path: root/checkers/classes.py

# Copyright (c) 2003-2006 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.
"""classes checker for Python code
"""
from __future__ import generators

__revision__ = "$Id: classes.py,v 1.77 2006-03-05 14:39:37 syt Exp $"

from logilab import astng

from pylint.interfaces import IASTNGChecker
from pylint.checkers import BaseChecker
from pylint.checkers.utils import overrides_a_method

MSGS = {
##     'F0201': ('Unable to check method %r of interface %s',
##               'Used when PyLint has been unable to fetch a
    ##method declared in \
##               an interface (either in the class or in the
    ##interface) and so to\
##               check its implementation.'),
    'F0202': ('Unable to check methods signature (%s / %s)',
              'Used when PyLint has been unable to check methods signature \
              compatibility for an unexpected raison. Please report this kind \
              if you don\'t make sense of it.'),
##     'F0203': ('Unable to resolve %s',
##               'Used when PyLint has been unable to resolve a name.'),
##     'F0204': ('Name %s has not been resolved to a class as expected',
##               'Used when PyLint try to resolve an ancestor class name but \
##               gets something else than a Class node.'),

##     'E0201': ('Access to undefined member %r',
##               'Used when an instance member not defined in the instance, its\
##               class or its ancestors is accessed.'),
    'E0202': ('An attribute inherited from %s hide this method',
              'Used when a class defines a method which is hiden by an \
              instance attribute from an ancestor class.'),
    'E0203': ('Access to member %r before its definition line %s',
              'Used when an instance member is accessed before it\'s actually\
              assigned.'),
    'W0201': ('Attribute %r defined outside __init__',
              'Used when an instance attribute is defined outside the __init__\
              method.'),
    
    'E0211': ('Method has no argument',
              'Used when a method which should have the bound instance as \
              first argument has no argument defined.'),
    'E0213': ('Method should have "self" as first argument',
              'Used when a method has an attribute different the "self" as\
              first argument.'),
    'C0202': ('Class method should have "cls" as first argument', # E0212
              'Used when a class method has an attribute different than "cls"\
              as first argument, to easily differentiate them from regular \
              instance methods.'),
    'C0203': ('Metaclass method should have "mcs" as first argument', # E0214
              'Used when a metaclass method has an attribute different the \
              "mcs" as first argument.'),
    'W0211': ('Static method with %r as first argument',
              'Used when a static method has "self" or "cls" as first argument.'
              ),
    'R0201': ('Method could be a function',
              'Used when a method doesn\'t use its bound instance, and so could\
              be written as a function.'
              ),
    
    'E0221': ('Interface resolved to %s is not a class',
              'Used when a class claims to implement an interface which is not \
              a class.'),
    'E0222': ('Missing method %r from %s interface' ,
              'Used when a method declared in an interface is missing from a \
              class implementing this interface'),
    'W0221': ('Arguments number differs from %s method',
              'Used when a method has a different number of arguments than in \
              the implemented interface or in an overriden method.'),
    'W0222': ('Signature differs from %s method',
              'Used when a method signature is different than in the \
              implemented interface or in an overriden method.'),
    'W0223': ('Method %r is abstract in class %r but is not overriden',
              'Used when an abstract method (ie raise NotImplementedError) is \
              not overriden in concrete class.'
              ),
    'F0220': ('failed to resolve interfaces implemented by %s (%s)', # W0224
              'Used when a PyLint as failed to find interfaces implemented by \
               a class'),
    
    
    'W0231': ('__init__ method from base class %r is not called',
              'Used when an ancestor class method has an __init__ method \
              which is not called by a derived class.'),
    'W0232': ('Class has no __init__ method',
              'Used when a class has no __init__ method, neither its parent \
              classes.'),
    'W0233': ('__init__ method from a non direct base class %r is called',
              'Used when an __init__ method is called on a class which is not \
              in the direct ancestors for the analysed class.'),
    
