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# Copyright (c) 2009-2010 Google, Inc.
# 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.,
# 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
"""checker for use of Python logging
"""
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/.'),
'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 few arguments.'),
'E1206': ('Not enough arguments for logging format string',
'logging-too-few-args',
'Used when a logging format string is given too many arguments'),
}
CHECKED_CONVENIENCE_FUNCTIONS = set([
'critical', 'debug', 'error', 'exception', 'fatal', 'info', 'warn',
'warning'])
class LoggingChecker(checkers.BaseChecker):
"""Checks use of the logging module."""
__implements__ = interfaces.IAstroidChecker
name = 'logging'
msgs = MSGS
def visit_module(self, unused_node):
"""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_name = None
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 == 'logging':
if as_name:
self._logging_name = as_name
else:
self._logging_name = 'logging'
@check_messages(*(MSGS.keys()))
def visit_callfunc(self, node):
"""Checks calls to (simple forms of) logging methods."""
if (not isinstance(node.func, astroid.Getattr)
or not isinstance(node.func.expr, astroid.Name)):
return
try:
logger_class = [inferred for inferred in node.func.expr.infer() if (
isinstance(inferred, astroid.Instance)
and any(ancestor for ancestor in inferred._proxied.ancestors() if (
ancestor.name == 'Logger'
and ancestor.parent.name == 'logging')))]
except astroid.exceptions.InferenceError:
return
if (node.func.expr.name != self._logging_name and not logger_class):
return
self._check_convenience_methods(node)
self._check_log_methods(node)
def _check_convenience_methods(self, node):
"""Checks calls to logging convenience methods (like logging.warn)."""
if node.func.attrname not in CHECKED_CONVENIENCE_FUNCTIONS:
return
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
if isinstance(node.args[0], astroid.BinOp) and node.args[0].op == '%':
self.add_message('W1201', node=node)
elif isinstance(node.args[0], astroid.Const):
self._check_format_string(node, 0)
def _check_log_methods(self, node):
"""Checks calls to logging.log(level, format, *format_args)."""
if node.func.attrname != 'log':
return
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
if isinstance(node.args[1], astroid.BinOp) and node.args[1].op == '%':
self.add_message('W1201', node=node)
elif isinstance(node.args[1], astroid.Const):
self._check_format_string(node, 1)
def _check_format_string(self, node, format_arg):
"""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 = self._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, basestring):
# If the log format is constant non-string (e.g. logging.debug(5)),
# ensure there are no arguments.
required_num_args = 0
else:
try:
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
except utils.UnsupportedFormatCharacter, e:
c = format_string[e.index]
self.add_message('E1200', node=node, args=(c, ord(c), e.index))
return
except utils.IncompleteFormatString:
self.add_message('E1201', node=node)
return
if num_args > required_num_args:
self.add_message('E1205', node=node)
elif num_args < required_num_args:
self.add_message('E1206', node=node)
def _count_supplied_tokens(self, 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 of 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, astroid.Keyword))
def register(linter):
"""Required method to auto-register this checker."""
linter.register_checker(LoggingChecker(linter))
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