stdlib.py

# -*- coding: utf-8 -*-
# Copyright (c) 2013-2014 LOGILAB S.A. (Paris, FRANCE) <contact@logilab.fr>
# Copyright (c) 2013-2014 Google, Inc.
# Copyright (c) 2014-2020 Claudiu Popa <pcmanticore@gmail.com>
# Copyright (c) 2014 Cosmin Poieana <cmin@ropython.org>
# Copyright (c) 2014 Vlad Temian <vladtemian@gmail.com>
# Copyright (c) 2014 Arun Persaud <arun@nubati.net>
# Copyright (c) 2015 Cezar <celnazli@bitdefender.com>
# Copyright (c) 2015 Chris Rebert <code@rebertia.com>
# Copyright (c) 2015 Ionel Cristian Maries <contact@ionelmc.ro>
# Copyright (c) 2016 Jared Garst <cultofjared@gmail.com>
# Copyright (c) 2017 Renat Galimov <renat2017@gmail.com>
# Copyright (c) 2017 Martin <MartinBasti@users.noreply.github.com>
# Copyright (c) 2017 Christopher Zurcher <zurcher@users.noreply.github.com>
# Copyright (c) 2017 Łukasz Rogalski <rogalski.91@gmail.com>
# Copyright (c) 2018 Lucas Cimon <lucas.cimon@gmail.com>
# Copyright (c) 2018 Banjamin Freeman <befreeman@users.noreply.github.com>
# Copyright (c) 2018 Ioana Tagirta <ioana.tagirta@gmail.com>
# Copyright (c) 2019 Julien Palard <julien@palard.fr>
# Copyright (c) 2019 laike9m <laike9m@users.noreply.github.com>
# Copyright (c) 2019 Hugo van Kemenade <hugovk@users.noreply.github.com>
# Copyright (c) 2019 Robert Schweizer <robert_schweizer@gmx.de>
# Copyright (c) 2019 fadedDexofan <fadedDexofan@gmail.com>
# Copyright (c) 2019 Pierre Sassoulas <pierre.sassoulas@gmail.com>
# Copyright (c) 2020 谭九鼎 <109224573@qq.com>
# Copyright (c) 2020 Anthony Sottile <asottile@umich.edu>

# 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

"""Checkers for various standard library functions."""

import sys

import astroid
from astroid.bases import Instance
from astroid.node_classes import Const

from pylint.checkers import BaseChecker, utils
from pylint.interfaces import IAstroidChecker

OPEN_FILES = {"open", "file"}
UNITTEST_CASE = "unittest.case"
THREADING_THREAD = "threading.Thread"
COPY_COPY = "copy.copy"
OS_ENVIRON = "os._Environ"
ENV_GETTERS = {"os.getenv"}
SUBPROCESS_POPEN = "subprocess.Popen"
SUBPROCESS_RUN = "subprocess.run"
OPEN_MODULE = "_io"


def _check_mode_str(mode):
    # check type
    if not isinstance(mode, str):
        return False
    # check syntax
    modes = set(mode)
    _mode = "rwatb+Ux"
    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:
            return False
        reading = True
    if text and binary:
        return False
    total = reading + writing + appending + creating
    if total > 1:
        return False
    if not (reading or writing or appending or creating):
        return False
    return True


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 https://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 https://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.",
        ),
        "W1505": (
            "Using deprecated method %s()",
            "deprecated-method",
            "The method is marked as deprecated and will be removed in "
            "a future version of Python. Consider looking for an "
            "alternative in the documentation.",
        ),
        "W1506": (
            "threading.Thread needs the target function",
            "bad-thread-instantiation",
            "The warning is emitted when a threading.Thread class "
            "is instantiated without the target function being passed. "
            "By default, the first parameter is the group param, not the target param. ",
        ),
        "W1507": (
            "Using copy.copy(os.environ). Use os.environ.copy() instead. ",
            "shallow-copy-environ",
            "os.environ is not a dict object but proxy object, so "
            "shallow copy has still effects on original object. "
            "See https://bugs.python.org/issue15373 for reference. ",
        ),
        "E1507": (
            "%s does not support %s type argument",
            "invalid-envvar-value",
            "Env manipulation functions support only string type arguments. "
            "See https://docs.python.org/3/library/os.html#os.getenv. ",
        ),
        "W1508": (
            "%s default type is %s. Expected str or None.",
            "invalid-envvar-default",
            "Env manipulation functions return None or str values. "
            "Supplying anything different as a default may cause bugs. "
            "See https://docs.python.org/3/library/os.html#os.getenv. ",
        ),
        "W1509": (
            "Using preexec_fn keyword which may be unsafe in the presence "
            "of threads",
            "subprocess-popen-preexec-fn",
            "The preexec_fn parameter is not safe to use in the presence "
            "of threads in your application. The child process could "
            "deadlock before exec is called. If you must use it, keep it "
            "trivial! Minimize the number of libraries you call into."
            "https://docs.python.org/3/library/subprocess.html#popen-constructor",
        ),
        "W1510": (
            "Using subprocess.run without explicitly set `check` is not recommended.",
            "subprocess-run-check",
            "The check parameter should always be used with explicitly set "
            "`check` keyword to make clear what the error-handling behavior is."
            "https://docs.python.org/3/library/subprocess.html#subprocess.run",
        ),
    }

