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370 lines
16 KiB
Python
370 lines
16 KiB
Python
# Copyright (c) 2003-2013 LOGILAB S.A. (Paris, FRANCE).
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# http://www.logilab.fr/ -- mailto:contact@logilab.fr
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# This program is free software; you can redistribute it and/or modify it under
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# the terms of the GNU General Public License as published by the Free Software
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# Foundation; either version 2 of the License, or (at your option) any later
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# version.
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#
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# This program is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License along with
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# this program; if not, write to the Free Software Foundation, Inc.,
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# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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"""exceptions handling (raising, catching, exceptions classes) checker
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"""
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import inspect
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import sys
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import six
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from six.moves import builtins
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import astroid
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from pylint.checkers import BaseChecker
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from pylint.checkers.utils import (
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is_raising,
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check_messages,
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inherit_from_std_ex,
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EXCEPTIONS_MODULE,
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safe_infer,
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has_known_bases)
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from pylint.interfaces import IAstroidChecker
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def _builtin_exceptions():
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def predicate(obj):
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return isinstance(obj, type) and issubclass(obj, BaseException)
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members = inspect.getmembers(six.moves.builtins, predicate)
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return {exc.__name__ for (_, exc) in members}
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def _annotated_unpack_infer(stmt, context=None):
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"""
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Recursively generate nodes inferred by the given statement.
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If the inferred value is a list or a tuple, recurse on the elements.
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Returns an iterator which yields tuples in the format
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('original node', 'infered node').
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"""
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if isinstance(stmt, (astroid.List, astroid.Tuple)):
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for elt in stmt.elts:
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inferred = safe_infer(elt)
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if inferred and inferred is not astroid.YES:
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yield elt, inferred
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return
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for infered in stmt.infer(context):
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if infered is astroid.YES:
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continue
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yield stmt, infered
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PY3K = sys.version_info >= (3, 0)
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OVERGENERAL_EXCEPTIONS = ('Exception',)
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BUILTINS_NAME = builtins.__name__
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MSGS = {
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'E0701': ('Bad except clauses order (%s)',
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'bad-except-order',
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'Used when except clauses are not in the correct order (from the '
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'more specific to the more generic). If you don\'t fix the order, '
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'some exceptions may not be catched by the most specific handler.'),
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'E0702': ('Raising %s while only classes or instances are allowed',
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'raising-bad-type',
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'Used when something which is neither a class, an instance or a \
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string is raised (i.e. a `TypeError` will be raised).'),
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'E0703': ('Exception context set to something which is not an '
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'exception, nor None',
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'bad-exception-context',
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'Used when using the syntax "raise ... from ...", '
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'where the exception context is not an exception, '
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'nor None.',
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{'minversion': (3, 0)}),
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'E0704': ('The raise statement is not inside an except clause',
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'misplaced-bare-raise',
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'Used when a bare raise is not used inside an except clause. '
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'This generates an error, since there are no active exceptions '
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'to be reraised. An exception to this rule is represented by '
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'a bare raise inside a finally clause, which might work, as long '
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'as an exception is raised inside the try block, but it is '
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'nevertheless a code smell that must not be relied upon.'),
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'E0710': ('Raising a new style class which doesn\'t inherit from BaseException',
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'raising-non-exception',
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'Used when a new style class which doesn\'t inherit from \
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BaseException is raised.'),
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'E0711': ('NotImplemented raised - should raise NotImplementedError',
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'notimplemented-raised',
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'Used when NotImplemented is raised instead of \
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NotImplementedError'),
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'E0712': ('Catching an exception which doesn\'t inherit from BaseException: %s',
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'catching-non-exception',
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'Used when a class which doesn\'t inherit from \
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BaseException is used as an exception in an except clause.'),
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'W0702': ('No exception type(s) specified',
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'bare-except',
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'Used when an except clause doesn\'t specify exceptions type to \
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catch.'),
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'W0703': ('Catching too general exception %s',
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'broad-except',
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'Used when an except catches a too general exception, \
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possibly burying unrelated errors.'),
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'W0705': ('Catching previously caught exception type %s',
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'duplicate-except',
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'Used when an except catches a type that was already caught by '
