inspect: Deprecate getfullargspec?

[1st1]

BPO	20438
Nosy	@brettcannon, @ncoghlan, @larryhastings, @nedbat, @bitdancer, @berkerpeksag, @1st1, @matrixise, @vedgar, @untitaker, @hugovk
PRs	bpo-28814: Undeprecate inadvertantly deprecated inspect function. #122 [3.6] bpo-28814: Undeprecate inadvertently deprecated inspect functions. (#122) #243 [3.5] bpo-28814: Undeprecate inadvertently deprecated inspect functions. (#122) #244 bpo-45320 Remove deprecated inspect methods #28618
Dependencies	bpo-25486: Resurrect inspect.getargspec() in 3.6
Files	issue20438_deprecate_inspect-getfullargspec.patch issue20438_deprecate_inspect_getfullargspec-2.patch getargspec.diff

^{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 2015-05-22.15:39:20.106>
created_at = <Date 2014-01-29.17:00:12.946>
labels = ['type-feature']
title = 'inspect: Deprecate getfullargspec?'
updated_at = <Date 2021-09-29.12:48:03.923>
user = 'https://github.com/1st1'

bugs.python.org fields:

activity = <Date 2021-09-29.12:48:03.923>
actor = 'hugovk'
assignee = 'none'
closed = True
closed_date = <Date 2015-05-22.15:39:20.106>
closer = 'yselivanov'
components = []
creation = <Date 2014-01-29.17:00:12.946>
creator = 'yselivanov'
dependencies = ['25486']
files = ['34877', '34890', '39459']
hgrepos = []
issue_num = 20438
keywords = ['patch']
message_count = 40.0
messages = ['209658', '209664', '209665', '209692', '216317', '216318', '216327', '216328', '216333', '216337', '216339', '216340', '216341', '216342', '216365', '216385', '216387', '216621', '217581', '243777', '243835', '243848', '243850', '243851', '243852', '243853', '250805', '250808', '253434', '253436', '253473', '253475', '253500', '253501', '254892', '254899', '282173', '288334', '290422', '290425']
nosy_count = 12.0
nosy_names = ['brett.cannon', 'ncoghlan', 'larry', 'nedbat', 'r.david.murray', 'python-dev', 'berker.peksag', 'yselivanov', 'matrixise', 'veky', 'untitaker', 'hugovk']
pr_nums = ['122', '243', '244', '28618']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue20438'
versions = ['Python 3.5']

[1st1]

Should we finally deprecate getfullargspec? With the AC and positional-only parameters support, getfullargspec doesn't provide full information anymore.

By deprecation I mean changing its existing note "Consider using the new Signature Object interface, which provides a better way of introspecting functions." to "Deprecated since version 3.4: Use inspect.signature() instead".

[brettcannon]

I vote deprecation with no stated plans of removal

[brettcannon]

Although I say do it in 3.5.

[ncoghlan]

As Brett said - let's do a documented deprecation in 3.5.

[matrixise]

In this patch, I deprecate the inspect.getfullargspec function in the documentation and raise an warnings.warn with DeprecationWarning.

Need feedback, because the inspect.getargspec() informs the user that it can use the getfullargspec() and I think we should use inspect.signature instead of inspect.getfullargspec() and inspect.getargspec().

Thank you

[matrixise]

Here is the output of my test:

./python3.5 -Wd test.py
test.py:9: DeprecationWarning: Deprecated
warnings.warn('Deprecated', DeprecationWarning)

/private/tmp/python/lib/python3.5/inspect.py:955: DeprecationWarning: Use inspect.signature() instead of inspect.getfullargspec()
warnings.warn("Use inspect.signature() instead of inspect.getfullargspec()", DeprecationWarning)
FullArgSpec(args=[], varargs='args', varkw='kwargs', defaults=None, kwonlyargs=[], kwonlydefaults=None, annotations={})

[brettcannon]

I was thinking about suggesting we don't code deprecate getfullargspec() but the function seems to be new to Python 3 and so that worry for Python 2/3 code is not founded.

[1st1]

How about we deprecate with a warning getfullargspec(); deprecate getargspec() in docs only (in 3.6 we'll fully deprecate all function parameters API except Signature)?

[matrixise]

Just one thing, how do you work for the deprecation?

1. you deprecate in the doc for 3.5?
2. you deprecate in the code for 3.6?
3. you remove the code in 3.7?

What's the strategy in this case or in general?

Thanks

[brettcannon]

How warnings are handled vary from case to case. Typically its documentation-only if we want to warn people that they shouldn't use something because there is a better alternative but the code is not fundamentally broken and its in Python 2. If there is something wrong with it or it's just in Python 3 then a deprecation warning with a decided amount of time for when the code will be removed.

[matrixise]

ok, so in this case, I can only change the documentation with a ".. deprecated:". But for the future, how can we know we have to deprecate this function for >= 3.6 ? Will you parse the documentation and check there is an deprecation to add in the code?

Or is there a file with the "future" deprecations?

Are you agree with the deprecation in the documentation?

[1st1]

I'd +1 for:

1. Deprecating getfullargsspec in docs;
2. Deprecating getargspec in docs and code (since it's an ancient and outdated API)

Brett?

[matrixise]

Brett,

If you agree with Yury, I will provide a patch with these tasks.

[brettcannon]

Since getfullargspec is new in Python 3 and inspect.signature fundamentally improves things in Python 3 due to Argument Clinic I would say go ahead and code deprecate getfullargspec (we can do a DeprecationWarning for 3.5 and 3.6 and remove in 3.7; people needing compatibility can just use getargspec). As for getargspec, it was already deprecated so just leave it deprecated and update its message to say to use inspect.signature.

As for keeping track of this stuff, Stéphane, as part of the test that makes sure the warning is raised, add to that test -- don't need a separate method -- some code that will fail if the function exists in Python 3.7 or later.