# Copyright 2012 Google Inc. # # http://www.logilab.fr/ -- mailto:contact@logilab.fr # This program is free software; you can redistribute it and/or modify it under # the terms of the GNU General Public License as published by the Free Software # Foundation; either version 2 of the License, or (at your option) any later # version. # # This program is distributed in the hope that it will be useful, but WITHOUT # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS # FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details # # You should have received a copy of the GNU General Public License along with # this program; if not, write to the Free Software Foundation, Inc., # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. """Checkers for various standard library functions.""" import six import sys import astroid from astroid.bases import Instance from pylint.interfaces import IAstroidChecker from pylint.checkers import BaseChecker from pylint.checkers import utils TYPECHECK_COMPARISON_OPERATORS = frozenset(('is', 'is not', '==', '!=', 'in', 'not in')) LITERAL_NODE_TYPES = (astroid.Const, astroid.Dict, astroid.List, astroid.Set) if sys.version_info >= (3, 0): OPEN_MODULE = '_io' TYPE_QNAME = 'builtins.type' else: OPEN_MODULE = '__builtin__' TYPE_QNAME = '__builtin__.type' def _check_mode_str(mode): # check type if not isinstance(mode, six.string_types): return False # check syntax modes = set(mode) _mode = "rwatb+U" creating = False if six.PY3: _mode += "x" creating = "x" in modes if modes - set(_mode) or len(mode) > len(modes): return False # check logic reading = "r" in modes writing = "w" in modes appending = "a" in modes text = "t" in modes binary = "b" in modes if "U" in modes: if writing or appending or creating and six.PY3: return False reading = True if not six.PY3: binary = True if text and binary: return False total = reading + writing + appending + (creating if six.PY3 else 0) if total > 1: return False if not (reading or writing or appending or creating and six.PY3): return False # other 2.x constraints if not six.PY3: if "U" in mode: mode = mode.replace("U", "") if "r" not in mode: mode = "r" + mode return mode[0] in ("r", "w", "a", "U") return True def _is_one_arg_pos_call(call): """Is this a call with exactly 1 argument, where that argument is positional? """ return (isinstance(call, astroid.CallFunc) and len(call.args) == 1 and not isinstance(call.args[0], astroid.Keyword)) class StdlibChecker(BaseChecker): __implements__ = (IAstroidChecker,) name = 'stdlib' msgs = { 'W1501': ('"%s" is not a valid mode for open.', 'bad-open-mode', 'Python supports: r, w, a[, x] modes with b, +, ' 'and U (only with r) options. ' 'See http://docs.python.org/2/library/functions.html#open'), 'W1502': ('Using datetime.time in a boolean context.', 'boolean-datetime', 'Using datetime.time in a boolean context can hide ' 'subtle bugs when the time they represent matches ' 'midnight UTC. This behaviour was fixed in Python 3.5. ' 'See http://bugs.python.org/issue13936 for reference.', {'maxversion': (3, 5)}), 'W1503': ('Redundant use of %s with constant ' 'value %r', 'redundant-unittest-assert', 'The first argument of assertTrue and assertFalse is ' 'a condition. If a constant is passed as parameter, that ' 'condition will be always true. In this case a warning ' 'should be emitted.'), 'W1504': ('Using type() instead of isinstance() for a typecheck.', 'unidiomatic-typecheck', 'The idiomatic way to perform an explicit typecheck in ' 'Python is to use isinstance(x, Y) rather than ' 'type(x) == Y, type(x) is Y. Though there are unusual ' 'situations where these give different results.') } @utils.check_messages('bad-open-mode', 'redundant-unittest-assert') def visit_callfunc(self, node): """Visit a CallFunc node.""" if hasattr(node, 'func'): infer = utils.safe_infer(node.func) if infer: if infer.root().name == OPEN_MODULE: if getattr(node.func, 'name', None) in ('open', 'file'): self._check_open_mode(node) if infer.root().name == 'unittest.case': self._check_redundant_assert(node, infer) @utils.check_messages('boolean-datetime') def visit_unaryop(self, node): if node.op == 'not': self._check_datetime(node.operand) @utils.check_messages('boolean-datetime') def visit_if(self, node): self._check_datetime(node.test) @utils.check_messages('boolean-datetime') def visit_ifexp(self, node): self._check_datetime(node.test) @utils.check_messages('boolean-datetime') def visit_boolop(self, node): for value in node.values: self._check_datetime(value) @utils.check_messages('unidiomatic-typecheck') def visit_compare(self, node): operator, right = node.ops[0] if operator in TYPECHECK_COMPARISON_OPERATORS: left = node.left if _is_one_arg_pos_call(left): self._check_type_x_is_y(node, left, operator, right) def _check_redundant_assert(self, node, infer): if (isinstance(infer, astroid.BoundMethod) and node.args and isinstance(node.args[0], astroid.Const) and infer.name in ['assertTrue', 'assertFalse']): self.add_message('redundant-unittest-assert', args=(infer.name, node.args[0].value, ), node=node) def _check_datetime(self, node): """ Check that a datetime was infered. If so, emit boolean-datetime warning. """ try: infered = next(node.infer()) except astroid.InferenceError: return if (isinstance(infered, Instance) and infered.qname() == 'datetime.time'): self.add_message('boolean-datetime', node=node) def _check_open_mode(self, node): """Check that the mode argument of an open or file call is valid.""" try: mode_arg = utils.get_argument_from_call(node, position=1, keyword='mode') except utils.NoSuchArgumentError: return if mode_arg: mode_arg = utils.safe_infer(mode_arg) if (isinstance(mode_arg, astroid.Const) and not _check_mode_str(mode_arg.value)): self.add_message('bad-open-mode', node=node, args=mode_arg.value) def _check_type_x_is_y(self, node, left, operator, right): """Check for expressions like type(x) == Y.""" left_func = utils.safe_infer(left.func) if not (isinstance(left_func, astroid.Class) and left_func.qname() == TYPE_QNAME): return if operator in ('is', 'is not') and _is_one_arg_pos_call(right): right_func = utils.safe_infer(right.func) if (isinstance(right_func, astroid.Class) and right_func.qname() == TYPE_QNAME): # type(x) == type(a) right_arg = utils.safe_infer(right.args[0]) if not isinstance(right_arg, LITERAL_NODE_TYPES): # not e.g. type(x) == type([]) return self.add_message('unidiomatic-typecheck', node=node) def register(linter): """required method to auto register this checker """ linter.register_checker(StdlibChecker(linter))