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Argument names in __annotations__ are not mangled for functions defined inside class scope #64824

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jonasw mannequin opened this issue Feb 14, 2014 · 12 comments
Closed

Argument names in __annotations__ are not mangled for functions defined inside class scope #64824

jonasw mannequin opened this issue Feb 14, 2014 · 12 comments
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@1st1
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interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error

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@jonasw
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jonasw mannequin commented Feb 14, 2014

BPO 20625
Nosy @ncoghlan, @larryhastings, @benjaminp, @merwok, @1st1
Files
  • issue_20625_01.patch
  • issue_20625_02.patch
    		•

    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 = 'https://github.com/1st1'
closed_at = <Date 2014-02-18.17:56:03.804>
created_at = <Date 2014-02-14.11:57:28.716>
labels = ['interpreter-core', 'type-bug']
title = 'Argument names in __annotations__ are not mangled for functions defined inside class scope'
updated_at = <Date 2014-03-17.06:31:02.344>
user = 'https://bugs.python.org/jonasw'

    bugs.python.org fields:

    activity = <Date 2014-03-17.06:31:02.344>
actor = 'python-dev'
assignee = 'yselivanov'
closed = True
closed_date = <Date 2014-02-18.17:56:03.804>
closer = 'yselivanov'
components = ['Interpreter Core']
creation = <Date 2014-02-14.11:57:28.716>
creator = 'jonasw'
dependencies = []
files = ['34083', '34085']
hgrepos = []
issue_num = 20625
keywords = ['patch']
message_count = 12.0
messages = ['211215', '211231', '211234', '211237', '211242', '211243', '211244', '211248', '211531', '211556', '211671', '213822']
nosy_count = 9.0
nosy_names = ['nnorwitz', 'ncoghlan', 'larry', 'benjamin.peterson', 'eric.araujo', 'Arfrever', 'python-dev', 'yselivanov', 'jonasw']
pr_nums = []
priority = 'high'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue20625'
versions = ['Python 3.3', 'Python 3.4']
    @jonasw
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    jonasw mannequin commented Feb 14, 2014

    Assume I have this code:

    class Spam:
    def eggs(__some_kwarg:int=None):
        print(__some_kwarg)

    I can call Spam.bar with keyword arguments as expected from mangling:

    >>> Spam.eggs(10)
10
>>> Spam.eggs(_Spam__some_kwarg=10)
10

    However, in the __annotations__ field, the argument name is not mangled:

    >>> Spam.eggs.__annotations__
{'__some_kwarg': <class 'int'>}

    This is an inconsistency which makes it difficult to work with function annotations in this case.

    @jonasw jonasw mannequin added interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error labels Feb 14, 2014
    @1st1
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    1st1 commented Feb 14, 2014

    It looks like it's a bug.

    Spam.eggs.__code__.co_varnames will have '_Spam__some_kwarg' as a name of the first parameter. So __annotations__ should have '_Spam__some_kwarg' instead of '__some_kwarg'.

    @1st1
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    1st1 commented Feb 14, 2014

    Furthermore:

    class Foo:
  def bar(self, *, __kw:'anno'='default'):
    pass
    >>> Foo.bar.__annotations__
{'__kw': 'anno'}
>>> Foo.bar.__kwdefaults__
{'_Foo__kw': 'default'}

    @1st1
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    1st1 commented Feb 14, 2014

    Patch is attached. Please review.

    @larryhastings
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    Why would we mangle the names of arguments in the first place? What possible use case is there?

    @1st1
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    1st1 commented Feb 14, 2014

    Why would we mangle the names of arguments in the first place? What possible use case is there?

    The use case is multiple inheritance. You can define your methods with keyword and keyword-only params starting with '__', put in them some cached default for speeding up lookup time, and not being worried that someone can override the arg. The second reason is, I believe, is desire to be consistent with mangling methods and attributes.

    Again, using mangling for function arguments is, probably, not the best practice, and that, combined with the fact, that people are just starting to play with annotations, explains why this bug was so long unnoticed.

    But the semantics of arg names mangling is already there, implemented everywhere but __annotations__.

    The attached patch is fairly simple, and really is just a bug fix. It would be great if we can get this in 3.4 (and even in 3.3 and 3.2).

    @benjaminp
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    (see review on rietveld)

    @benjaminp
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    lgtm

    @python-dev
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    python-dev mannequin commented Feb 18, 2014

    New changeset a63327162063 by Yury Selivanov in branch 'default':
    Mangle __parameters in __annotations__ dict properly. Issue bpo-20625.
    http://hg.python.org/cpython/rev/a63327162063

    @1st1 1st1 closed this as completed Feb 18, 2014
    @1st1 1st1 self-assigned this Feb 18, 2014
    @python-dev
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    python-dev mannequin commented Feb 18, 2014

    New changeset 5202aca8a673 by Victor Stinner in branch 'default':
    Issue bpo-20625: Fix compilation issue
    http://hg.python.org/cpython/rev/5202aca8a673

    @python-dev
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    python-dev mannequin commented Feb 19, 2014

    New changeset e301a515f8f4 by Benjamin Peterson in branch 'default':
    update magic number for bpo-20625
    http://hg.python.org/cpython/rev/e301a515f8f4

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    python-dev mannequin commented Mar 17, 2014

    New changeset 4d7c3cbd8515 by Yury Selivanov in branch '3.4':
    Mangle __parameters in __annotations__ dict properly. Issue bpo-20625.
    http://hg.python.org/cpython/rev/4d7c3cbd8515

    New changeset 3bced76d2706 by Victor Stinner in branch '3.4':
    Issue bpo-20625: Fix compilation issue
    http://hg.python.org/cpython/rev/3bced76d2706

    New changeset e5cde3fd7c74 by Benjamin Peterson in branch '3.4':
    update magic number for bpo-20625
    http://hg.python.org/cpython/rev/e5cde3fd7c74

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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