A checker for use (and misuse) of the standard logging module.

1 files changed, 101 insertions, 0 deletions

diff --git a/checkers/logging.py b/checkers/logging.py
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+# Copyright (c) 2009 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 compiler.ast
+
+from logilab import astng
+from pylint import checkers
+from pylint import interfaces
+
+
+EAGER_STRING_INTERPOLATION = 'W6501'
+
+CHECKED_CONVENIENCE_FUNCTIONS = set([
+    'critical', 'debug', 'error', 'exception', 'fatal', 'info', 'warn',
+    'warning'])
+
+
+class LoggingChecker(checkers.BaseChecker):
+  """Checks use of the logging module."""
+
+  __implements__ = interfaces.IASTNGChecker
+
+  name = 'logging'
+
+  msgs = {EAGER_STRING_INTERPOLATION:
+          ('Specify string format arguments as logging function parameters',
+           '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...)".')
+          }
+
+  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'
+
+  def visit_callfunc(self, node):
+    """Checks calls to (simple forms of) logging methods."""
+    if (not isinstance(node.func, astng.Getattr)
+        or not isinstance(node.func.expr, astng.Name)
+        or node.func.expr.name != self._logging_name):
+      return
+    self._CheckConvenienceMethods(node)
+    self._CheckLogMethod(node)
+
+  def _CheckConvenienceMethods(self, node):
+    """Checks calls to logging convenience methods (like logging.warn)."""
+    if node.func.attrname not in CHECKED_CONVENIENCE_FUNCTIONS:
+      return
+
+    if not node.args:
+      # Either no args, or star args, or double-star args. Beyond the
+      # scope of this checker in any case.
+      return
+
+    if isinstance(node.args[0], astng.BinOp) and node.args[0].op == '%':
+      self.add_message(EAGER_STRING_INTERPOLATION, node=node)
+
+  def _CheckLogMethod(self, node):
+    """Checks calls to logging.log(level, format, *format_args)."""
+    if node.func.attrname != 'log':
+      return
+
+    if len(node.args) < 2:
+      # Either a malformed call or something with crazy star args or
+      # double-star args magic. Beyond the scope of this checker.
+      return
+
+    if isinstance(node.args[1], astng.BinOp) and node.args[1].op == '%':
+      self.add_message(EAGER_STRING_INTERPOLATION, node=node)
+
+
+def register(linter):
+  """Required method to auto-register this checker."""
+  linter.register_checker(LoggingChecker(linter))