Add pylint to depot_tools.

third_party/pylint/checkers/variables.py

+# Copyright (c) 2003-2011 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.
+"""variables checkers for Python code
+"""
+
+import sys
+from copy import copy
+
+from logilab import astng
+from logilab.astng import are_exclusive, builtin_lookup, ASTNGBuildingException
+
+from pylint.interfaces import IASTNGChecker
+from pylint.checkers import BaseChecker
+from pylint.checkers.utils import (PYMETHODS, is_ancestor_name, is_builtin,
+     is_defined_before, is_error, is_func_default, is_func_decorator,
+     assign_parent, check_messages, is_inside_except, clobber_in_except)
+
+
+def in_for_else_branch(parent, stmt):
+  """Returns True if stmt in inside the else branch for a parent For stmt."""
+  return (isinstance(parent, astng.For) and
+          any(else_stmt.parent_of(stmt) for else_stmt in parent.orelse))
+
+def overridden_method(klass, name):
+    """get overridden method if any"""
+    try:
+        parent = klass.local_attr_ancestors(name).next()
+    except (StopIteration, KeyError):
+        return None
+    try:
+        meth_node = parent[name]
+    except KeyError:
+        # We have found an ancestor defining <name> but it's not in the local
+        # dictionary. This may happen with astng built from living objects.
+        return None
+    if isinstance(meth_node, astng.Function):
+        return meth_node
+    return None
+
+
+MSGS = {
+    'E0601': ('Using variable %r before assignment',
+              'Used when a local variable is accessed before it\'s \
+              assignment.'),
+    'E0602': ('Undefined variable %r',
+              'Used when an undefined variable is accessed.'),
+    'E0611': ('No name %r in module %r',
+              'Used when a name cannot be found in a module.'),
+
+    'W0601': ('Global variable %r undefined at the module level',
+              'Used when a variable is defined through the "global" statement \
+              but the variable is not defined in the module scope.'),
+    'W0602': ('Using global for %r but no assignment is done',
+              'Used when a variable is defined through the "global" statement \
+              but no assignment to this variable is done.'),
+    'W0603': ('Using the global statement', # W0121
+              'Used when you use the "global" statement to update a global \
+              variable. PyLint just try to discourage this \
+              usage. That doesn\'t mean you can not use it !'),
+    'W0604': ('Using the global statement at the module level', # W0103
+              'Used when you use the "global" statement at the module level \
+              since it has no effect'),
+    'W0611': ('Unused import %s',
+              'Used when an imported module or variable is not used.'),
+    'W0612': ('Unused variable %r',
+              'Used when a variable is defined but not used.'),
+    'W0613': ('Unused argument %r',
+              'Used when a function or method argument is not used.'),
+    'W0614': ('Unused import %s from wildcard import',
+              'Used when an imported module or variable is not used from a \
+              \'from X import *\' style import.'),
+
+    'W0621': ('Redefining name %r from outer scope (line %s)',
+              'Used when a variable\'s name hide a name defined in the outer \
+              scope.'),
+    'W0622': ('Redefining built-in %r',
+              'Used when a variable or function override a built-in.'),
+    'W0623': ('Redefining name %r from %s in exception handler',
+              'Used when an exception handler assigns the exception \
+               to an existing name'),
+
+    'W0631': ('Using possibly undefined loop variable %r',
+              'Used when an loop variable (i.e. defined by a for loop or \
+              a list comprehension or a generator expression) is used outside \
+              the loop.'),
+    }
+
+class VariablesChecker(BaseChecker):
+    """checks for
+    * unused variables / imports
+    * undefined variables
+    * redefinition of variable from builtins or from an outer scope
+    * use of variable before assignment
+    """
+
+    __implements__ = IASTNGChecker
+
+    name = 'variables'
+    msgs = MSGS
+    priority = -1
+    options = (
+               ("init-import",
+                {'default': 0, 'type' : 'yn', 'metavar' : '<y_or_n>',
+                 'help' : 'Tells whether we should check for unused import in \
+__init__ files.'}),
+               ("dummy-variables-rgx",
+                {'default': ('_|dummy'),
+                 'type' :'regexp', 'metavar' : '<regexp>',
+                 'help' : 'A regular expression matching the beginning of \
+                  the name of dummy variables (i.e. not used).'}),
+               ("additional-builtins",
+                {'default': (), 'type' : 'csv',
+                 'metavar' : '<comma separated list>',
+                 'help' : 'List of additional names supposed to be defined in \
+builtins. Remember that you should avoid to define new builtins when possible.'