    }


class ClassChecker(BaseChecker):
    """checks for :                                                            
    * methods without self as first argument                                   
    * overriden methods signature                                              
    * access only to existant members via self                                 
    * attributes not defined in the __init__ method                            
    * supported interfaces implementation                                      
    * unreachable code                                                         
    """
    
    __implements__ = (IASTNGChecker,)

    # configuration section name
    name = 'classes'
    # messages
    msgs = MSGS
    priority = -2
    # configuration options
    options = (('ignore-iface-methods',
                {'default' : (#zope interface
        'isImplementedBy', 'deferred', 'extends', 'names',
        'namesAndDescriptions', 'queryDescriptionFor',  'getBases',
        'getDescriptionFor', 'getDoc', 'getName', 'getTaggedValue',
        'getTaggedValueTags', 'isEqualOrExtendedBy', 'setTaggedValue',
        'isImplementedByInstancesOf',
        # twisted
        'adaptWith',
        # logilab.common interface
        'is_implemented_by'),
                 'type' : 'csv',
                 'metavar' : '<method names>',
                 'help' : 'List of interface methods to ignore, \
separated by a comma. This is used for instance to not check methods defines \
in Zope\'s Interface base class.'}
                ),
               
               ('defining-attr-methods',
                {'default' : ('__init__', '__new__', 'setUp'),
                 'type' : 'csv',
                 'metavar' : '<method names>',
                 'help' : 'List of method names used to declare (i.e. assign) \
instance attributes.'}
                ),

               )

    def __init__(self, linter=None):
        BaseChecker.__init__(self, linter)
        self._accessed = []
        self._first_attrs = []
        self._meth_could_be_func = None
        
    def visit_class(self, node):
        """init visit variable _accessed and check interfaces
        """        
        self._accessed.append({})
        self._check_bases_classes(node)
        self._check_interfaces(node)
        # if not an interface, exception, metaclass
        if node.type == 'class':
            try:
                node.local_attr('__init__')
            except astng.NotFoundError:
                self.add_message('W0232', args=node, node=node)
            
    def leave_class(self, cnode):
        """close a class node:
        check that instance attributes are defined in __init__ and check
        access to existant members
        """
        # checks attributes are defined in an allowed method such as __init__
        defining_methods = self.config.defining_attr_methods
        for attr, nodes in cnode.instance_attrs.items():
            node = nodes[0] # XXX
            frame = node.frame()
            if frame.name not in defining_methods:
                # check attribute is defined in a parent's __init__
                for parent in cnode.instance_attr_ancestors(attr):
                    frame = parent.instance_attrs[attr][0].frame() # XXX
                    if frame.name in defining_methods:
                        # we're done :)
                        break
                else:
                    # check attribute is defined as a class attribute
                    try:
                        cnode.local_attr(attr)
                    except astng.NotFoundError:
                        self.add_message('W0201', args=attr, node=node)
        # check access to existant members on non metaclass classes
        accessed = self._accessed.pop()
        if cnode.type != 'metaclass':
            self._check_accessed_members(cnode, accessed)
            
    def visit_function(self, node):
        """check method arguments, overriding"""
        # ignore actual functions
        if not node.is_method():
            return
        self._meth_could_be_func = True
        # check first argument is self if this is actually a method 
        klass = node.parent.frame()
        self._check_first_arg_for_type(node, klass.type == 'metaclass')
        if node.name == '__init__':
            self._check_init(node)
            return
        # check signature if the method overrload an herited method
        for overriden in klass.local_attr_ancestors(node.name):
            # get astng for the searched method
            try:
                meth_node = overriden[node.name]
            except KeyError:
                # we have found the method but it's not in the local
                # dictionnary.
                # This may happen with astng build from living objects
                continue
            if not isinstance(meth_node, astng.Function):
                continue
            self._check_signature(node, meth_node, 'overriden')
            break
        # check if the method overload an attribute
        try:
            overriden = klass.instance_attr(node.name)[0] # XXX
            while not isinstance(overriden, astng.Class):
                overriden = overriden.parent.frame()
            self.add_message('E0202', args=overriden.name, node=node)
        except astng.NotFoundError:
            pass
                