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'a previous handler.'),
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'W0710': ('Exception doesn\'t inherit from standard "Exception" class',
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'nonstandard-exception',
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'Used when a custom exception class is raised but doesn\'t \
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inherit from the builtin "Exception" class.',
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{'maxversion': (3, 0)}),
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'W0711': ('Exception to catch is the result of a binary "%s" operation',
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'binary-op-exception',
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'Used when the exception to catch is of the form \
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"except A or B:". If intending to catch multiple, \
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rewrite as "except (A, B):"'),
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}
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class ExceptionsChecker(BaseChecker):
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"""checks for
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* excepts without exception filter
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* type of raise argument : string, Exceptions, other values
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"""
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__implements__ = IAstroidChecker
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name = 'exceptions'
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msgs = MSGS
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priority = -4
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options = (('overgeneral-exceptions',
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{'default' : OVERGENERAL_EXCEPTIONS,
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'type' :'csv', 'metavar' : '<comma-separated class names>',
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'help' : 'Exceptions that will emit a warning '
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'when being caught. Defaults to "%s"' % (
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', '.join(OVERGENERAL_EXCEPTIONS),)}
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),
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)
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def open(self):
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self.builtin_exceptions = _builtin_exceptions()
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super(ExceptionsChecker, self).open()
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@check_messages('nonstandard-exception', 'misplaced-bare-raise',
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'raising-bad-type', 'raising-non-exception',
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'notimplemented-raised', 'bad-exception-context')
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def visit_raise(self, node):
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"""visit raise possibly inferring value"""
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if node.exc is None:
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self._check_misplaced_bare_raise(node)
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return
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if PY3K and node.cause:
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self._check_bad_exception_context(node)
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expr = node.exc
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if self._check_raise_value(node, expr):
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return
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else:
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try:
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value = next(astroid.unpack_infer(expr))
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except astroid.InferenceError:
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return
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self._check_raise_value(node, value)
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def _check_misplaced_bare_raise(self, node):
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# Filter out if it's present in __exit__.
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scope = node.scope()
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if (isinstance(scope, astroid.FunctionDef)
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and scope.is_method()
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and scope.name == '__exit__'):
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return
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current = node
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# Stop when a new scope is generated or when the raise
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# statement is found inside a TryFinally.
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ignores = (astroid.ExceptHandler, astroid.FunctionDef, astroid.TryFinally)
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while current and not isinstance(current.parent, ignores):
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current = current.parent
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expected = (astroid.ExceptHandler,)
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if (not current
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or not isinstance(current.parent, expected)):
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self.add_message('misplaced-bare-raise', node=node)
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def _check_bad_exception_context(self, node):
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"""Verify that the exception context is properly set.
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An exception context can be only `None` or an exception.
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"""
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cause = safe_infer(node.cause)
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if cause in (astroid.YES, None):
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return
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if isinstance(cause, astroid.Const):
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if cause.value is not None:
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self.add_message('bad-exception-context',
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node=node)
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elif (not isinstance(cause, astroid.ClassDef) and
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not inherit_from_std_ex(cause)):
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self.add_message('bad-exception-context',
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node=node)
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def _check_raise_value(self, node, expr):
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"""check for bad values, string exception and class inheritance
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"""
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value_found = True
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if isinstance(expr, astroid.Const):
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value = expr.value
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if not isinstance(value, str):
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# raising-string will be emitted from python3 porting checker.
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self.add_message('raising-bad-type', node=node,
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args=value.__class__.__name__)
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elif ((isinstance(expr, astroid.Name) and
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expr.name in ('None', 'True', 'False')) or
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isinstance(expr, (astroid.List, astroid.Dict, astroid.Tuple,
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astroid.Module, astroid.FunctionDef))):
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emit = True
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if not PY3K and isinstance(expr, astroid.Tuple) and expr.elts:
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# On Python 2, using the following is not an error:
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# raise (ZeroDivisionError, None)
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# raise (ZeroDivisionError, )
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# What's left to do is to check that the first
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# argument is indeed an exception.
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# Verifying the other arguments is not
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# the scope of this check.
