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import astroid
from pylint.checkers import BaseTokenChecker
from pylint.checkers.utils import check_messages
from pylint.interfaces import ITokenChecker, IAstroidChecker
class ElseifUsedChecker(BaseTokenChecker):
"""Checks for use of "else if" when a "elif" could be used
"""
__implements__ = (ITokenChecker, IAstroidChecker)
name = 'elseifused'
msgs = {'R5501': ('Consider using "elif" instead of "else if"',
'else-if-used',
'Used when an else statement is immediately followed by '
'an if statement and does not contain statements that '
'would be unrelated to it.'),
}
def __init__(self, linter=None):
BaseTokenChecker.__init__(self, linter)
self._init()
def _init(self):
self._elifs = []
self._if_counter = 0
def _is_actual_elif(self, node):
"""Check if the given node is an actual elif
This is a problem we're having with the builtin ast module,
which splits `elif` branches into a separate if statement.
Unfortunately we need to know the exact type in certain
cases.
"""
if isinstance(node.parent, astroid.If):
orelse = node.parent.orelse
# current if node must directly follow a "else"
if orelse and orelse == [node]:
if self._elifs[self._if_counter]:
return True
return False
def process_tokens(self, tokens):
# Process tokens and look for 'if' or 'elif'
for _, token, _, _, _ in tokens:
self._elifs.append(True if token == 'elif' else False)
def leave_module(self, _):
self._init()
def visit_ifexp(self, _):
self._if_counter += 1
def visit_comprehension(self, node):
self._if_counter += len(node.ifs)
@check_messages('else-if-used')
def visit_if(self, node):
if isinstance(node.parent, astroid.If):
orelse = node.parent.orelse
# current if node must directly follow a "else"
if orelse and orelse == [node]:
if not self._elifs[self._if_counter]:
self.add_message('else-if-used', node=node)
self._if_counter += 1
def register(linter):
"""Required method to auto register this checker.
:param linter: Main interface object for Pylint plugins
:type linter: Pylint object
"""
linter.register_checker(ElseifUsedChecker(linter))
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