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EDIT :: magic_value.py

# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html # For details: https://github.com/PyCQA/pylint/blob/main/LICENSE # Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt """Checks for magic values instead of literals.""" from __future__ import annotations from re import match as regex_match from typing import TYPE_CHECKING from astroid import nodes from pylint.checkers import BaseChecker, utils from pylint.interfaces import HIGH if TYPE_CHECKING: from pylint.lint import PyLinter class MagicValueChecker(BaseChecker): """Checks for constants in comparisons.""" name = "magic-value" msgs = { "R2004": ( "Consider using a named constant or an enum instead of '%s'.", "magic-value-comparison", "Using named constants instead of magic values helps improve readability and maintainability of your" " code, try to avoid them in comparisons.", ) } options = ( ( "valid-magic-values", { "default": (0, -1, 1, "", "__main__"), "type": "csv", "metavar": "<argument names>", "help": "List of valid magic values that `magic-value-compare` will not detect. " "Supports integers, floats, negative numbers, for empty string enter ``''``," " for backslash values just use one backslash e.g \\n.", }, ), ) def __init__(self, linter: PyLinter) -> None: """Initialize checker instance.""" super().__init__(linter=linter) self.valid_magic_vals: tuple[float | str, ...] = () def open(self) -> None: # Extra manipulation is needed in case of using external configuration like an rcfile if self._magic_vals_ext_configured(): self.valid_magic_vals = tuple( self._parse_rcfile_magic_numbers(value) for value in self.linter.config.valid_magic_values ) else: self.valid_magic_vals = self.linter.config.valid_magic_values def _magic_vals_ext_configured(self) -> bool: return not isinstance(self.linter.config.valid_magic_values, tuple) def _check_constants_comparison(self, node: nodes.Compare) -> None: """ Magic values in any side of the comparison should be avoided, Detects comparisons that `comparison-of-constants` core checker cannot detect. """ const_operands = [] LEFT_OPERAND = 0 RIGHT_OPERAND = 1 left_operand = node.left const_operands.append(isinstance(left_operand, nodes.Const)) right_operand = node.ops[0][1] const_operands.append(isinstance(right_operand, nodes.Const)) if all(const_operands): # `comparison-of-constants` avoided return operand_value = None if const_operands[LEFT_OPERAND] and self._is_magic_value(left_operand): operand_value = left_operand.value elif const_operands[RIGHT_OPERAND] and self._is_magic_value(right_operand): operand_value = right_operand.value if operand_value is not None: self.add_message( "magic-value-comparison", node=node, args=(operand_value), confidence=HIGH, ) def _is_magic_value(self, node: nodes.Const) -> bool: return (not utils.is_singleton_const(node)) and ( node.value not in (self.valid_magic_vals) ) @staticmethod def _parse_rcfile_magic_numbers(parsed_val: str) -> float | str: parsed_val = parsed_val.encode().decode("unicode_escape") if parsed_val.startswith("'") and parsed_val.endswith("'"): return parsed_val[1:-1] is_number = regex_match(r"[-+]?\d+(\.0*)?$", parsed_val) return float(parsed_val) if is_number else parsed_val @utils.only_required_for_messages("magic-comparison") def visit_compare(self, node: nodes.Compare) -> None: self._check_constants_comparison(node) def register(linter: PyLinter) -> None: linter.register_checker(MagicValueChecker(linter))

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