+                 }),
+               )
+    def __init__(self, linter=None):
+        BaseChecker.__init__(self, linter)
+        self._to_consume = None
+        self._checking_mod_attr = None
+        self._vars = None
+
+    def visit_module(self, node):
+        """visit module : update consumption analysis variable
+        checks globals doesn't overrides builtins
+        """
+        self._to_consume = [(copy(node.locals), {}, 'module')]
+        self._vars = []
+        for name, stmts in node.locals.items():
+            if is_builtin(name) and not is_inside_except(stmts[0]):
+                # do not print Redefining builtin for additional builtins
+                self.add_message('W0622', args=name, node=stmts[0])
+
+    @check_messages('W0611', 'W0614')
+    def leave_module(self, node):
+        """leave module: check globals
+        """
+        assert len(self._to_consume) == 1
+        not_consumed = self._to_consume.pop()[0]
+        # don't check unused imports in __init__ files
+        if not self.config.init_import and node.package:
+            return
+        for name, stmts in not_consumed.items():
+            stmt = stmts[0]
+            if isinstance(stmt, astng.Import):
+                self.add_message('W0611', args=name, node=stmt)
+            elif isinstance(stmt, astng.From) and stmt.modname != '__future__':
+                if stmt.names[0][0] == '*':
+                    self.add_message('W0614', args=name, node=stmt)
+                else:
+                    self.add_message('W0611', args=name, node=stmt)
+        del self._to_consume
+        del self._vars
+
+    def visit_class(self, node):
+        """visit class: update consumption analysis variable
+        """
+        self._to_consume.append((copy(node.locals), {}, 'class'))
+
+    def leave_class(self, _):
+        """leave class: update consumption analysis variable
+        """
+        # do not check for not used locals here (no sense)
+        self._to_consume.pop()
+
+    def visit_lambda(self, node):
+        """visit lambda: update consumption analysis variable
+        """
+        self._to_consume.append((copy(node.locals), {}, 'lambda'))
+
+    def leave_lambda(self, _):
+        """leave lambda: update consumption analysis variable
+        """
+        # do not check for not used locals here
+        self._to_consume.pop()
+
+    def visit_genexpr(self, node):
+        """visit genexpr: update consumption analysis variable
+        """
+        self._to_consume.append((copy(node.locals), {}, 'comprehension'))
+
+    def leave_genexpr(self, _):
+        """leave genexpr: update consumption analysis variable
+        """
+        # do not check for not used locals here
+        self._to_consume.pop()
+
+    def visit_dictcomp(self, node):
+        """visit dictcomp: update consumption analysis variable
+        """
+        self._to_consume.append((copy(node.locals), {}, 'comprehension'))
+
+    def leave_dictcomp(self, _):
+        """leave dictcomp: update consumption analysis variable
+        """
+        # do not check for not used locals here
+        self._to_consume.pop()
+
+    def visit_setcomp(self, node):
+        """visit setcomp: update consumption analysis variable
+        """
+        self._to_consume.append((copy(node.locals), {}, 'comprehension'))
+
+    def leave_setcomp(self, _):
+        """leave setcomp: update consumption analysis variable
+        """
+        # do not check for not used locals here
+        self._to_consume.pop()
+
+    def visit_function(self, node):
+        """visit function: update consumption analysis variable and check locals
+        """
+        self._to_consume.append((copy(node.locals), {}, 'function'))
+        self._vars.append({})
+        if not set(('W0621', 'W0622')) & self.active_msgs:
+            return
+        globs = node.root().globals
+        for name, stmt in node.items():
+            if is_inside_except(stmt):
+                continue
+            if name in globs and not isinstance(stmt, astng.Global):
+                line = globs[name][0].lineno
+                self.add_message('W0621', args=(name, line), node=stmt)
+            elif is_builtin(name):
+                # do not print Redefining builtin for additional builtins
+                self.add_message('W0622', args=name, node=stmt)
+
+    def leave_function(self, node):
+        """leave function: check function's locals are consumed"""
+        not_consumed = self._to_consume.pop()[0]
+        self._vars.pop(0)
+        if not set(('W0612', 'W0613')) & self.active_msgs:
+            return
+        # don't check arguments of function which are only raising an exception
+        if is_error(node):
+            return
+        # don't check arguments of abstract methods or within an interface
