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# -*- coding: utf-8 -*-
# Copyright (c) 2009-2011, 2013-2014 LOGILAB S.A. (Paris, FRANCE) <contact@logilab.fr>
# Copyright (c) 2009, 2012, 2014 Google, Inc.
# Copyright (c) 2012 Mike Bryant <leachim@leachim.info>
# Copyright (c) 2014 Brett Cannon <brett@python.org>
# Copyright (c) 2014 Arun Persaud <arun@nubati.net>
# Copyright (c) 2015-2018 Claudiu Popa <pcmanticore@gmail.com>
# Copyright (c) 2015 Ionel Cristian Maries <contact@ionelmc.ro>
# Copyright (c) 2016 Chris Murray <chris@chrismurray.scot>
# Copyright (c) 2016 Ashley Whetter <ashley@awhetter.co.uk>
# Copyright (c) 2017 guillaume2 <guillaume.peillex@gmail.col>
# Copyright (c) 2017 Łukasz Rogalski <rogalski.91@gmail.com>
# Copyright (c) 2018 Mike Frysinger <vapier@gmail.com>
# Copyright (c) 2018 Mariatta Wijaya <mariatta@python.org>
# 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
"""checker for use of Python logging
"""
import string
import astroid
from pylint import checkers
from pylint import interfaces
from pylint.checkers import utils
from pylint.checkers.utils import check_messages
MSGS = {
"W1201": (
"Specify string format arguments as logging function parameters",
"logging-not-lazy",
"Used when a logging statement has a call form of "
'"logging.<logging method>(format_string % (format_args...))". '
"Such calls should leave string interpolation to the logging "
"method itself and be written "
'"logging.<logging method>(format_string, format_args...)" '
"so that the program may avoid incurring the cost of the "
"interpolation in those cases in which no message will be "
"logged. For more, see "
"http://www.python.org/dev/peps/pep-0282/.",
),
"W1202": (
"Use % formatting in logging functions and pass the % "
"parameters as arguments",
"logging-format-interpolation",
"Used when a logging statement has a call form of "
'"logging.<logging method>(format_string.format(format_args...))"'
". Such calls should use % formatting instead, but leave "
"interpolation to the logging function by passing the parameters "
"as arguments.",
),
"W1203": (
"Use % formatting in logging functions and pass the % "
"parameters as arguments",
"logging-fstring-interpolation",
"Used when a logging statement has a call form of "
'"logging.method(f"..."))"'
". Such calls should use % formatting instead, but leave "
"interpolation to the logging function by passing the parameters "
"as arguments.",
),
"E1200": (
"Unsupported logging format character %r (%#02x) at index %d",
"logging-unsupported-format",
"Used when an unsupported format character is used in a logging "
"statement format string.",
),
"E1201": (
"Logging format string ends in middle of conversion specifier",
"logging-format-truncated",
"Used when a logging statement format string terminates before "
"the end of a conversion specifier.",
),
"E1205": (
"Too many arguments for logging format string",
"logging-too-many-args",
"Used when a logging format string is given too many arguments.",
),
"E1206": (
"Not enough arguments for logging format string",
"logging-too-few-args",
"Used when a logging format string is given too few arguments.",
),
}
CHECKED_CONVENIENCE_FUNCTIONS = {
"critical",
"debug",
"error",
"exception",
"fatal",
"info",
"warn",
"warning",
}
def is_method_call(func, types=(), methods=()):
"""Determines if a BoundMethod node represents a method call.
Args:
func (astroid.BoundMethod): The BoundMethod AST node to check.
types (Optional[String]): Optional sequence of caller type names to restrict check.
methods (Optional[String]): Optional sequence of method names to restrict check.
Returns:
bool: true if the node represents a method call for the given type and
method names, False otherwise.
"""
return (
isinstance(func, astroid.BoundMethod)
and isinstance(func.bound, astroid.Instance)
and (func.bound.name in types if types else True)
and (func.name in methods if methods else True)
)
class LoggingChecker(checkers.BaseChecker):
"""Checks use of the logging module."""
__implements__ = interfaces.IAstroidChecker
name = "logging"
msgs = MSGS
options = (
(
"logging-modules",
{
"default": ("logging",),
"type": "csv",
"metavar": "<comma separated list>",
"help": "Logging modules to check that the string format "
"arguments are in logging function parameter format.",
},
),
(
"logging-format-style",
{
"default": "old",
"type": "choice",
"metavar": "<old (%) or new ({)>",
"choices": ["old", "new"],
"help": "Format style used to check logging format string. "
"`old` means using % formatting, while `new` is for `{}` formatting.",
},
),
)
def visit_module(self, node): # pylint: disable=unused-argument
"""Clears any state left in this checker from last module checked."""
