Add support for abc.ABC from Python 3.4.

3 files changed, 77 insertions, 2 deletions

diff --git a/checkers/base.py b/checkers/base.py
index b16377a..98f85d8 100644
--- a/checkers/base.py
+++ b/checkers/base.py
@@ -145,6 +145,13 @@ def decorated_with_abc(func):
             if infered and infered.qname() in ABC_METHODS:
                 return True
 
+def has_abstract_methods(node):
+    """ Determine if the given `node` has
+    abstract methods, defined with `abc` module.
+    """
+    return any(decorated_with_abc(meth)
+               for meth in node.mymethods())
+
 def report_by_type_stats(sect, stats, old_stats):
     """make a report of
 
@@ -349,12 +356,22 @@ class BasicErrorChecker(_BasicChecker):
         # __init__ was called
         metaclass = infered.metaclass()
         if metaclass is None:
+            # Python 3.4 has `abc.ABC`, which won't be detected
+            # by ClassNode.metaclass()
+            for ancestor in infered.ancestors():
+                if (ancestor.name == 'ABC' and
+                    ancestor.parent and
+                    ancestor.parent.name == 'abc' and
+                    has_abstract_methods(infered)):
+
+                    self.add_message('abstract-class-instantiated', node=node)
+                    break
             return
         if (metaclass.name == 'ABCMeta' and
             metaclass.parent and
             metaclass.parent.name == 'abc' and
-            any(decorated_with_abc(meth)
-                for meth in infered.mymethods())):
+            has_abstract_methods(infered)):
+
             self.add_message('abstract-class-instantiated', node=node)
    
     def _check_else_on_loop(self, node):
diff --git a/test/input/func_abstract_class_instantiated_py34.py b/test/input/func_abstract_class_instantiated_py34.py
new file mode 100644
index 0000000..1814f34
--- /dev/null
+++ b/test/input/func_abstract_class_instantiated_py34.py
@@ -0,0 +1,55 @@
+"""Check that instantiating a class with
+`abc.ABCMeta` as metaclass fails if it defines
+abstract methods.
+"""
+
+# pylint: disable=too-few-public-methods, missing-docstring, abstract-class-not-used, no-init
+
+__revision__ = 0
+
+import abc
+

+class GoodClass(object, metaclass=abc.ABCMeta):

+    pass

+

+class SecondGoodClass(object, metaclass=abc.ABCMeta):

+    def test(self):

+        """ do nothing. """

+        pass

+

+class ThirdGoodClass(object, metaclass=abc.ABCMeta):

+    """ This should not raise the warning. """

+    def test(self):

+        raise NotImplementedError()

+

+class FourthGoodClass(abc.ABC):

+    """ Neither this. """

+    def test(self):

+        pass

+

+class BadClass(object, metaclass=abc.ABCMeta):

+    @abc.abstractmethod

+    def test(self):

+        """ do nothing. """

+        pass

+

+class SecondBadClass(object, metaclass=abc.ABCMeta):

+    @property

+    @abc.abstractmethod

+    def test(self):

+        """ do nothing. """

+

+class ThirdBadClass(abc.ABC):

+    @abc.abstractmethod

+    def test(self):

+        pass

+

+def main():

+    """ do nothing """

+    GoodClass()

+    SecondGoodClass()

+    ThirdGoodClass()

+    FourthGoodClass()

+    BadClass()

+    SecondBadClass()

+    ThirdBadClass()

diff --git a/test/messages/func_abstract_class_instantiated_py34.txt b/test/messages/func_abstract_class_instantiated_py34.txt
new file mode 100644
index 0000000..310f8ea
--- /dev/null
+++ b/test/messages/func_abstract_class_instantiated_py34.txt
@@ -0,0 +1,3 @@
+E: 53:main: Abstract class with abstract methods instantiated

+E: 54:main: Abstract class with abstract methods instantiated

+E: 55:main: Abstract class with abstract methods instantiated
\ No newline at end of file