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# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt
"""Checker for use of Python logging."""
from __future__ import annotations
import string
import sys
from typing import TYPE_CHECKING
import astroid
from astroid import bases, nodes
from astroid.typing import InferenceResult
from pylint import checkers
from pylint.checkers import utils
from pylint.checkers.utils import infer_all
from pylint.typing import MessageDefinitionTuple
if sys.version_info >= (3, 8):
from typing import Literal
else:
from typing_extensions import Literal
if TYPE_CHECKING:
from pylint.lint import PyLinter
MSGS: dict[
str, MessageDefinitionTuple
] = { # pylint: disable=consider-using-namedtuple-or-dataclass
"W1201": (
"Use %s formatting in logging functions",
"logging-not-lazy",
"Used when a logging statement has a call form of "
'"logging.<logging method>(format_string % (format_args...))". '
"Use another type of string formatting instead. "
"You can use % formatting but leave interpolation to "
"the logging function by passing the parameters as arguments. "
"If logging-fstring-interpolation is disabled then "
"you can use fstring formatting. "
"If logging-format-interpolation is disabled then "
"you can use str.format.",
),
"W1202": (
"Use %s formatting in logging functions",
"logging-format-interpolation",
"Used when a logging statement has a call form of "
'"logging.<logging method>(format_string.format(format_args...))". '
"Use another type of string formatting instead. "
"You can use % formatting but leave interpolation to "
"the logging function by passing the parameters as arguments. "
"If logging-fstring-interpolation is disabled then "
"you can use fstring formatting. "
"If logging-not-lazy is disabled then "
"you can use % formatting as normal.",
),
"W1203": (
"Use %s formatting in logging functions",
"logging-fstring-interpolation",
"Used when a logging statement has a call form of "
'"logging.<logging method>(f"...")".'
"Use another type of string formatting instead. "
"You can use % formatting but leave interpolation to "
"the logging function by passing the parameters as arguments. "
"If logging-format-interpolation is disabled then "
"you can use str.format. "
"If logging-not-lazy is disabled then "
"you can use % formatting as normal.",
),
"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",
}
MOST_COMMON_FORMATTING = frozenset(["%s", "%d", "%f", "%r"])
def is_method_call(
func: bases.BoundMethod, types: tuple[str, ...] = (), methods: tuple[str, ...] = ()
) -> bool:
"""Determines if a BoundMethod node represents a method call.
Args:
func: The BoundMethod AST node to check.
types: Optional sequence of caller type names to restrict check.
methods: Optional sequence of method names to restrict check.
Returns:
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."""
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": "The type of string formatting that logging methods do. "
"`old` means using % formatting, `new` is for `{}` formatting.",
},
),
)
def visit_module(self, _: nodes.Module) -> None:
"""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[str] = set()
logging_mods = self.linter.config.logging_modules
self._format_style = self.linter.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: nodes.ImportFrom) -> None:
"""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: nodes.Import) -> None:
"""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)
def visit_call(self, node: nodes.Call) -> None:
"""Checks calls to logging methods."""
def is_logging_name() -> bool:
return (
isinstance(node.func, nodes.Attribute)
and isinstance(node.func.expr, nodes.Name)
and node.func.expr.name in self._logging_names
)
def is_logger_class() -> tuple[bool, str | None]:
for inferred in infer_all(node.func):
if isinstance(inferred, astroid.BoundMethod):
parent = inferred._proxied.parent
if isinstance(parent, nodes.ClassDef) and (
parent.qname() == "logging.Logger"
or any(
ancestor.qname() == "logging.Logger"
for ancestor in parent.ancestors()
)
):
return True, inferred._proxied.name
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: nodes.Call, name: str) -> None:
"""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: Literal[0, 1] = 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
format_arg = node.args[format_pos]
if isinstance(format_arg, nodes.BinOp):
binop = format_arg
emit = binop.op == "%"
if binop.op == "+" and not self._is_node_explicit_str_concatenation(binop):
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,
args=(self._helper_string(node),),
)
elif isinstance(format_arg, nodes.Call):
self._check_call_func(format_arg)
elif isinstance(format_arg, nodes.Const):
self._check_format_string(node, format_pos)
elif isinstance(format_arg, nodes.JoinedStr):
if str_formatting_in_f_string(format_arg):
return
self.add_message(
"logging-fstring-interpolation",
node=node,
args=(self._helper_string(node),),
)
def _helper_string(self, node: nodes.Call) -> str:
"""Create a string that lists the valid types of formatting for this node."""