+        is_method = node.is_method()
+        klass = node.parent.frame()
+        if is_method and (klass.type == 'interface' or node.is_abstract()):
+            return
+        authorized_rgx = self.config.dummy_variables_rgx
+        called_overridden = False
+        argnames = node.argnames()
+        for name, stmts in not_consumed.iteritems():
+            # ignore some special names specified by user configuration
+            if authorized_rgx.match(name):
+                continue
+            # ignore names imported by the global statement
+            # FIXME: should only ignore them if it's assigned latter
+            stmt = stmts[0]
+            if isinstance(stmt, astng.Global):
+                continue
+            # care about functions with unknown argument (builtins)
+            if name in argnames:
+                if is_method:
+                    # don't warn for the first argument of a (non static) method
+                    if node.type != 'staticmethod' and name == argnames[0]:
+                        continue
+                    # don't warn for argument of an overridden method
+                    if not called_overridden:
+                        overridden = overridden_method(klass, node.name)
+                        called_overridden = True
+                    if overridden is not None and name in overridden.argnames():
+                        continue
+                    if node.name in PYMETHODS and node.name not in ('__init__', '__new__'):
+                        continue
+                # don't check callback arguments XXX should be configurable
+                if node.name.startswith('cb_') or node.name.endswith('_cb'):
+                    continue
+                self.add_message('W0613', args=name, node=stmt)
+            else:
+                self.add_message('W0612', args=name, node=stmt)
+
+    @check_messages('W0601', 'W0602', 'W0603', 'W0604', 'W0622')
+    def visit_global(self, node):
+        """check names imported exists in the global scope"""
+        frame = node.frame()
+        if isinstance(frame, astng.Module):
+            self.add_message('W0604', node=node)
+            return
+        module = frame.root()
+        default_message = True
+        for name in node.names:
+            try:
+                assign_nodes = module.getattr(name)
+            except astng.NotFoundError:
+                # unassigned global, skip
+                assign_nodes = []
+            for anode in assign_nodes:
+                if anode.parent is None:
+                    # node returned for builtin attribute such as __file__,
+                    # __doc__, etc...
+                    continue
+                if anode.frame() is frame:
+                    # same scope level assignment
+                    break
+            else:
+                # global but no assignment
+                self.add_message('W0602', args=name, node=node)
+                default_message = False
+            if not assign_nodes:
+                continue
+            for anode in assign_nodes:
+                if anode.parent is None:
+                    self.add_message('W0622', args=name, node=node)
+                    break
+                if anode.frame() is module:
+                    # module level assignment
+                    break
+            else:
+                # global undefined at the module scope
+                self.add_message('W0601', args=name, node=node)
+                default_message = False
+        if default_message:
+            self.add_message('W0603', node=node)
+
+    def _loopvar_name(self, node, name):
+        # filter variables according to node's scope
+        # XXX used to filter parents but don't remember why, and removing this
+        # fixes a W0631 false positive reported by Paul Hachmann on 2008/12 on
+        # python-projects (added to func_use_for_or_listcomp_var test)
+        #astmts = [stmt for stmt in node.lookup(name)[1]
+        #          if hasattr(stmt, 'ass_type')] and
+        #          not stmt.statement().parent_of(node)]
+        if 'W0631' not in self.active_msgs:
+            return
+        astmts = [stmt for stmt in node.lookup(name)[1]
+                  if hasattr(stmt, 'ass_type')]
+        # filter variables according their respective scope test is_statement
+        # and parent to avoid #74747. This is not a total fix, which would
+        # introduce a mechanism similar to special attribute lookup in
+        # modules. Also, in order to get correct inference in this case, the
+        # scope lookup rules would need to be changed to return the initial
+        # assignment (which does not exist in code per se) as well as any later
+        # modifications.
