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