15: Added ipalib.base2 module where I'm experimenting with a 3rd approach that is a hybrid of the first two: a decoupled late binding OO strategy

ipalib/base2.py

@@ -0,0 +1,102 @@
+# Authors:
+#   Jason Gerard DeRose <jderose@redhat.com>
+#
+# Copyright (C) 2008  Red Hat
+# see file 'COPYING' for use and warranty information
+#
+# 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; version 2 only
+#
+# 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
+
+"""
+Base classes for plug-in architecture and generative API.
+"""
+
+import inspect
+import exceptions
+from base import NameSpace
+
+
+class Named(object):
+	def __get_name(self):
+		return self.__class__.__name__
+	name = property(__get_name)
+
+
+class WithObj(Named):
+	_obj = None
+	__obj = None
+
+	def __get_obj(self):
+		return self.__obj
+	def __set_obj(self, obj):
+		if self.__obj is not None:
+			raise exceptions.TwiceSetError(self.__class__.__name__, 'obj')
+		assert isinstance(obj, Named)
+		assert isinstance(self._obj, str)
+		assert obj.name == self._obj
+		self.__obj = obj
+		assert self.obj is obj
+	obj = property(__get_obj, __set_obj)
+
+
+class Command(WithObj):
+	pass
+
+class Property(WithObj):
+	pass
+
+class Object(Named):
+	pass
+
+
+class Registrar(object):
+	__object = None
+	__commands = None
+	__properties = None
+
+	def __init__(self):
+		self.__tmp_objects = {}
+		self.__tmp_commands = {}
+		self.__tmp_properties = {}
+
+	def __get_objects(self):
+		return self.__objects
+	objects = property(__get_objects)
+
+	def __get_commands(self):
+		return self.__commands
+	commands = property(__get_commands)
+
+	def __get_target(self, i):
+		if isinstance(i, Object):
+			return (self.__tmp_objects, i.name)
+		if isinstance(i, Command):
+			return (self.__tmp_commands, i.name)
+		assert isinstance(i, Property)
+
+
+	def register(self, cls):
+		assert inspect.isclass(cls)
+		assert issubclass(cls, Named)
+		i = cls()
+		(target, key) = self.__get_target(i)
+		target[key] = i
+
+	def finalize(self):
+		for cmd in self.__tmp_commands.values():
+			if cmd._obj is None:
+				continue
+			obj = self.__tmp_objects[cmd._obj]
+			cmd.obj = obj
+		self.__objects = NameSpace(self.__tmp_objects)
+		self.__commands = NameSpace(self.__tmp_commands)

ipalib/exceptions.py

@@ -63,3 +63,7 @@ class RegistrationError(IPAError):
 
 class PrefixError(IPAError):
 	msg = 'class name %r must start with %r'
+
+
+class TwiceSetError(IPAError):
+	msg = '%s.%s cannot be set twice'

ipalib/tests/test_base2.py

@@ -0,0 +1,142 @@
+# Authors:
+#   Jason Gerard DeRose <jderose@redhat.com>
+#
+# Copyright (C) 2008  Red Hat
+# see file 'COPYING' for use and warranty information
+#
+# 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; version 2 only
+#
+# 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
+
+"""
+Unit tests for `ipalib.base` module.
+"""
+
+from ipalib import base2 as base
+from ipalib import exceptions
+
+
+def read_only(obj, name):
+	"""
+	Check that a given property is read-only.
+	Returns the value of the property.
+	"""
+	assert isinstance(obj, object)
+	assert hasattr(obj, name)
+	raised = False
+	try:
+		setattr(obj, name, 'some new obj')
+	except AttributeError:
+		raised = True
+	assert raised
+	return getattr(obj, name)
+
+
+class ClassChecker(object):
+	cls = None # Override this is subclasses
+
+	def new(self, *args, **kw):
+		return self.cls(*args, **kw)
+
+	def args(self):
+		return []
+
+	def kw(self):
+		return {}
+
+	def std(self):
+		return self.new(*self.args(), **self.kw())
+
+
+
+def test_Named():
+	class named_class(base.Named):
+		pass
+
+	i = named_class()
+	assert i.name == 'named_class'
+
+
+def test_WithObj():
+	class some_object(base.Named):
+		pass
+
+	class another_object(base.Named):
+		pass
+
+	class some_command(base.WithObj):
+		_obj = 'some_object'
+
+	obj = some_object()
+	cmd = some_command()
+
+	# Test that it can be set:
+	assert cmd.obj is None
+	cmd.obj = obj
+	assert cmd.obj is obj
+
+	# Test that it cannot be set twice:
+	raised = False
+	try:
+		cmd.obj = obj
+	except exceptions.TwiceSetError:
+		raised = True
+	assert raised
+
+	# Test that it can't be set with the wrong name:
+	obj = another_object()
+	cmd = some_command()
+	raised = False
+	try:
+		cmd.obj = obj
+	except AssertionError:
+		raised = True
+	assert raised
+
+
+def test_Registar():
+	class adduser(base.Command):
+		_obj = 'user'
+	class moduser(base.Command):
+		_obj = 'user'
+	class deluser(base.Command):
+		_obj = 'user'
+	class finduser(base.Command):
+		_obj = 'user'
+	class kinit(base.Command):
+		pass
+	class user(base.Object):
+		pass
+	class group(base.Object):
+		pass
+
+	r = base.Registrar()
+	r.register(adduser)
+	r.register(moduser)
+	r.register(deluser)
+	r.register(finduser)
+	r.register(kinit)
+	r.register(user)
+	r.register(group)
+
+	r.finalize()
+	assert len(r.commands) == 5
+	assert len(r.objects) == 2
+
+	obj = r.objects.user
+	assert type(obj) is user
+	for name in ['adduser', 'moduser', 'deluser', 'finduser']:
+		cmd = r.commands[name]
+		assert type(cmd) is locals()[name]
+		assert cmd.obj is obj
+
+	assert r.commands.kinit.obj is None