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168 lines
7.1 KiB
Python
168 lines
7.1 KiB
Python
# 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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# 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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""" Copyright (c) 2003-2005 LOGILAB S.A. (Paris, FRANCE).
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http://www.logilab.fr/ -- mailto:contact@logilab.fr
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exceptions checkers for Python code
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"""
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__revision__ = '$Id: exceptions.py,v 1.27 2006-03-08 15:53:42 syt Exp $'
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from logilab.common.compat import enumerate
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from logilab import astng
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from logilab.astng.inference import unpack_infer
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from pylint.checkers import BaseChecker
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from pylint.checkers.utils import is_empty
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from pylint.interfaces import IASTNGChecker
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MSGS = {
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'E0701': (
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'Bad except clauses order (%s)',
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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, instances or string are allowed',
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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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'W0701': ('Raising a string exception',
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'Used when a string exception is raised.'),
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'W0702': ('No exception\'s type specified',
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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': ('Catch "Exception"',
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'Used when an except catch Exception instances.'),
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'W0704': ('Except doesn\'t do anything',
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'Used when an except clause does nothing but "pass" and there is\
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no "else" clause.'),
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'W0706': (
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'Identifier %s used to raise an exception is assigned to %s',
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'Used when a variable used to raise an exception is initially \
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assigned to a value which can\'t be used as an exception.'),
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}
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def is_raising(stmt):
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"""return true if the given statement node raise an exception
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"""
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for node in stmt.nodes:
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if isinstance(node, astng.Raise):
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return 1
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return 0
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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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* string exceptions
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"""
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__implements__ = IASTNGChecker
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name = 'exceptions'
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msgs = MSGS
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priority = -4
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options = ()
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def visit_raise(self, node):
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"""check for string exception
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"""
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# ignore empty raise
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if node.expr1 is None:
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return
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expr = node.expr1
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if isinstance(expr, astng.Const):
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value = expr.value
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if isinstance(value, str):
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self.add_message('W0701', node=node)
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else:
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self.add_message('E0702', node=node,
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args=value.__class__.__name__)
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elif isinstance(expr, astng.Name) and \
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expr.name in ('None', 'True', 'False'):
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self.add_message('E0702', node=node, args=expr.name)
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elif isinstance(expr, astng.Mod):
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self.add_message('W0701', node=node)
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else:
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try:
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value = unpack_infer(expr).next()
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except astng.InferenceError:
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return
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if value is astng.YES:
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return
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# must to be carefull since Const, Dict, .. inherit from
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# Instance now
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if isinstance(value, (astng.Class, astng.Module)):
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return
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if isinstance(value, astng.Instance) and \
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isinstance(value._proxied, astng.Class):
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return
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if isinstance(value, astng.Const) and \
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(value.value is None or
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value.value is True or value.value is False):
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# this Const has been generated by resolve
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# since None, True and False are represented by Name
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# nodes in the ast, and so this const node doesn't
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# have the necessary parent, lineno and so on attributes
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assinfo = value.as_string()
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else:
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assinfo = '%s line %s' % (value.as_string(),
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value.source_line())
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self.add_message('W0706', node=node,
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args=(expr.as_string(), assinfo))
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def visit_tryexcept(self, node):
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"""check for empty except
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"""
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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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exc_type = handler[0]
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stmt = handler[2]
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# single except doing nothing but "pass" without else clause
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if nb_handlers == 1 and is_empty(stmt) and not node.else_:
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self.add_message('W0704', node=exc_type)
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if exc_type is None:
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if nb_handlers == 1 and not is_raising(stmt):
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self.add_message('W0702', node=stmt.nodes[0])
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# check if a "except:" is followed by some other
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# except
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elif index < (nb_handlers - 1):
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msg = 'empty except clause should always appears last'
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self.add_message('E0701', node=node, args=msg)
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else:
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try:
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excs = list(unpack_infer(exc_type))
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except astng.InferenceError:
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continue
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for exc in excs:
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if exc is astng.YES:
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continue
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if not isinstance(exc, astng.Class):
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continue # XXX
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exc_ancestors = [anc for anc in exc.ancestors()
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if isinstance(anc, astng.Class)]
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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('E0701', node=exc_type, args=msg)
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if (exc.name == 'Exception'
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and exc.root().name == 'exceptions'
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and nb_handlers == 1 and not is_raising(stmt)):
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self.add_message('W0703', node=exc_type)
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exceptions_classes += 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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