Revert "Revert "pylint: upgrade to 1.3.1""

third_party/pylint/checkers/exceptions.py

-# Copyright (c) 2003-2007 LOGILAB S.A. (Paris, FRANCE).
+# Copyright (c) 2003-2013 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.
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 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
+import astroid
+from astroid import YES, Instance, unpack_infer
 
 from pylint.checkers import BaseChecker
-from pylint.checkers.utils import is_empty, is_raising
-from pylint.interfaces import IASTNGChecker
+from pylint.checkers.utils import is_empty, is_raising, check_messages
+from pylint.interfaces import IAstroidChecker
 
+def infer_bases(klass):
+    """ Fully infer the bases of the klass node.
 
+    This doesn't use .ancestors(), because we need
+    the non-inferable nodes (YES nodes),
+    which can't be retrieved from .ancestors()
+    """
+    for base in klass.bases:
+        try:
+            inferit = base.infer().next()
+        except astroid.InferenceError:
+            continue
+        if inferit is YES:
+            yield inferit
+        else:
+            for base in infer_bases(inferit):
+                yield base
+
+PY3K = sys.version_info >= (3, 0)
 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.'),
+    'E0701': ('Bad except clauses order (%s)',
+              'bad-except-order',
+              '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',
+              'raising-bad-type',
               'Used when something which is neither a class, an instance or a \
               string is raised (i.e. a `TypeError` will be raised).'),
+    'E0703': ('Exception context set to something which is not an '
+              'exception, nor None',
+              'bad-exception-context',
+              'Used when using the syntax "raise ... from ...", '
+              'where the exception context is not an exception, '
+              'nor None.',
+              {'minversion': (3, 0)}),
     'E0710': ('Raising a new style class which doesn\'t inherit from BaseException',
+              'raising-non-exception',
               'Used when a new style class which doesn\'t inherit from \
                BaseException is raised.'),
     'E0711': ('NotImplemented raised - should raise NotImplementedError',
+              'notimplemented-raised',
               'Used when NotImplemented is raised instead of \
               NotImplementedError'),
-    
+    'E0712': ('Catching an exception which doesn\'t inherit from BaseException: %s',
+              'catching-non-exception',
+              'Used when a class which doesn\'t inherit from \
+               BaseException is used as an exception in an except clause.'),
+
     'W0701': ('Raising a string exception',
+              'raising-string',
               'Used when a string exception is raised.'),
     'W0702': ('No exception type(s) specified',
+              'bare-except',
               'Used when an except clause doesn\'t specify exceptions type to \
               catch.'),
     'W0703': ('Catching too general exception %s',
+              'broad-except',
               'Used when an except catches a too general exception, \
               possibly burying unrelated errors.'),
     'W0704': ('Except doesn\'t do anything',
+              'pointless-except',
               'Used when an except clause does nothing but "pass" and there is\
               no "else" clause.'),
     'W0710': ('Exception doesn\'t inherit from standard "Exception" class',
+              'nonstandard-exception',
               'Used when a custom exception class is raised but doesn\'t \
-              inherit from the builtin "Exception" class.'),
+              inherit from the builtin "Exception" class.',
+              {'maxversion': (3, 0)}),
+    'W0711': ('Exception to catch is the result of a binary "%s" operation',
+              'binary-op-exception',
+              'Used when the exception to catch is of the form \
+              "except A or B:".  If intending to catch multiple, \
+              rewrite as "except (A, B):"'),
+    'W0712': ('Implicit unpacking of exceptions is not supported in Python 3',
+              'unpacking-in-except',
+              'Python3 will not allow implicit unpacking of exceptions in except '
+              'clauses. '
+              'See http://www.python.org/dev/peps/pep-3110/',
+              {'maxversion': (3, 0)}),
+    'W0713': ('Indexing exceptions will not work on Python 3',
+              'indexing-exception',
+              'Indexing exceptions will not work on Python 3. Use '
+              '`exception.args[index]` instead.',
+              {'maxversion': (3, 0)}),
     }
 
 
 if sys.version_info < (3, 0):
     EXCEPTIONS_MODULE = "exceptions"
 else:
     EXCEPTIONS_MODULE = "builtins"
 
 class ExceptionsChecker(BaseChecker):
-    """checks for                                                              
-    * excepts without exception filter                                         
+    """checks for
+    * excepts without exception filter
     * type of raise argument : string, Exceptions, other values
     """
-    
-    __implements__ = IASTNGChecker
+
+    __implements__ = IAstroidChecker
 
     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),)}
-                ),
-               )
+               ),
+              )
 
