72 lines
2.4 KiB
Python
72 lines
2.4 KiB
Python
|
# -*- coding: utf-8 -*-
|
||
|
|
# Copyright (c) 2016 Alexander Todorov <atodorov@MrSenko.com>
|
||
|
|
|
||
|
|
# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
|
||
|
|
# For details: https://github.com/PyCQA/pylint/blob/master/COPYING
|
||
|
|
|
||
|
|
"""Looks for comparisons to empty string."""
|
||
|
|
|
||
|
|
import itertools
|
||
|
|
|
||
|
|
import astroid
|
||
|
|
|
||
|
|
from pylint import interfaces
|
||
|
|
from pylint import checkers
|
||
|
|
from pylint.checkers import utils
|
||
|
|
|
||
|
|
|
||
|
|
def _is_constant_empty_str(node):
|
||
|
|
return isinstance(node, astroid.Const) and node.value == ''
|
||
|
|
|
||
|
|
|
||
|
|
class CompareToEmptyStringChecker(checkers.BaseChecker):
|
||
|
|
"""Checks for comparisons to empty string.
|
||
|
|
Most of the times you should use the fact that empty strings are false.
|
||
|
|
An exception to this rule is when an empty string value is allowed in the program
|
||
|
|
and has a different meaning than None!
|
||
|
|
"""
|
||
|
|
|
||
|
|
__implements__ = (interfaces.IAstroidChecker,)
|
||
|
|
|
||
|
|
# configuration section name
|
||
|
|
name = 'compare-to-empty-string'
|
||
|
|
msgs = {'C1901': ('Avoid comparisons to empty string',
|
||
|
|
'compare-to-empty-string',
|
||
|
|
'Used when Pylint detects comparison to an empty string constant.'),
|
||
|
|
}
|
||
|
|
|
||
|
|
priority = -2
|
||
|
|
options = ()
|
||
|
|
|
||
|
|
@utils.check_messages('compare-to-empty-string')
|
||
|
|
def visit_compare(self, node):
|
||
|
|
_operators = ['!=', '==', 'is not', 'is']
|
||
|
|
# note: astroid.Compare has the left most operand in node.left
|
||
|
|
# while the rest are a list of tuples in node.ops
|
||
|
|
# the format of the tuple is ('compare operator sign', node)
|
||
|
|
# here we squash everything into `ops` to make it easier for processing later
|
||
|
|
ops = [('', node.left)]
|
||
|
|
ops.extend(node.ops)
|
||
|
|
ops = list(itertools.chain(*ops))
|
||
|
|
|
||
|
|
for ops_idx in range(len(ops) - 2):
|
||
|
|
op_1 = ops[ops_idx]
|
||
|
|
op_2 = ops[ops_idx + 1]
|
||
|
|
op_3 = ops[ops_idx + 2]
|
||
|
|
error_detected = False
|
||
|
|
|
||
|
|
# x ?? ""
|
||
|
|
if _is_constant_empty_str(op_1) and op_2 in _operators:
|
||
|
|
error_detected = True
|
||
|
|
# '' ?? X
|
||
|
|
elif op_2 in _operators and _is_constant_empty_str(op_3):
|
||
|
|
error_detected = True
|
||
|
|
|
||
|
|
if error_detected:
|
||
|
|
self.add_message('compare-to-empty-string', node=node)
|
||
|
|
|
||
|
|
|
||
|
|
def register(linter):
|
||
|
|
"""Required method to auto register this checker."""
|
||
|
|
linter.register_checker(CompareToEmptyStringChecker(linter))
|