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lrucache should reject maxsize as a function #66380

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jaraco opened this issue Aug 11, 2014 · 4 comments
Closed

lrucache should reject maxsize as a function #66380

jaraco opened this issue Aug 11, 2014 · 4 comments
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@rhettinger
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stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@jaraco
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jaraco commented Aug 11, 2014

BPO 22184
Nosy @rhettinger, @jaraco, @jwilk, @serhiy-storchaka
Files
  • lru.diff: Add type check for maxsize
    		•

    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/rhettinger'
closed_at = <Date 2014-08-12.19:46:12.034>
created_at = <Date 2014-08-11.19:53:01.665>
labels = ['type-bug', 'library']
title = 'lrucache should reject maxsize as a function'
updated_at = <Date 2014-08-13.04:59:43.682>
user = 'https://github.com/jaraco'

    bugs.python.org fields:

    activity = <Date 2014-08-13.04:59:43.682>
actor = 'rhettinger'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2014-08-12.19:46:12.034>
closer = 'rhettinger'
components = ['Library (Lib)']
creation = <Date 2014-08-11.19:53:01.665>
creator = 'jaraco'
dependencies = []
files = ['36355']
hgrepos = []
issue_num = 22184
keywords = ['patch']
message_count = 4.0
messages = ['225202', '225241', '225251', '225254']
nosy_count = 5.0
nosy_names = ['rhettinger', 'jaraco', 'jwilk', 'python-dev', 'serhiy.storchaka']
pr_nums = []
priority = 'low'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue22184'
versions = ['Python 3.4', 'Python 3.5']
    @jaraco
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    jaraco commented Aug 11, 2014

    In https://bitbucket.org/jaraco/backports.functools_lru_cache/issue/1/python-2-attributeerror-int-object-has-no, a user was confused when he tried to use the lrucache decorator incorrectly, passing the wrapped function directly to lrucache. Consider:

        @lrucache
    def expensive(param):
        pass

    One can even get away with profiling that now decorated function:

        for x in range(10000):
        expensive(x)

    The test will run without error, but it's not doing what the user thinks it's doing. In the first section, it's creating a decorator, and in the second section, it's wrapping an int in that decorator, but because the wrapper is never called, an error is never raised.

    I propose adding a simple check that if maxsize is callable, raise a TypeError. That would prevent unintentional misuse and subtle non-failure with minimal impact on performance.

    @jaraco jaraco added the stdlib Python modules in the Lib dir label Aug 11, 2014
    @rhettinger rhettinger self-assigned this Aug 12, 2014
    @rhettinger rhettinger added the type-bug An unexpected behavior, bug, or error label Aug 12, 2014
    @python-dev
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    python-dev mannequin commented Aug 12, 2014

    New changeset 780693490c84 by Raymond Hettinger in branch '3.4':
    bpo-22184: Early detection and reporting of missing lru_cache parameters
    http://hg.python.org/cpython/rev/780693490c84

    @jaraco
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    jaraco commented Aug 13, 2014

    Awesome. Thanks for the quick implementation.

    @rhettinger
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    Awesome. Thanks for the quick implementation.

    Happy to do it. Thanks for the clean bug report.

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

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