+    @check_messages('raising-string', 'nonstandard-exception', 'raising-bad-type',
+                    'raising-non-exception', 'notimplemented-raised', 'bad-exception-context')
     def visit_raise(self, node):
         """visit raise possibly inferring value"""
         # ignore empty raise
         if node.exc is None:
             return
+        if PY3K and node.cause:
+            try:
+                cause = node.cause.infer().next()
+            except astroid.InferenceError:
+                pass
+            else:
+                if cause is YES:
+                    return
+                if isinstance(cause, astroid.Const):
+                    if cause.value is not None:
+                        self.add_message('bad-exception-context',
+                                         node=node)
+                elif (not isinstance(cause, astroid.Class) and
+                      not inherit_from_std_ex(cause)):
+                    self.add_message('bad-exception-context',
+                                     node=node)
         expr = node.exc
         if self._check_raise_value(node, expr):
             return
         else:
             try:
                 value = unpack_infer(expr).next()
-            except astng.InferenceError:
+            except astroid.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):
+        if isinstance(expr, astroid.Const):
             value = expr.value
             if isinstance(value, str):
-                self.add_message('W0701', node=node)
+                self.add_message('raising-string', node=node)
             else:
-                self.add_message('E0702', node=node,
+                self.add_message('raising-bad-type', node=node,
                                  args=value.__class__.__name__)
-        elif (isinstance(expr, astng.Name) and \
+        elif (isinstance(expr, astroid.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)):
+                 isinstance(expr, (astroid.List, astroid.Dict, astroid.Tuple,
+                                   astroid.Module, astroid.Function)):
+            self.add_message('raising-bad-type', node=node, args=expr.name)
+        elif ((isinstance(expr, astroid.Name) and expr.name == 'NotImplemented')
+              or (isinstance(expr, astroid.CallFunc) and
+                  isinstance(expr.func, astroid.Name) and
+                  expr.func.name == 'NotImplemented')):
+            self.add_message('notimplemented-raised', node=node)
+        elif isinstance(expr, astroid.BinOp) and expr.op == '%':
+            self.add_message('raising-string', node=node)
+        elif isinstance(expr, (Instance, astroid.Class)):
             if isinstance(expr, Instance):
                 expr = expr._proxied
-            if (isinstance(expr, astng.Class) and
+            if (isinstance(expr, astroid.Class) and
                     not inherit_from_std_ex(expr) and
                     expr.root().name != BUILTINS_NAME):
                 if expr.newstyle:
-                    self.add_message('E0710', node=node)
+                    self.add_message('raising-non-exception', node=node)
                 else:
-                    self.add_message('W0710', node=node)
+                    self.add_message('nonstandard-exception', node=node)
             else:
                 value_found = False
         else:
             value_found = False
         return value_found
 
+    @check_messages('unpacking-in-except')
+    def visit_excepthandler(self, node):
+        """Visit an except handler block and check for exception unpacking."""
+        if isinstance(node.name, (astroid.Tuple, astroid.List)):
+            self.add_message('unpacking-in-except', node=node)
 
+    @check_messages('indexing-exception')
+    def visit_subscript(self, node):
+        """ Look for indexing exceptions. """
+        try:
+            for infered in node.value.infer():
+                if not isinstance(infered, astroid.Instance):
+                    continue
+                if inherit_from_std_ex(infered):
+                    self.add_message('indexing-exception', node=node)
+        except astroid.InferenceError:
+            return
+
+    @check_messages('bare-except', 'broad-except', 'pointless-except',
+                    'binary-op-exception', 'bad-except-order',
+                    'catching-non-exception')
     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 is_empty(handler.body) and not node.orelse:
+                self.add_message('pointless-except', 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)
+                if not is_raising(handler.body):
+                    self.add_message('bare-except', node=handler)
                 # check if a "except:" is followed by some other
                 # except
-                elif index < (nb_handlers - 1):
+                if index < (nb_handlers - 1):
                     msg = 'empty except clause should always appear last'
-                    self.add_message('E0701', node=node, args=msg)
+                    self.add_message('bad-except-order', node=node, args=msg)
+
+            elif isinstance(handler.type, astroid.BoolOp):
+                self.add_message('binary-op-exception', node=handler, args=handler.type.op)
             else:
                 try:
                     excs = list(unpack_infer(handler.type))
-                except astng.InferenceError:
+                except astroid.InferenceError:
                     continue
                 for exc in excs:
-                    # XXX skip other non class nodes 
-                    if exc is YES or not isinstance(exc, astng.Class):
+                    # XXX skip other non class nodes
+                    if exc is YES or not isinstance(exc, astroid.Class):
                         continue
                     exc_ancestors = [anc for anc in exc.ancestors()
-                                     if isinstance(anc, astng.Class)]
+                                     if isinstance(anc, astroid.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)
+                            self.add_message('bad-except-order', 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)
+                            and exc.root().name == EXCEPTIONS_MODULE
+                            and not is_raising(handler.body)):
+                        self.add_message('broad-except', args=exc.name, node=handler.type)
+
+                    if (not inherit_from_std_ex(exc) and
+                            exc.root().name != BUILTINS_NAME):
+                        # try to see if the exception is based on a C based
+                        # exception, by infering all the base classes and
+                        # looking for inference errors
+                        bases = infer_bases(exc)
+                        fully_infered = all(inferit is not YES
+                                            for inferit in bases)
+                        if fully_infered:
+                            self.add_message('catching-non-exception',
+                                             node=handler.type,
+                                             args=(exc.name, ))
+
                 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))