mirror of https://github.com/python/cpython
58 lines
1.7 KiB
Python
58 lines
1.7 KiB
Python
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#!/usr/bin/env python3.8
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"""Find the maximum amount of nesting for an expression that can be parsed
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without causing a parse error.
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Starting at the INITIAL_NESTING_DEPTH, an expression containing n parenthesis
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around a 0 is generated then tested with both the C and Python parsers. We
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continue incrementing the number of parenthesis by 10 until both parsers have
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failed. As soon as a single parser fails, we stop testing that parser.
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The grammar file, initial nesting size, and amount by which the nested size is
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incremented on each success can be controlled by changing the GRAMMAR_FILE,
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INITIAL_NESTING_DEPTH, or NESTED_INCR_AMT variables.
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Usage: python -m scripts.find_max_nesting
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"""
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import sys
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from _peg_parser import parse_string
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GRAMMAR_FILE = "data/python.gram"
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INITIAL_NESTING_DEPTH = 10
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NESTED_INCR_AMT = 10
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FAIL = "\033[91m"
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ENDC = "\033[0m"
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def check_nested_expr(nesting_depth: int) -> bool:
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expr = f"{'(' * nesting_depth}0{')' * nesting_depth}"
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try:
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parse_string(expr)
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print(f"Nesting depth of {nesting_depth} is successful")
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return True
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except Exception as err:
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print(f"{FAIL}(Failed with nesting depth of {nesting_depth}{ENDC}")
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print(f"{FAIL}\t{err}{ENDC}")
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return False
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def main() -> None:
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print(f"Testing {GRAMMAR_FILE} starting at nesting depth of {INITIAL_NESTING_DEPTH}...")
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nesting_depth = INITIAL_NESTING_DEPTH
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succeeded = True
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while succeeded:
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expr = f"{'(' * nesting_depth}0{')' * nesting_depth}"
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if succeeded:
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succeeded = check_nested_expr(nesting_depth)
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nesting_depth += NESTED_INCR_AMT
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sys.exit(1)
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if __name__ == "__main__":
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main()
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