+        if not astmts or (astmts[0].is_statement or astmts[0].parent) \
+             and astmts[0].statement().parent_of(node):
+            _astmts = []
+        else:
+            _astmts = astmts[:1]
+        for i, stmt in enumerate(astmts[1:]):
+            if (astmts[i].statement().parent_of(stmt)
+                and not in_for_else_branch(astmts[i].statement(), stmt)):
+                continue
+            _astmts.append(stmt)
+        astmts = _astmts
+        if len(astmts) == 1:
+            ass = astmts[0].ass_type()
+            if isinstance(ass, (astng.For, astng.Comprehension, astng.GenExpr)) \
+                   and not ass.statement() is node.statement():
+                self.add_message('W0631', args=name, node=node)
+
+    def visit_excepthandler(self, node):
+        clobbering, args = clobber_in_except(node.name)
+        if clobbering:
+            self.add_message('W0623', args=args, node=node)
+
+    def visit_assname(self, node):
+        if isinstance(node.ass_type(), astng.AugAssign):
+            self.visit_name(node)
+
+    def visit_delname(self, node):
+        self.visit_name(node)
+
+    def visit_name(self, node):
+        """check that a name is defined if the current scope and doesn't
+        redefine a built-in
+        """
+        stmt = node.statement()
+        if stmt.fromlineno is None:
+            # name node from a astng built from live code, skip
+            assert not stmt.root().file.endswith('.py')
+            return
+        name = node.name
+        frame = stmt.scope()
+        # if the name node is used as a function default argument's value or as
+        # a decorator, then start from the parent frame of the function instead
+        # of the function frame - and thus open an inner class scope
+        if (is_func_default(node) or is_func_decorator(node)
+            or is_ancestor_name(frame, node)):
+            start_index = len(self._to_consume) - 2
+        else:
+            start_index = len(self._to_consume) - 1
+        # iterates through parent scopes, from the inner to the outer
+        base_scope_type = self._to_consume[start_index][-1]
+        for i in range(start_index, -1, -1):
+            to_consume, consumed, scope_type = self._to_consume[i]
+            # if the current scope is a class scope but it's not the inner
+            # scope, ignore it. This prevents to access this scope instead of
+            # the globals one in function members when there are some common
+            # names. The only exception is when the starting scope is a
+            # comprehension and its direct outer scope is a class
+            if scope_type == 'class' and i != start_index and not (
+                base_scope_type == 'comprehension' and i == start_index-1):
+                # XXX find a way to handle class scope in a smoother way
+                continue
+            # the name has already been consumed, only check it's not a loop
+            # variable used outside the loop
+            if name in consumed:
+                self._loopvar_name(node, name)
+                break
+            # mark the name as consumed if it's defined in this scope
+            # (i.e. no KeyError is raised by "to_consume[name]")
+            try:
+                consumed[name] = to_consume[name]
+            except KeyError:
+                continue
+            # checks for use before assignment
+            defnode = assign_parent(to_consume[name][0])
+            if defnode is not None:
+                defstmt = defnode.statement()
+                defframe = defstmt.frame()
+                maybee0601 = True
+                if not frame is defframe:
+                    maybee0601 = False
+                elif defframe.parent is None:
+                    # we are at the module level, check the name is not
+                    # defined in builtins
+                    if name in defframe.scope_attrs or builtin_lookup(name)[1]:
+                        maybee0601 = False
+                else:
+                    # we are in a local scope, check the name is not
+                    # defined in global or builtin scope
+                    if defframe.root().lookup(name)[1]:
+                        maybee0601 = False
+                if (maybee0601
+                    and stmt.fromlineno <= defstmt.fromlineno
+                    and not is_defined_before(node)
+                    and not are_exclusive(stmt, defstmt, ('NameError', 'Exception', 'BaseException'))):
+                    if defstmt is stmt and isinstance(node, (astng.DelName,
+                                                             astng.AssName)):
+                        self.add_message('E0602', args=name, node=node)
+                    elif self._to_consume[-1][-1] != 'lambda':
+                        # E0601 may *not* occurs in lambda scope
+                        self.add_message('E0601', args=name, node=node)
+            if not isinstance(node, astng.AssName): # Aug AssName
+                del to_consume[name]
+            else:
+                del consumed[name]
+            # check it's not a loop variable used outside the loop
+            self._loopvar_name(node, name)
+            break
+        else:
+            # we have not found the name, if it isn't a builtin, that's an
+            # undefined name !