    deprecated = {
        0: {
            "cgi.parse_qs",
            "cgi.parse_qsl",
            "ctypes.c_buffer",
            "distutils.command.register.register.check_metadata",
            "distutils.command.sdist.sdist.check_metadata",
            "tkinter.Misc.tk_menuBar",
            "tkinter.Menu.tk_bindForTraversal",
        },
        2: {
            (2, 6, 0): {
                "commands.getstatus",
                "os.popen2",
                "os.popen3",
                "os.popen4",
                "macostools.touched",
            },
            (2, 7, 0): {
                "unittest.case.TestCase.assertEquals",
                "unittest.case.TestCase.assertNotEquals",
                "unittest.case.TestCase.assertAlmostEquals",
                "unittest.case.TestCase.assertNotAlmostEquals",
                "unittest.case.TestCase.assert_",
                "xml.etree.ElementTree.Element.getchildren",
                "xml.etree.ElementTree.Element.getiterator",
                "xml.etree.ElementTree.XMLParser.getiterator",
                "xml.etree.ElementTree.XMLParser.doctype",
            },
        },
        3: {
            (3, 0, 0): {
                "inspect.getargspec",
                "failUnlessEqual",
                "assertEquals",
                "failIfEqual",
                "assertNotEquals",
                "failUnlessAlmostEqual",
                "assertAlmostEquals",
                "failIfAlmostEqual",
                "assertNotAlmostEquals",
                "failUnless",
                "assert_",
                "failUnlessRaises",
                "failIf",
                "assertRaisesRegexp",
                "assertRegexpMatches",
                "assertNotRegexpMatches",
            },
            (3, 1, 0): {
                "base64.encodestring",
                "base64.decodestring",
                "ntpath.splitunc",
            },
            (3, 2, 0): {
                "cgi.escape",
                "configparser.RawConfigParser.readfp",
                "xml.etree.ElementTree.Element.getchildren",
                "xml.etree.ElementTree.Element.getiterator",
                "xml.etree.ElementTree.XMLParser.getiterator",
                "xml.etree.ElementTree.XMLParser.doctype",
            },
            (3, 3, 0): {
                "inspect.getmoduleinfo",
                "logging.warn",
                "logging.Logger.warn",
                "logging.LoggerAdapter.warn",
                "nntplib._NNTPBase.xpath",
                "platform.popen",
            },
            (3, 4, 0): {
                "importlib.find_loader",
                "plistlib.readPlist",
                "plistlib.writePlist",
                "plistlib.readPlistFromBytes",
                "plistlib.writePlistToBytes",
            },
            (3, 4, 4): {"asyncio.tasks.async"},
            (3, 5, 0): {
                "fractions.gcd",
                "inspect.formatargspec",
                "inspect.getcallargs",
                "platform.linux_distribution",
                "platform.dist",
            },
            (3, 6, 0): {"importlib._bootstrap_external.FileLoader.load_module"},
        },
    }

    def _check_bad_thread_instantiation(self, node):
        if not node.kwargs and not node.keywords and len(node.args) <= 1:
            self.add_message("bad-thread-instantiation", node=node)

    def _check_for_preexec_fn_in_popen(self, node):
        if node.keywords:
            for keyword in node.keywords:
                if keyword.arg == "preexec_fn":
                    self.add_message("subprocess-popen-preexec-fn", node=node)

    def _check_for_check_kw_in_run(self, node):
        kwargs = {keyword.arg for keyword in (node.keywords or ())}
        if "check" not in kwargs:
            self.add_message("subprocess-run-check", node=node)

    def _check_shallow_copy_environ(self, node):
        arg = utils.get_argument_from_call(node, position=0)
        for inferred in arg.inferred():
            if inferred.qname() == OS_ENVIRON:
                self.add_message("shallow-copy-environ", node=node)
                break

