73 lines
1.5 KiB
Python
73 lines
1.5 KiB
Python
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#!/usr/bin/env python3
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#
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# Copyright (c) 2019-2022 The Moneyrocket Core developers
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# Distributed under the MIT software license, see the accompanying
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# file COPYING or http://www.opensource.org/licenses/mit-license.php.
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"""
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Detect when a mutable list or dict is used as a default parameter value in a Python function.
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"""
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import subprocess
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import sys
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def main():
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command = [
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"git",
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"grep",
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"-E",
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r"^\s*def [a-zA-Z0-9_]+\(.*=\s*(\[|\{)",
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"--",
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"*.py",
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]
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output = subprocess.run(command, stdout=subprocess.PIPE, text=True)
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if len(output.stdout) > 0:
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error_msg = (
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"A mutable list or dict seems to be used as default parameter value:\n\n"
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f"{output.stdout}\n"
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f"{example()}"
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)
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print(error_msg)
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sys.exit(1)
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else:
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sys.exit(0)
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def example():
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return """This is how mutable list and dict default parameter values behave:
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>>> def f(i, j=[], k={}):
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... j.append(i)
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... k[i] = True
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... return j, k
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...
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>>> f(1)
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([1], {1: True})
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>>> f(1)
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([1, 1], {1: True})
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>>> f(2)
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([1, 1, 2], {1: True, 2: True})
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The intended behaviour was likely:
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>>> def f(i, j=None, k=None):
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... if j is None:
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... j = []
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... if k is None:
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... k = {}
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... j.append(i)
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... k[i] = True
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... return j, k
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...
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>>> f(1)
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([1], {1: True})
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>>> f(1)
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([1], {1: True})
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>>> f(2)
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([2], {2: True})"""
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if __name__ == "__main__":
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main()
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