+            if not (name in astng.Module.scope_attrs or is_builtin(name)
+                    or name in self.config.additional_builtins):
+                self.add_message('E0602', args=name, node=node)
+
+    @check_messages('E0611')
+    def visit_import(self, node):
+        """check modules attribute accesses"""
+        for name, _ in node.names:
+            parts = name.split('.')
+            try:
+                module = node.infer_name_module(parts[0]).next()
+            except astng.ResolveError:
+                continue
+            self._check_module_attrs(node, module, parts[1:])
+
+    @check_messages('E0611')
+    def visit_from(self, node):
+        """check modules attribute accesses"""
+        name_parts = node.modname.split('.')
+        level = getattr(node, 'level', None)
+        try:
+            module = node.root().import_module(name_parts[0], level=level)
+        except ASTNGBuildingException:
+            return
+        except Exception, exc:
+            print 'Unhandled exception in VariablesChecker:', exc
+            return
+        module = self._check_module_attrs(node, module, name_parts[1:])
+        if not module:
+            return
+        for name, _ in node.names:
+            if name == '*':
+                continue
+            self._check_module_attrs(node, module, name.split('.'))
+
+    def _check_module_attrs(self, node, module, module_names):
+        """check that module_names (list of string) are accessible through the
+        given module
+        if the latest access name corresponds to a module, return it
+        """
+        assert isinstance(module, astng.Module), module
+        while module_names:
+            name = module_names.pop(0)
+            if name == '__dict__':
+                module = None
+                break
+            try:
+                module = module.getattr(name)[0].infer().next()
+                if module is astng.YES:
+                    return None
+            except astng.NotFoundError:
+                self.add_message('E0611', args=(name, module.name), node=node)
+                return None
+            except astng.InferenceError:
+                return None
+        if module_names:
+            # FIXME: other message if name is not the latest part of
+            # module_names ?
+            modname = module and module.name or '__dict__'
+            self.add_message('E0611', node=node,
+                             args=('.'.join(module_names), modname))
+            return None
+        if isinstance(module, astng.Module):
+            return module
+        return None
+
+
+class VariablesChecker3k(VariablesChecker):
+    '''Modified variables checker for 3k'''
+    # listcomp have now also their scope
+
+    def visit_listcomp(self, node):
+        """visit dictcomp: update consumption analysis variable
+        """
+        self._to_consume.append((copy(node.locals), {}, 'comprehension'))
+
+    def leave_listcomp(self, _):
+        """leave dictcomp: update consumption analysis variable
+        """
+        # do not check for not used locals here
+        self._to_consume.pop()
+
+if sys.version_info >= (3, 0):
+    VariablesChecker = VariablesChecker3k
+
+
+def register(linter):
+    """required method to auto register this checker"""
+    linter.register_checker(VariablesChecker(linter))