

[terryjreedy]

Doc fixes unrelated to security fixes are not applied to security-fix-only versions.

[lorenzoancora]

(msg259475) Terry J. Reedy thank you for the correction, I've confused the versions affected with the versions actually supported.
Since this doesn't only affect the documentation, is it correct to assign the issue to docs@python?
The expert index indicates giampaolo.rodola as the module maintainer, so he should be moved from the nosy list to the field "Assigned To" and docs@python should be in the nosy list.

Also, there is a documentation on how to send a patch for a specific module in Python 3.5?
I'd like to help by creating a new source code patch. :-)