    @utils.check_messages(
        "bad-open-mode",
        "redundant-unittest-assert",
        "deprecated-method",
        "bad-thread-instantiation",
        "shallow-copy-environ",
        "invalid-envvar-value",
        "invalid-envvar-default",
        "subprocess-popen-preexec-fn",
        "subprocess-run-check",
    )
    def visit_call(self, node):
        """Visit a Call node."""
        try:
            for inferred in node.func.infer():
                if inferred is astroid.Uninferable:
                    continue
                if inferred.root().name == OPEN_MODULE:
                    if getattr(node.func, "name", None) in OPEN_FILES:
                        self._check_open_mode(node)
                elif inferred.root().name == UNITTEST_CASE:
                    self._check_redundant_assert(node, inferred)
                elif isinstance(inferred, astroid.ClassDef):
                    if inferred.qname() == THREADING_THREAD:
                        self._check_bad_thread_instantiation(node)
                    elif inferred.qname() == SUBPROCESS_POPEN:
                        self._check_for_preexec_fn_in_popen(node)
                elif isinstance(inferred, astroid.FunctionDef):
                    name = inferred.qname()
                    if name == COPY_COPY:
                        self._check_shallow_copy_environ(node)
                    elif name in ENV_GETTERS:
                        self._check_env_function(node, inferred)
                    elif name == SUBPROCESS_RUN:
                        self._check_for_check_kw_in_run(node)
                self._check_deprecated_method(node, inferred)
        except astroid.InferenceError:
            return

    @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)

    def _check_deprecated_method(self, node, inferred):
        py_vers = sys.version_info[0]

        if isinstance(node.func, astroid.Attribute):
            func_name = node.func.attrname
        elif isinstance(node.func, astroid.Name):
            func_name = node.func.name
        else:
            # Not interested in other nodes.
            return

        # Reject nodes which aren't of interest to us.
        acceptable_nodes = (
            astroid.BoundMethod,
            astroid.UnboundMethod,
            astroid.FunctionDef,
        )
        if not isinstance(inferred, acceptable_nodes):
            return

        qname = inferred.qname()
        if any(name in self.deprecated[0] for name in (qname, func_name)):
            self.add_message("deprecated-method", node=node, args=(func_name,))
        else:
            for since_vers, func_list in self.deprecated[py_vers].items():
                if since_vers <= sys.version_info and any(
                    name in func_list for name in (qname, func_name)
                ):
                    self.add_message("deprecated-method", node=node, args=(func_name,))
                    break

    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 inferred.
        If so, emit boolean-datetime warning.
        """
        try:
            inferred = next(node.infer())
        except astroid.InferenceError:
            return
        if isinstance(inferred, Instance) and inferred.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_env_function(self, node, infer):
        env_name_kwarg = "key"
        env_value_kwarg = "default"
        if node.keywords:
            kwargs = {keyword.arg: keyword.value for keyword in node.keywords}
        else:
            kwargs = None
        if node.args:
            env_name_arg = node.args[0]
        elif kwargs and env_name_kwarg in kwargs:
            env_name_arg = kwargs[env_name_kwarg]
        else:
            env_name_arg = None

        if env_name_arg:
            self._check_invalid_envvar_value(
                node=node,
                message="invalid-envvar-value",
                call_arg=utils.safe_infer(env_name_arg),
                infer=infer,
                allow_none=False,
            )

        if len(node.args) == 2:
            env_value_arg = node.args[1]
        elif kwargs and env_value_kwarg in kwargs:
            env_value_arg = kwargs[env_value_kwarg]
        else:
            env_value_arg = None

        if env_value_arg:
            self._check_invalid_envvar_value(
                node=node,
                infer=infer,
                message="invalid-envvar-default",
                call_arg=utils.safe_infer(env_value_arg),
                allow_none=True,
            )

    def _check_invalid_envvar_value(self, node, infer, message, call_arg, allow_none):
        if call_arg in (astroid.Uninferable, None):
            return

        name = infer.qname()
        if isinstance(call_arg, Const):
            emit = False
            if call_arg.value is None:
                emit = not allow_none
            elif not isinstance(call_arg.value, str):
                emit = True
            if emit:
                self.add_message(message, node=node, args=(name, call_arg.pytype()))
        else:
            self.add_message(message, node=node, args=(name, call_arg.pytype()))


def register(linter):
    """required method to auto register this checker """
    linter.register_checker(StdlibChecker(linter))