Add pylint to depot_tools.

third_party/pylint/checkers/exceptions.py

+# Copyright (c) 2003-2007 LOGILAB S.A. (Paris, FRANCE).
+# http://www.logilab.fr/ -- mailto:contact@logilab.fr
+# 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.
+"""exceptions handling (raising, catching, exceptions classes) checker
+"""
+import sys
+
+from logilab.common.compat import builtins
+BUILTINS_NAME = builtins.__name__
+from logilab import astng
+from logilab.astng import YES, Instance, unpack_infer
+
+from pylint.checkers import BaseChecker
+from pylint.checkers.utils import is_empty, is_raising
+from pylint.interfaces import IASTNGChecker
+
+
+OVERGENERAL_EXCEPTIONS = ('Exception',)
+
+MSGS = {
+    'E0701': (
+    'Bad except clauses order (%s)',
+    'Used when except clauses are not in the correct order (from the \
+    more specific to the more generic). If you don\'t fix the order, \
+    some exceptions may not be catched by the most specific handler.'),
+    'E0702': ('Raising %s while only classes, instances or string are allowed',
+              'Used when something which is neither a class, an instance or a \
+              string is raised (i.e. a `TypeError` will be raised).'),
+    'E0710': ('Raising a new style class which doesn\'t inherit from BaseException',
+              'Used when a new style class which doesn\'t inherit from \
+               BaseException is raised.'),
+    'E0711': ('NotImplemented raised - should raise NotImplementedError',
+              'Used when NotImplemented is raised instead of \
+              NotImplementedError'),
+    
+    'W0701': ('Raising a string exception',
+              'Used when a string exception is raised.'),
+    'W0702': ('No exception type(s) specified',
+              'Used when an except clause doesn\'t specify exceptions type to \
+              catch.'),
+    'W0703': ('Catching too general exception %s',
+              'Used when an except catches a too general exception, \
+              possibly burying unrelated errors.'),
+    'W0704': ('Except doesn\'t do anything',
+              'Used when an except clause does nothing but "pass" and there is\
+              no "else" clause.'),
+    'W0710': ('Exception doesn\'t inherit from standard "Exception" class',
+              'Used when a custom exception class is raised but doesn\'t \
+              inherit from the builtin "Exception" class.'),
+    }
+
+
+if sys.version_info < (3, 0):
+    EXCEPTIONS_MODULE = "exceptions"
+else:
+    EXCEPTIONS_MODULE = "builtins"
+
+class ExceptionsChecker(BaseChecker):
+    """checks for                                                              
+    * excepts without exception filter                                         
+    * type of raise argument : string, Exceptions, other values
+    """
+    
+    __implements__ = IASTNGChecker
+
+    name = 'exceptions'
+    msgs = MSGS
+    priority = -4
+    options = (('overgeneral-exceptions',
+                {'default' : OVERGENERAL_EXCEPTIONS,
+                 'type' :'csv', 'metavar' : '<comma-separated class names>',
+                 'help' : 'Exceptions that will emit a warning '
+                          'when being caught. Defaults to "%s"' % (
+                              ', '.join(OVERGENERAL_EXCEPTIONS),)}
+                ),
+               )
+
+    def visit_raise(self, node):
+        """visit raise possibly inferring value"""
+        # ignore empty raise
+        if node.exc is None:
+            return
+        expr = node.exc
+        if self._check_raise_value(node, expr):
+            return
+        else:
+            try:
+                value = unpack_infer(expr).next()
+            except astng.InferenceError:
+                return
+            self._check_raise_value(node, value)
+
+    def _check_raise_value(self, node, expr):
+        """check for bad values, string exception and class inheritance
+        """
+        value_found = True
+        if isinstance(expr, astng.Const):
+            value = expr.value
+            if isinstance(value, str):
+                self.add_message('W0701', node=node)
+            else:
+                self.add_message('E0702', node=node,
+                                 args=value.__class__.__name__)
+        elif (isinstance(expr, astng.Name) and \
+                 expr.name in ('None', 'True', 'False')) or \
+                 isinstance(expr, (astng.List, astng.Dict, astng.Tuple, 
+                                   astng.Module, astng.Function)):
+            self.add_message('E0702', node=node, args=expr.name)
+        elif ( (isinstance(expr, astng.Name) and expr.name == 'NotImplemented')
+               or (isinstance(expr, astng.CallFunc) and
+                   isinstance(expr.func, astng.Name) and
+                   expr.func.name == 'NotImplemented') ):
+            self.add_message('E0711', node=node)
+        elif isinstance(expr, astng.BinOp) and expr.op == '%':
+            self.add_message('W0701', node=node)
+        elif isinstance(expr, (Instance, astng.Class)):
+            if isinstance(expr, Instance):
+                expr = expr._proxied
+            if (isinstance(expr, astng.Class) and
+                    not inherit_from_std_ex(expr) and
+                    expr.root().name != BUILTINS_NAME):
+                if expr.newstyle:
+                    self.add_message('E0710', node=node)
+                else:
+                    self.add_message('W0710', node=node)
+            else:
+                value_found = False
+        else:
+            value_found = False
+        return value_found
+
+
+    def visit_tryexcept(self, node):
+        """check for empty except"""
+        exceptions_classes = []
+        nb_handlers = len(node.handlers)
+        for index, handler  in enumerate(node.handlers):
+            # single except doing nothing but "pass" without else clause
+            if nb_handlers == 1 and is_empty(handler.body) and not node.orelse:
+                self.add_message('W0704', node=handler.type or handler.body[0])
+            if handler.type is None:
+                if nb_handlers == 1 and not is_raising(handler.body):
+                    self.add_message('W0702', node=handler)
+                # check if a "except:" is followed by some other
+                # except
+                elif index < (nb_handlers - 1):
+                    msg = 'empty except clause should always appear last'
+                    self.add_message('E0701', node=node, args=msg)
+            else:
+                try:
+                    excs = list(unpack_infer(handler.type))
+                except astng.InferenceError:
+                    continue
+                for exc in excs:
+                    # XXX skip other non class nodes 
+                    if exc is YES or not isinstance(exc, astng.Class):
+                        continue
+                    exc_ancestors = [anc for anc in exc.ancestors()
+                                     if isinstance(anc, astng.Class)]
+                    for previous_exc in exceptions_classes:
+                        if previous_exc in exc_ancestors:
+                            msg = '%s is an ancestor class of %s' % (
+                                previous_exc.name, exc.name)
+                            self.add_message('E0701', node=handler.type, args=msg)
+                    if (exc.name in self.config.overgeneral_exceptions
+                        and exc.root().name == EXCEPTIONS_MODULE
+                        and nb_handlers == 1 and not is_raising(handler.body)):
+                        self.add_message('W0703', args=exc.name, node=handler.type)
+                exceptions_classes += excs
+
+
+def inherit_from_std_ex(node):
+    """return true if the given class node is subclass of
+    exceptions.Exception
+    """
+    if node.name in ('Exception', 'BaseException') \
+            and node.root().name == EXCEPTIONS_MODULE:
+        return True
+    for parent in node.ancestors(recurs=False):
+        if inherit_from_std_ex(parent):
+            return True
+    return False
+
+def register(linter):
+    """required method to auto register this checker"""
+    linter.register_checker(ExceptionsChecker(linter))