pylint: upgrade to 1.4.0

third_party/pylint/checkers/exceptions.py

 # 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.,
 # 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__
 import astroid
-from astroid import YES, Instance, unpack_infer
+from astroid import YES, Instance, unpack_infer, List, Tuple
 
 from pylint.checkers import BaseChecker
-from pylint.checkers.utils import is_empty, is_raising, check_messages
-from pylint.interfaces import IAstroidChecker
+from pylint.checkers.utils import (
+    is_empty, is_raising,
+    check_messages, inherit_from_std_ex,
+    EXCEPTIONS_MODULE, has_known_bases)
+from pylint.interfaces import IAstroidChecker, INFERENCE, INFERENCE_FAILURE
 
-def infer_bases(klass):
-    """ Fully infer the bases of the klass node.
+def _annotated_unpack_infer(stmt, context=None):
+    """
+    Recursively generate nodes inferred by the given statement.
+    If the inferred value is a list or a tuple, recurse on the elements.
+    Returns an iterator which yields tuples in the format
+    ('original node', 'infered node').
+    """
+    # TODO: the same code as unpack_infer, except for the annotated
+    # return. We need this type of annotation only here and
+    # there is no point in complicating the API for unpack_infer.
+    # If the need arises, this behaviour can be promoted to unpack_infer
+    # as well.
+    if isinstance(stmt, (List, Tuple)):
+        for elt in stmt.elts:
+            for infered_elt in unpack_infer(elt, context):
+                yield elt, infered_elt
+        return
+    # if infered is a final node, return it and stop
+    infered = next(stmt.infer(context))
+    if infered is stmt:
+        yield stmt, infered
+        return
+    # else, infer recursivly, except YES object that should be returned as is
+    for infered in stmt.infer(context):
+        if infered is YES:
+            yield stmt, infered
+        else:
+            for inf_inf in unpack_infer(infered, context):
+                yield stmt, inf_inf
 
-    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)',
               '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',
+    'E0702': ('Raising %s while only classes or instances 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.',
               {'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
     * type of raise argument : string, Exceptions, other values
     """
 
     __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')
+    @check_messages('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()
+                cause = next(node.cause.infer())
             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()
+                value = next(unpack_infer(expr))
             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, astroid.Const):
             value = expr.value
             if isinstance(value, str):
-                self.add_message('raising-string', node=node)
+                # raising-string will be emitted from python3 porting checker.
+                pass
             else:
                 self.add_message('raising-bad-type', node=node,
                                  args=value.__class__.__name__)
         elif (isinstance(expr, astroid.Name) and \
                  expr.name in ('None', 'True', 'False')) or \
                  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, astroid.Class) and
                     not inherit_from_std_ex(expr) and
                     expr.root().name != BUILTINS_NAME):
                 if expr.newstyle:
                     self.add_message('raising-non-exception', node=node)
                 else:
-                    self.add_message('nonstandard-exception', node=node)
+                    self.add_message(
+                        'nonstandard-exception', node=node,
+                        confidence=INFERENCE if has_known_bases(expr) else INFERENCE_FAILURE)
             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):
+        for index, handler in enumerate(node.handlers):
             # single except doing nothing but "pass" without else clause
             if is_empty(handler.body) and not node.orelse:
-                self.add_message('pointless-except', node=handler.type or handler.body[0])
+                self.add_message('pointless-except',
+                                 node=handler.type or handler.body[0])
             if handler.type is None:
                 if not is_raising(handler.body):
                     self.add_message('bare-except', node=handler)
                 # check if a "except:" is followed by some other
                 # except
                 if index < (nb_handlers - 1):
                     msg = 'empty except clause should always appear last'
                     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)
+                self.add_message('binary-op-exception',
+                                 node=handler, args=handler.type.op)
             else:
                 try:
-                    excs = list(unpack_infer(handler.type))
+                    excs = list(_annotated_unpack_infer(handler.type))
                 except astroid.InferenceError:
                     continue
-                for exc in excs:
-                    # XXX skip other non class nodes
-                    if exc is YES or not isinstance(exc, astroid.Class):
+                for part, exc in excs:
+                    if exc is YES:
                         continue
+                    if isinstance(exc, astroid.Instance) and inherit_from_std_ex(exc):
+                        exc = exc._proxied
+                    if not isinstance(exc, astroid.Class):
+                        # Don't emit the warning if the infered stmt
+                        # is None, but the exception handler is something else,
+                        # maybe it was redefined.
+                        if (isinstance(exc, astroid.Const) and
+                                exc.value is None):
+                            if ((isinstance(handler.type, astroid.Const) and
+                                 handler.type.value is None) or
+                                    handler.type.parent_of(exc)):
+                                # If the exception handler catches None or
+                                # the exception component, which is None, is
+                                # defined by the entire exception handler, then
+                                # emit a warning.
+                                self.add_message('catching-non-exception',
+                                                 node=handler.type,
+                                                 args=(part.as_string(), ))
+                        else:
+                            self.add_message('catching-non-exception',
+                                             node=handler.type,
+                                             args=(part.as_string(), ))
+                        continue
+
                     exc_ancestors = [anc for anc in exc.ancestors()
                                      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('bad-except-order', 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 not is_raising(handler.body)):
-                        self.add_message('broad-except', args=exc.name, node=handler.type)
+                        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:
+                        if has_known_bases(exc):
                             self.add_message('catching-non-exception',
                                              node=handler.type,
                                              args=(exc.name, ))
 
-                exceptions_classes += excs
+                exceptions_classes += [exc for _, exc in 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))