arguments-differ understand differences between various type of functions.

This patch improves the way how arguments-differ understands the differences
between classmethods, staticmethods and properties. Closes issue #548.

5 files changed, 171 insertions, 44 deletions

diff --git a/ChangeLog b/ChangeLog
index e6204fc..5a6610f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -159,6 +159,10 @@ ChangeLog for Pylint
       an unary operand is used on something which doesn't support that
       operation (for instance, using the unary bitwise inversion operator
       on an instance which doesn't implement __invert__).
+
+    * Take in consideration differences between arguments of various
+      type of functions (classmethods, staticmethods, properties)
+      when checking for `arguments-differ`. Closes issue #548.
       
 
 
diff --git a/pylint/checkers/classes.py b/pylint/checkers/classes.py
index 4dc00fe..6597602 100644
--- a/pylint/checkers/classes.py
+++ b/pylint/checkers/classes.py
@@ -25,6 +25,7 @@ from astroid import YES, Instance, are_exclusive, AssAttr, Class
 from astroid.bases import Generator, BUILTINS
 from astroid.exceptions import InconsistentMroError, DuplicateBasesError
 from astroid import objects
+from astroid.scoped_nodes import function_to_method
 
 from pylint.interfaces import IAstroidChecker
 from pylint.checkers import BaseChecker
@@ -43,6 +44,14 @@ else:
     NEXT_METHOD = 'next'
 ITER_METHODS = ('__iter__', '__getitem__')
 
+
+def _get_method_args(method):
+    args = method.args.args
+    if method.type == 'classmethod':
+        return len(args) - 1
+    return len(args)
+    
+
 def _called_in_methods(func, klass, methods):
     """ Check if the func was called in any of the given methods,
     belonging to the *klass*. Returns True if so, False otherwise.
@@ -418,7 +427,7 @@ a metaclass class method.'}
                 continue
             if not isinstance(meth_node, astroid.Function):
                 continue
-            self._check_signature(node, meth_node, 'overridden')
+            self._check_signature(node, meth_node, 'overridden', klass)
             break
         if node.decorators:
             for decorator in node.decorators.nodes:
@@ -832,23 +841,40 @@ a metaclass class method.'}
                 continue
             self.add_message('super-init-not-called', args=klass.name, node=node)
 
-    def _check_signature(self, method1, refmethod, class_type):
+    def _check_signature(self, method1, refmethod, class_type, cls):
         """check that the signature of the two given methods match
-        """
+        """        
         if not (isinstance(method1, astroid.Function)
                 and isinstance(refmethod, astroid.Function)):
             self.add_message('method-check-failed',
                              args=(method1, refmethod), node=method1)
             return
-        # don't care about functions with unknown argument (builtins)
+
+        instance = cls.instanciate_class()
+        method1 = function_to_method(method1, instance)
+        refmethod = function_to_method(refmethod, instance)
+
+        # Don't care about functions with unknown argument (builtins).
         if method1.args.args is None or refmethod.args.args is None:
             return
-        # if we use *args, **kwargs, skip the below checks
+        # If we use *args, **kwargs, skip the below checks.
         if method1.args.vararg or method1.args.kwarg:
             return
+        # Ignore private to class methods.
         if is_attr_private(method1.name):
             return
-        if len(method1.args.args) != len(refmethod.args.args):
+        # Ignore setters, they have an implicit extra argument,
+        # which shouldn't be taken in consideration.
+        if method1.decorators:
+            for decorator in method1.decorators.nodes:
+                if (isinstance(decorator, astroid.Getattr) and
+                        decorator.attrname == 'setter'):
+                    return
+        
+        method1_args = _get_method_args(method1)
+        refmethod_args = _get_method_args(refmethod)
+
+        if method1_args != refmethod_args:
             self.add_message('arguments-differ',
                              args=(class_type, method1.name),
                              node=method1)
diff --git a/pylint/test/functional/arguments_differ.py b/pylint/test/functional/arguments_differ.py
new file mode 100644
index 0000000..7fa2015
--- /dev/null
+++ b/pylint/test/functional/arguments_differ.py
@@ -0,0 +1,132 @@
+"""Test that we are emitting arguments-differ when the arguments are different."""