    def leave_function(self, node):
        """on method node, check if this method couldn't be a function
        
        ignore class, static and abstract methods, initializer,
        methods overriden from a parent class and any
        kind of method defined in an interface for this warning
        """
        if node.is_method():
            if node.argnames is not None:
                self._first_attrs.pop()
            class_node = node.parent.frame()
            if (self._meth_could_be_func and node.type == 'method'
                and node.name != '__init__'
                and not (node.is_abstract() or
                         overrides_a_method(class_node, node.name))
                and class_node.type != 'interface'):
                self.add_message('R0201', node=node)
                
    def visit_getattr(self, node):
        """check if the name handle an access to a class member
        if so, register it
        """
        if self._first_attrs and isinstance(node.expr, astng.Name) and \
               node.expr.name == self._first_attrs[-1]:                
            self._accessed[-1].setdefault(node.attrname, []).append(node)
                
    def visit_name(self, node):
        """check if the name handle an access to a class member
        if so, register it
        """
        if self._first_attrs and (node.name == self._first_attrs[-1] or
                                  not self._first_attrs[-1]):
            self._meth_could_be_func = False
                
    def _check_accessed_members(self, node, accessed):
        """check that accessed members are defined"""
        # XXX refactor, probably much simpler now that E0201 is in type checker
        for attr, nodes in accessed.items():
##             # is it a builtin attribute ?
##             if attr in ('__dict__', '__class__', '__doc__'):
##                 # FIXME: old class object doesn't have __class__
##                 continue
            # is it a class attribute ?
            try:
                node.local_attr(attr)
                # yes, stop here
                continue
            except astng.NotFoundError:
                pass
            # is it an instance attribute of a parent class ?
            try:
                node.instance_attr_ancestors(attr).next()
                # yes, stop here
                continue
            except StopIteration:
                pass
            # is it an instance attribute ?
            try:
                def_nodes = node.instance_attr(attr) # XXX
                instance_attribute = True
            except astng.NotFoundError:
                instance_attribute = False
            else:
                if len(def_nodes) == 1:
                    def_node = def_nodes[0]
                    # check that if the node is accessed in the same method as
                    # it's defined, it's accessed after the initial assigment
                    frame = def_node.frame()
                    lno = def_node.source_line()
                    for _node in nodes:
                        if _node.frame() is frame and _node.lineno < lno:
                            self.add_message('E0203', node=_node,
                                             args=(attr, lno))
        
    def _check_first_arg_for_type(self, node, metaclass=0):
        """check the name of first argument, expect:
        
        * 'self' for a regular method
        * 'cls' for a class method
        * 'mcs' for a metaclass
        * not one of the above for a static method
        """
        # don't care about functions with unknown argument (builtins)
        if node.argnames is None:
            return
        self._first_attrs.append(node.argnames and node.argnames[0])
        # static method
        if node.type == 'staticmethod':
            if node.argnames and node.argnames[0] in ('self', 'cls', 'mcs'):
                self.add_message('W0211', args=node.argnames[0], node=node)
            self._first_attrs[-1] = None
        # class / regular method with no args
        elif not node.argnames:
            self.add_message('E0211', node=node)
        # metaclass method
        elif metaclass:
            if self._first_attrs[-1] != 'mcs':
                self.add_message('C0203', node=node)
        # class method
        elif node.type == 'classmethod':
            if self._first_attrs[-1] != 'cls':
                self.add_message('C0202', node=node)
        # regular method without self as argument
        elif self._first_attrs[-1] != 'self':
            self.add_message('E0213', node=node)

    def _check_bases_classes(self, node):
        """check that the given class node implements abstract methods from
        base classes
        """
        for method in node.methods():
            owner = method.parent.frame()
            if owner is node: 
                continue
            # owner is not this class, it must be a parent class
            # check that the ancestor's method is not abstract
            if method.is_abstract(pass_is_abstract=False):
                self.add_message('W0223', node=node,
                                 args=(method.name, owner.name))
                    