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first = expr.elts[0]
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inferred = safe_infer(first)
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if isinstance(inferred, astroid.Instance):
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# pylint: disable=protected-access
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inferred = inferred._proxied
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if (inferred is astroid.YES or
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isinstance(inferred, astroid.ClassDef)
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and inherit_from_std_ex(inferred)):
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emit = False
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if emit:
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self.add_message('raising-bad-type',
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node=node,
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args=expr.name)
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elif ((isinstance(expr, astroid.Name) and expr.name == 'NotImplemented')
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or (isinstance(expr, astroid.Call) and
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isinstance(expr.func, astroid.Name) and
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expr.func.name == 'NotImplemented')):
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self.add_message('notimplemented-raised', node=node)
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elif isinstance(expr, (astroid.Instance, astroid.ClassDef)):
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if isinstance(expr, astroid.Instance):
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# pylint: disable=protected-access
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expr = expr._proxied
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if (isinstance(expr, astroid.ClassDef) and
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not inherit_from_std_ex(expr) and
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has_known_bases(expr)):
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if expr.newstyle:
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self.add_message('raising-non-exception', node=node)
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else:
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self.add_message('nonstandard-exception', node=node)
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else:
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value_found = False
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else:
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value_found = False
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return value_found
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def _check_catching_non_exception(self, handler, exc, part):
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if isinstance(exc, astroid.Tuple):
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# Check if it is a tuple of exceptions.
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inferred = [safe_infer(elt) for elt in exc.elts]
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if any(node is astroid.YES for node in inferred):
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# Don't emit if we don't know every component.
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return
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if all(node and inherit_from_std_ex(node)
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for node in inferred):
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return
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if not isinstance(exc, astroid.ClassDef):
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# Don't emit the warning if the infered stmt
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# is None, but the exception handler is something else,
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# maybe it was redefined.
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if (isinstance(exc, astroid.Const) and
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exc.value is None):
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if ((isinstance(handler.type, astroid.Const) and
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handler.type.value is None) or
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handler.type.parent_of(exc)):
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# If the exception handler catches None or
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# the exception component, which is None, is
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# defined by the entire exception handler, then
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# emit a warning.
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self.add_message('catching-non-exception',
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node=handler.type,
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args=(part.as_string(), ))
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else:
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self.add_message('catching-non-exception',
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node=handler.type,
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args=(part.as_string(), ))
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return
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if (not inherit_from_std_ex(exc) and
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exc.name not in self.builtin_exceptions):
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if has_known_bases(exc):
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self.add_message('catching-non-exception',
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node=handler.type,
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args=(exc.name, ))
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@check_messages('bare-except', 'broad-except',
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'binary-op-exception', 'bad-except-order',
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'catching-non-exception', 'duplicate-except')
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def visit_tryexcept(self, node):
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"""check for empty except"""
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exceptions_classes = []
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nb_handlers = len(node.handlers)
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for index, handler in enumerate(node.handlers):
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if handler.type is None:
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if not is_raising(handler.body):
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self.add_message('bare-except', node=handler)
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# check if a "except:" is followed by some other
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# except
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if index < (nb_handlers - 1):
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msg = 'empty except clause should always appear last'
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self.add_message('bad-except-order', node=node, args=msg)
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elif isinstance(handler.type, astroid.BoolOp):
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self.add_message('binary-op-exception',
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node=handler, args=handler.type.op)
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else:
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try:
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excs = list(_annotated_unpack_infer(handler.type))
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except astroid.InferenceError:
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continue
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for part, exc in excs:
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if exc is astroid.YES:
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continue
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if (isinstance(exc, astroid.Instance)
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and inherit_from_std_ex(exc)):
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# pylint: disable=protected-access
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exc = exc._proxied
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self._check_catching_non_exception(handler, exc, part)
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if not isinstance(exc, astroid.ClassDef):
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continue
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exc_ancestors = [anc for anc in exc.ancestors()
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if isinstance(anc, astroid.ClassDef)]
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for previous_exc in exceptions_classes:
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if previous_exc in exc_ancestors:
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msg = '%s is an ancestor class of %s' % (
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previous_exc.name, exc.name)
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self.add_message('bad-except-order',
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node=handler.type, args=msg)
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if (exc.name in self.config.overgeneral_exceptions
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and exc.root().name == EXCEPTIONS_MODULE
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and not is_raising(handler.body)):
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self.add_message('broad-except',
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args=exc.name, node=handler.type)
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if exc in exceptions_classes:
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self.add_message('duplicate-except',
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args=exc.name, node=handler.type)
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exceptions_classes += [exc for _, exc in excs]
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def register(linter):
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"""required method to auto register this checker"""
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linter.register_checker(ExceptionsChecker(linter))
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