44: Added Plugin.finalize() method called by API after all plugin instances are created; updated corresponding unit tests

ipalib/plugable.py

@@ -49,16 +49,27 @@ class Plugin(object):
 	Base class for all plugins.
 	"""
 
-	def __init__(self, api):
-		self.__api = api
+	__api = None
 
 	def __get_api(self):
 		"""
-		Returns the plugable.API object this plugin has been instatiated in.
+		Returns the plugable.API instance passed to Plugin.finalize(), or
+		or returns None if finalize() has not yet been called.
 		"""
 		return self.__api
 	api = property(__get_api)
 
+	def finalize(self, api):
+		"""
+		After all the plugins are instantiated, the plugable.API calls this
+		method, passing itself as the only argument. This is where plugins
+		should check that other plugins they depend upon have actually be
+		loaded.
+		"""
+		assert self.__api is None, 'finalize() can only be called once'
+		assert api is not None, 'finalize() argument cannot be None'
+		self.__api = api
+
 	def __get_name(self):
 		"""
 		Returns the class name of this instance.
@@ -280,14 +291,18 @@ class Registrar(object):
 
 class API(ReadOnly):
 	def __init__(self, registrar):
+		object.__setattr__(self, '_API__plugins', [])
 		for (base, plugins) in registrar:
 			ns = NameSpace(self.__plugin_iter(base, plugins))
 			assert not hasattr(self, base.__name__)
 			object.__setattr__(self, base.__name__, ns)
+		for plugin in self.__plugins:
+			plugin.finalize(self)
+			assert plugin.api is self
 
 	def __plugin_iter(self, base, plugins):
 		assert issubclass(base.proxy, Proxy)
 		for cls in plugins:
-			plugin = cls(self)
-			assert plugin.api is self
+			plugin = cls()
+			self.__plugins.append(plugin)
 			yield base.proxy(plugin)

ipalib/tests/test_plugable.py

@@ -43,17 +43,25 @@ def test_from_cli():
 
 def test_Plugin():
 	api = 'the api instance'
-	p = plugable.Plugin(api)
-	assert read_only(p, 'api') is api
+	p = plugable.Plugin()
 	assert read_only(p, 'name') == 'Plugin'
 	assert repr(p) == '%s.Plugin()' % plugable.__name__
+	assert read_only(p, 'api') is None
+	raises(AssertionError, p.finalize, None)
+	p.finalize(api)
+	assert read_only(p, 'api') is api
+	raises(AssertionError, p.finalize, api)
 
 	class some_plugin(plugable.Plugin):
 		pass
-	p = some_plugin(api)
-	assert read_only(p, 'api') is api
+	p = some_plugin()
 	assert read_only(p, 'name') == 'some_plugin'
 	assert repr(p) == '%s.some_plugin()' % __name__
+	assert read_only(p, 'api') is None
+	raises(AssertionError, p.finalize, None)
+	p.finalize(api)
+	assert read_only(p, 'api') is api
+	raises(AssertionError, p.finalize, api)
 
 
 def test_ReadOnly():