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duplicate SyntaxWarning: "is" with a literal #79979

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jwilk mannequin opened this issue Jan 21, 2019 · 7 comments
Closed

duplicate SyntaxWarning: "is" with a literal #79979

jwilk mannequin opened this issue Jan 21, 2019 · 7 comments
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3.8 only security fixes interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error

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@jwilk
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jwilk mannequin commented Jan 21, 2019

BPO 35798
Nosy @terryjreedy, @vstinner, @jwilk, @serhiy-storchaka, @kakshay21
PRs
  • bpo-35798: Fix duplicate SyntaxWarning: "is" with a literal. #11639
  • bpo-35798: Fix duplicate SyntaxWarning: "is" with a literal. #11639
  • bpo-35798: Fix duplicate SyntaxWarning: "is" with a literal. #11639
  • bpo-35798: Remove redundant warning #11642
  • bpo-35798: Remove redundant warning #11642
  • bpo-35798: Remove redundant warning #11642
  • bpo-35798: Add test.support.check_syntax_warning(). #11895
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    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 2019-02-19.06:48:16.577>
created_at = <Date 2019-01-21.15:13:45.389>
labels = ['interpreter-core', 'type-bug', '3.8']
title = 'duplicate SyntaxWarning: "is" with a literal'
updated_at = <Date 2019-02-19.06:48:16.576>
user = 'https://github.com/jwilk'

    bugs.python.org fields:

    activity = <Date 2019-02-19.06:48:16.576>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2019-02-19.06:48:16.577>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2019-01-21.15:13:45.389>
creator = 'jwilk'
dependencies = []
files = []
hgrepos = []
issue_num = 35798
keywords = ['patch', 'patch', 'patch']
message_count = 7.0
messages = ['334143', '334144', '334169', '334366', '335670', '335671', '335891']
nosy_count = 5.0
nosy_names = ['terry.reedy', 'vstinner', 'jwilk', 'serhiy.storchaka', 'kakshay']
pr_nums = ['11639', '11639', '11639', '11642', '11642', '11642', '11895']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue35798'
versions = ['Python 3.8']
    @jwilk
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    jwilk mannequin commented Jan 21, 2019 

    $ python3.8 -c 'if object() is 42: pass'
<string>:1: SyntaxWarning: "is" with a literal. Did you mean "=="?
<string>:1: SyntaxWarning: "is" with a literal. Did you mean "=="?

    I'd like only one copy of this warning, not two.

    Tested with git master (e9b185f).

    @jwilk jwilk mannequin added 3.8 only security fixes interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error labels Jan 21, 2019
    @vstinner
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    The warning has been introduced by bpo-34850: commit 3bcbedc.

    @kakshay21
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    kakshay21 mannequin commented Jan 21, 2019

    can I work on this?

    @terryjreedy
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    I verified that master on Windows (which requires " instead of ')

    python -c "if object() is 42: pass"
    results in the doubled messsage, and that after applying PR 11639 and recompiling, there is only 1 message.

    We should test that exactly 1 warning is emitted. The following fails on master and passes with the parch:

    import unittest, warnings

class SyntaxWarningTest(unittest.TestCase):
    def test_syntax_warning_once(self):
        with warnings.catch_warnings(record=True) as w:
            warnings.simplefilter("always")
            compile('if object() is 42: pass\n', '', 'single')
            self.assertEqual(len(w), 1)  # Not 2, see issue 35798

if __name__ == '__main__':
    unittest.main()
    
The original patch added test_comparison_is_literal() in test_grammar.  The 'with' block above could be added at the end.

    @serhiy-storchaka
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    This warning is not special. I'll add a helper for testing that all syntax warnings are emitted only once later.

    @serhiy-storchaka
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    New changeset 4583525 by Serhiy Storchaka in branch 'master':
    bpo-35798: Fix duplicate SyntaxWarning: "is" with a literal. (GH-11639)
    4583525

    @serhiy-storchaka
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    New changeset e7a4bb5 by Serhiy Storchaka in branch 'master':
    bpo-35798: Add test.support.check_syntax_warning(). (bpo-11895)
    e7a4bb5

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