valid_types = ["lazy %"]
if not self.linter.is_message_enabled(
"logging-fstring-formatting", node.fromlineno
):
valid_types.append("fstring")
if not self.linter.is_message_enabled(
"logging-format-interpolation", node.fromlineno
):
valid_types.append(".format()")
if not self.linter.is_message_enabled("logging-not-lazy", node.fromlineno):
valid_types.append("%")
return " or ".join(valid_types)
@staticmethod
def _is_operand_literal_str(operand: InferenceResult | None) -> bool:
"""Return True if the operand in argument is a literal string."""
return isinstance(operand, nodes.Const) and operand.name == "str"
@staticmethod
def _is_node_explicit_str_concatenation(node: nodes.NodeNG) -> bool:
"""Return True if the node represents an explicitly concatenated string."""
if not isinstance(node, nodes.BinOp):
return False
return (
LoggingChecker._is_operand_literal_str(node.left)
or LoggingChecker._is_node_explicit_str_concatenation(node.left)
) and (
LoggingChecker._is_operand_literal_str(node.right)
or LoggingChecker._is_node_explicit_str_concatenation(node.right)
)
def _check_call_func(self, node: nodes.Call) -> None:
"""Checks that function call is not format_string.format()."""
func = utils.safe_infer(node.func)
types = ("str", "unicode")
methods = ("format",)
if (
isinstance(func, astroid.BoundMethod)
and is_method_call(func, types, methods)
and not is_complex_format_str(func.bound)
):
self.add_message(
"logging-format-interpolation",
node=node,
args=(self._helper_string(node),),
)
def _check_format_string(self, node: nodes.Call, format_arg: Literal[0, 1]) -> None:
"""Checks that format string tokens match the supplied arguments.
Args:
node: AST node to be checked.
format_arg: 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 the string is not interpolated and can contain
# formatting characters - it's used verbatim. Don't check any further.
return
format_string = node.args[format_arg].value
required_num_args = 0
if isinstance(format_string, bytes):
format_string = format_string.decode()
if isinstance(format_string, str):
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":
(
keyword_arguments,
implicit_pos_args,
explicit_pos_args,
) = utils.parse_format_method_string(format_string)
keyword_args_cnt = len(
{k for k, _ in keyword_arguments if not isinstance(k, int)}
)
required_num_args = (
keyword_args_cnt + implicit_pos_args + explicit_pos_args
)
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: nodes.NodeNG) -> bool:
"""Return whether the node represents a string with complex formatting specs."""
inferred = utils.safe_infer(node)
if inferred is None or not (
isinstance(inferred, nodes.Const) and isinstance(inferred.value, str)
):
return True
try:
parsed = list(string.Formatter().parse(inferred.value))
except ValueError:
# This format string is invalid
return False
return any(format_spec for (_, _, format_spec, _) in parsed)
def _count_supplied_tokens(args: list[nodes.NodeNG]) -> int:
"""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: AST nodes that are arguments for a log format string.
Returns:
Number of AST nodes that aren't keywords.
"""
return sum(1 for arg in args if not isinstance(arg, nodes.Keyword))
def str_formatting_in_f_string(node: nodes.JoinedStr) -> bool:
"""Determine whether the node represents an f-string with string formatting.
For example: `f'Hello %s'`
"""
# Check "%" presence first for performance.
return any(
"%" in val.value and any(x in val.value for x in MOST_COMMON_FORMATTING)
for val in node.values
if isinstance(val, nodes.Const)
)
def register(linter: PyLinter) -> None:
linter.register_checker(LoggingChecker(linter))
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