+# pylint: disable=missing-docstring, too-few-public-methods

+

+class Parent(object):

+

+    def test(self):

+        pass

+

+

+class Child(Parent):

+

+    def test(self, arg): # [arguments-differ]

+        pass

+

+

+class ParentDefaults(object):

+

+    def test(self, arg=None, barg=None):

+        pass

+

+class ChildDefaults(ParentDefaults):

+

+    def test(self, arg=None): # [arguments-differ]

+        pass

+

+

+class Classmethod(object):

+

+    @classmethod

+    def func(cls, data):

+        return data

+

+    @classmethod

+    def func1(cls):

+        return cls

+

+

+class ClassmethodChild(Classmethod):

+

+    @staticmethod

+    def func(): # [arguments-differ]

+        pass

+

+    @classmethod

+    def func1(cls):

+        return cls()

+

+

+class Builtins(dict):

+    """Ignore for builtins, for which we don't know the number of required args."""

+

+    @classmethod

+    def fromkeys(cls, arg, arg1):

+        pass

+

+

+class Varargs(object):

+

+    def test(self, arg, **kwargs):

+        pass

+

+class VarargsChild(Varargs):

+

+    def test(self, arg):

+        pass

+

+

+class Super(object):

+    def __init__(self):

+        pass

+

+    def __private(self):

+        pass

+

+    def __private2_(self):

+        pass

+

+    def ___private3(self):

+        pass

+

+    def method(self, param):

+        raise NotImplementedError

+

+

+class Sub(Super):

+

+    # pylint: disable=unused-argument

+    def __init__(self, arg):

+        super(Sub, self).__init__()

+

+    def __private(self, arg):

+        pass

+

+    def __private2_(self, arg):

+        pass

+

+    def ___private3(self, arg):

+        pass

+

+    def method(self, param='abc'):

+        pass

+

+

+class Staticmethod(object):

+

+    @staticmethod

+    def func(data):

+        return data

+

+

+class StaticmethodChild(Staticmethod):

+

+    @classmethod

+    def func(cls, data):

+        return data

+

+

+class Property(object):

+

+    @property

+    def close(self):

+        pass

+

+class PropertySetter(Property):

+

+    @property

+    def close(self):

+        pass

+

+    @close.setter

+    def close(self, attr):

+        return attr

diff --git a/pylint/test/functional/arguments_differ.txt b/pylint/test/functional/arguments_differ.txt
new file mode 100644
index 0000000..cec3359
--- /dev/null
+++ b/pylint/test/functional/arguments_differ.txt
@@ -0,0 +1,3 @@
+arguments-differ:12:Child.test:Arguments number differs from overridden 'test' method

+arguments-differ:23:ChildDefaults.test:Arguments number differs from overridden 'test' method

+arguments-differ:41:ClassmethodChild.func:Arguments number differs from overridden 'func' method
\ No newline at end of file
diff --git a/pylint/test/input/func_noerror_classes_meth_signature.py b/pylint/test/input/func_noerror_classes_meth_signature.py
deleted file mode 100644
index 8a0ad3f..0000000
--- a/pylint/test/input/func_noerror_classes_meth_signature.py
+++ /dev/null
@@ -1,38 +0,0 @@
-# pylint: disable=C0111,R0903,W0231
-"""#2485:
-W0222 "Signature differs from overriden method" false positive
-#18772:
-no prototype consistency check for mangled methods
-"""
-__revision__ = 1
-class Super(object):
-    def __init__(self):
-        pass
-
-    def __private(self):
-        pass
-
-    def __private2_(self):
-        pass
-
-    def ___private3(self):
-        pass
-
-    def method(self, param):
-        raise NotImplementedError
-
-class Sub(Super):
-    def __init__(self, arg):
-        pass
-
-    def __private(self, arg):
-        pass
-
-    def __private2_(self, arg):
-        pass
-
-    def ___private3(self, arg):
-        pass
-
-    def method(self, param='abc'):
-        pass