# The code being checked can just as easily "import logging as foo",
# so it is necessary to process the imports and store in this field
# what name the logging module is actually given.
self._logging_names = set()
logging_mods = self.config.logging_modules
self._format_style = self.config.logging_format_style
self._logging_modules = set(logging_mods)
self._from_imports = {}
for logging_mod in logging_mods:
parts = logging_mod.rsplit(".", 1)
if len(parts) > 1:
self._from_imports[parts[0]] = parts[1]
def visit_importfrom(self, node):
"""Checks to see if a module uses a non-Python logging module."""
try:
logging_name = self._from_imports[node.modname]
for module, as_name in node.names:
if module == logging_name:
self._logging_names.add(as_name or module)
except KeyError:
pass
def visit_import(self, node):
"""Checks to see if this module uses Python's built-in logging."""
for module, as_name in node.names:
if module in self._logging_modules:
self._logging_names.add(as_name or module)
@check_messages(*MSGS)
def visit_call(self, node):
"""Checks calls to logging methods."""
def is_logging_name():
return (
isinstance(node.func, astroid.Attribute)
and isinstance(node.func.expr, astroid.Name)
and node.func.expr.name in self._logging_names
)
def is_logger_class():
try:
for inferred in node.func.infer():
if isinstance(inferred, astroid.BoundMethod):
parent = inferred._proxied.parent
if isinstance(parent, astroid.ClassDef) and (
parent.qname() == "logging.Logger"
or any(
ancestor.qname() == "logging.Logger"
for ancestor in parent.ancestors()
)
):
return True, inferred._proxied.name
except astroid.exceptions.InferenceError:
pass
return False, None
if is_logging_name():
name = node.func.attrname
else:
result, name = is_logger_class()
if not result:
return
self._check_log_method(node, name)
def _check_log_method(self, node, name):
"""Checks calls to logging.log(level, format, *format_args)."""
if name == "log":
if node.starargs or node.kwargs or len(node.args) < 2:
# Either a malformed call, star args, or double-star args. Beyond
# the scope of this checker.
return
format_pos = 1
elif name in CHECKED_CONVENIENCE_FUNCTIONS:
if node.starargs or node.kwargs or not node.args:
# Either no args, star args, or double-star args. Beyond the
# scope of this checker.
return
format_pos = 0
else:
return
if isinstance(node.args[format_pos], astroid.BinOp):
binop = node.args[format_pos]
emit = binop.op == "%"
if binop.op == "+":
total_number_of_strings = sum(
1
for operand in (binop.left, binop.right)
if self._is_operand_literal_str(utils.safe_infer(operand))
)
emit = total_number_of_strings > 0
if emit:
self.add_message("logging-not-lazy", node=node)
elif isinstance(node.args[format_pos], astroid.Call):
self._check_call_func(node.args[format_pos])
elif isinstance(node.args[format_pos], astroid.Const):
self._check_format_string(node, format_pos)
elif isinstance(
node.args[format_pos], (astroid.FormattedValue, astroid.JoinedStr)
):
self.add_message("logging-fstring-interpolation", node=node)
@staticmethod
def _is_operand_literal_str(operand):
"""
Return True if the operand in argument is a literal string
"""
return isinstance(operand, astroid.Const) and operand.name == "str"
def _check_call_func(self, node):
"""Checks that function call is not format_string.format().
Args:
node (astroid.node_classes.Call):
Call AST node to be checked.
"""
func = utils.safe_infer(node.func)
types = ("str", "unicode")
methods = ("format",)
if is_method_call(func, types, methods) and not is_complex_format_str(
func.bound
):
self.add_message("logging-format-interpolation", node=node)
def _check_format_string(self, node, format_arg):
"""Checks that format string tokens match the supplied arguments.
Args:
node (astroid.node_classes.NodeNG): AST node to be checked.
format_arg (int): Index of the format string in the node arguments.
"""
num_args = _count_supplied_tokens(node.args[format_arg + 1 :])
if not num_args:
# If no args were supplied, then all format strings are valid -
# don't check any further.
return
format_string = node.args[format_arg].value
if not isinstance(format_string, str):
# If the log format is constant non-string (e.g. logging.debug(5)),
# ensure there are no arguments.
required_num_args = 0
else:
try:
if self._format_style == "old":
keyword_args, required_num_args, _, _ = utils.parse_format_string(
format_string
)
if keyword_args:
# Keyword checking on logging strings is complicated by
# special keywords - out of scope.
return
elif self._format_style == "new":
keys, num_args, manual_pos_arg = utils.parse_format_method_string(
format_string
)
kargs = len(set(k for k, l in keys if not isinstance(k, int)))
required_num_args = kargs + num_args + manual_pos_arg
except utils.UnsupportedFormatCharacter as ex:
char = format_string[ex.index]
self.add_message(
"logging-unsupported-format",
node=node,
args=(char, ord(char), ex.index),
)
return
except utils.IncompleteFormatString:
self.add_message("logging-format-truncated", node=node)
return
if num_args > required_num_args:
self.add_message("logging-too-many-args", node=node)
elif num_args < required_num_args:
self.add_message("logging-too-few-args", node=node)
def is_complex_format_str(node):
"""Checks if node represents a string with complex formatting specs.
Args:
node (astroid.node_classes.NodeNG): AST node to check
Returns:
bool: True if inferred string uses complex formatting, False otherwise
"""
inferred = utils.safe_infer(node)
if inferred is None or not isinstance(inferred.value, str):
return True
try:
parsed = list(string.Formatter().parse(inferred.value))
except ValueError:
# This format string is invalid
return False
for _, _, format_spec, _ in parsed:
if format_spec:
return True
return False
def _count_supplied_tokens(args):
"""Counts the number of tokens in an args list.
The Python log functions allow for special keyword arguments: func,
exc_info and extra. To handle these cases correctly, we only count
arguments that aren't keywords.
Args:
args (list): AST nodes that are arguments for a log format string.
Returns:
int: Number of AST nodes that aren't keywords.
"""
return sum(1 for arg in args if not isinstance(arg, astroid.Keyword))
def register(linter):
"""Required method to auto-register this checker."""
linter.register_checker(LoggingChecker(linter))