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73 lines
2.3 KiB
Python
73 lines
2.3 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (c) 2016 Alexander Todorov <atodorov@otb.bg>
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# Copyright (c) 2017 Claudiu Popa <pcmanticore@gmail.com>
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# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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# For details: https://github.com/PyCQA/pylint/blob/master/COPYING
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"""Looks for comparisons to empty string."""
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import itertools
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import astroid
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from pylint import interfaces
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from pylint import checkers
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from pylint.checkers import utils
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def _is_constant_zero(node):
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return isinstance(node, astroid.Const) and node.value == 0
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class CompareToZeroChecker(checkers.BaseChecker):
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"""Checks for comparisons to zero.
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Most of the times you should use the fact that integers with a value of 0 are false.
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An exception to this rule is when 0 is allowed in the program and has a
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different meaning than None!
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"""
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__implements__ = (interfaces.IAstroidChecker,)
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# configuration section name
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name = 'compare-to-zero'
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msgs = {'C2001': ('Avoid comparisons to zero',
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'compare-to-zero',
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'Used when Pylint detects comparison to a 0 constant.'),
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}
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priority = -2
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options = ()
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@utils.check_messages('compare-to-zero')
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def visit_compare(self, node):
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_operators = ['!=', '==', 'is not', 'is']
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# note: astroid.Compare has the left most operand in node.left
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# while the rest are a list of tuples in node.ops
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# the format of the tuple is ('compare operator sign', node)
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# here we squash everything into `ops` to make it easier for processing later
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ops = [('', node.left)]
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ops.extend(node.ops)
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ops = list(itertools.chain(*ops))
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for ops_idx in range(len(ops) - 2):
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op_1 = ops[ops_idx]
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op_2 = ops[ops_idx + 1]
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op_3 = ops[ops_idx + 2]
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error_detected = False
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# 0 ?? X
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if _is_constant_zero(op_1) and op_2 in _operators + ['<']:
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error_detected = True
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# X ?? 0
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elif op_2 in _operators + ['>'] and _is_constant_zero(op_3):
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error_detected = True
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if error_detected:
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self.add_message('compare-to-zero', node=node)
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def register(linter):
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"""Required method to auto register this checker."""
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linter.register_checker(CompareToZeroChecker(linter))
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