    def _check_interfaces(self, node):
        """check that the given class node really implements declared
        interfaces
        """
        e0221_hack = [False]
        def iface_handler(obj):
            """filter interface objects, it should be classes"""
            if not isinstance(obj, astng.Class):
                e0221_hack[0] = True
                self.add_message('E0221', node=node,
                                 args=(obj.as_string(),))
                return False
            return True
        ignore_iface_methods = self.config.ignore_iface_methods
        try:
            for iface in node.interfaces(handler_func=iface_handler):
                for imethod in iface.methods():
                    name = imethod.name
                    if name.startswith('_') or name in ignore_iface_methods:
                        # don't check method begining with an underscore,
                        # usually belonging to the interface implementation
                        continue
                    # get class method astng
                    try:
                        method = node_method(node, name)
                    except astng.NotFoundError:
                        self.add_message('E0222', args=(name, iface.name),
                                         node=node)
                        continue
                    # ignore inherited methods
                    if method.parent.frame() is not node:
                        continue
                    # check signature
                    self._check_signature(method, imethod,
                                         '%s interface' % iface.name)
        except astng.InferenceError:
            if e0221_hack[0]:
                return
            implements = astng.Instance(node).getattr('__implements__')[0]
            assignment = implements.parent
            assert isinstance(assignment, astng.Assign)
            # assignment.expr can be a Name or a Tupe or whatever.
            # Use as_string() for the message
            # FIXME: in case of multiple interfaces, find which one could not
            #        be resolved
            self.add_message('F0220', node=implements,
                             args=(node.name, assignment.expr.as_string()))

    def _check_init(self, node):
        """check that the __init__ method call super or ancestors'__init__
        method
        """
        klass_node = node.parent.frame()        
        to_call = _ancestors_to_call(klass_node)
        for stmt in node.nodes_of_class(astng.CallFunc):
            expr = stmt.node
            if not isinstance(expr, astng.Getattr) \
                   or expr.attrname != '__init__':
                continue
            # skip the test if using super
            if isinstance(expr.expr, astng.CallFunc) and \
               isinstance(expr.expr.node, astng.Name) and \
               expr.expr.node.name == 'super':
                return
            try:
                klass = expr.expr.infer().next()
                try:
                    del to_call[klass]
                except KeyError:
                    self.add_message('W0233', node=expr, args=klass.name)
            except astng.InferenceError, ex:
                continue
        for klass in to_call.keys():
            if klass.name == 'object':
                continue
            self.add_message('W0231', args=klass.name, node=node)

    def _check_signature(self, method1, method2, class_type):
        """check that the signature of the two given methods match
        
        class_type is in 'class', 'interface'
        """
        if not (isinstance(method1, astng.Function)
                and isinstance(method2, astng.Function)):
            self.add_message('F0202', args=(method1, method2), node=method1)
            return
        # don't care about functions with unknown argument (builtins)
        if method1.argnames is None or method2.argnames is None:
            return
        if len(method1.argnames) != len(method2.argnames):
            self.add_message('W0221', args=class_type, node=method1)
        elif len(method1.defaults) != len(method2.defaults):
            self.add_message('W0222', args=class_type, node=method1)

                        
def _ancestors_to_call(klass_node, method='__init__'):
    """return a dictionary where keys are the list of base classes providing
    the queried method, and so that should/may be called from the method node
    """
    to_call = {}
    for base_node in klass_node.ancestors(recurs=False):
        try:
            base_node.local_attr(method)
            to_call[base_node] = 1
        except astng.NotFoundError:
            continue
    return to_call
        

def node_method(node, method_name):
    """get astng for <method_name> on the given class node, ensuring it
    is a Function node
    """
    stmt = node.local_attr(method_name)
    if not isinstance(stmt, astng.Function):
        raise astng.NotFoundError(method_name)
    return stmt
        
def register(linter):
    """required method to auto register this checker """
    linter.register_checker(ClassChecker(linter))