Add pylint to depot_tools.

third_party/logilab/common/interface.py

+# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This file is part of logilab-common.
+#
+# logilab-common is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 2.1 of the License, or (at your option) any
+# later version.
+#
+# logilab-common 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 Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License along
+# with logilab-common.  If not, see <http://www.gnu.org/licenses/>.
+"""Bases class for interfaces to provide 'light' interface handling.
+
+ TODO:
+  _ implements a check method which check that an object implements the
+    interface
+  _ Attribute objects
+
+  This module requires at least python 2.2
+"""
+__docformat__ = "restructuredtext en"
+
+
+class Interface(object):
+    """Base class for interfaces."""
+    def is_implemented_by(cls, instance):
+        return implements(instance, cls)
+    is_implemented_by = classmethod(is_implemented_by)
+
+
+def implements(obj, interface):
+    """Return true if the give object (maybe an instance or class) implements
+    the interface.
+    """
+    kimplements = getattr(obj, '__implements__', ())
+    if not isinstance(kimplements, (list, tuple)):
+        kimplements = (kimplements,)
+    for implementedinterface in kimplements:
+        if issubclass(implementedinterface, interface):
+            return True
+    return False
+
+
+def extend(klass, interface, _recurs=False):
+    """Add interface to klass'__implements__ if not already implemented in.
+
+    If klass is subclassed, ensure subclasses __implements__ it as well.
+
+    NOTE: klass should be e new class.
+    """
+    if not implements(klass, interface):
+        try:
+            kimplements = klass.__implements__
+            kimplementsklass = type(kimplements)
+            kimplements = list(kimplements)
+        except AttributeError:
+            kimplementsklass = tuple
+            kimplements = []
+        kimplements.append(interface)
+        klass.__implements__ = kimplementsklass(kimplements)
+        for subklass in klass.__subclasses__():
+            extend(subklass, interface, _recurs=True)
+    elif _recurs:
+        for subklass in klass.__subclasses__():
+            extend(subklass, interface, _recurs=True)