WeakValueDictionary constructor ported to Python 3.0 incorrectly

[zzzeek]

BPO	6149
Nosy	@pitrou
Files	issue6149.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 = None
closed_at = <Date 2009-05-30.21:05:29.555>
created_at = <Date 2009-05-30.20:07:41.981>
labels = ['library', 'type-crash']
title = 'WeakValueDictionary constructor ported to Python 3.0 incorrectly'
updated_at = <Date 2009-05-30.21:05:29.554>
user = 'https://bugs.python.org/zzzeek'

bugs.python.org fields:

activity = <Date 2009-05-30.21:05:29.554>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2009-05-30.21:05:29.555>
closer = 'pitrou'
components = ['Library (Lib)']
creation = <Date 2009-05-30.20:07:41.981>
creator = 'zzzeek'
dependencies = []
files = ['14121']
hgrepos = []
issue_num = 6149
keywords = ['patch']
message_count = 3.0
messages = ['88577', '88578', '88581']
nosy_count = 2.0
nosy_names = ['pitrou', 'zzzeek']
pr_nums = []
priority = 'high'
resolution = 'fixed'
stage = 'patch review'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue6149'
versions = ['Python 3.1']

[zzzeek]

The constructor for WeakValueDictionary does not obey the contract
documented in its comments:

# We inherit the constructor without worrying about the input
# dictionary; since it uses our .update() method, we get the right
# checks 

yet it initializes with:

   self.data = d = {}
   d.update(*args, **kw)

i.e. the "update()" method of dict, so that a dict passed to the
constructor initializes non-weakrefed values in the dict which is
completely invalid state.

Contrast to that of 2.6, which properly uses the superclass:

UserDict.UserDict.__init__(self, *args, **kw)

A simple test which raises an exception on 3.0.1 is as follows:

import weakref

class Foo(object):
    pass
    
mydict = dict((k, Foo()) for k in range(10))

w = weakref.WeakValueDictionary(mydict)

assert w[5]

[pitrou]

Here is a patch for 3.1.

[pitrou]

Fixed in r73063. Thanks!