Add singleton support to LazyItemsDict to make it easier to use with arbitrary function calls.

svn path=/main/trunk/; revision=3149

2 files changed, 25 insertions, 28 deletions

diff --git a/pym/portage.py b/pym/portage.py
index f53436ba0..7a8258547 100644
--- a/pym/portage.py
+++ b/pym/portage.py
@@ -1404,18 +1404,9 @@ class config:
 				# XXX Global usage of db... Needs to go away somehow.
 				global db, root
 				if "auto" in self["USE_ORDER"].split(":") and db.has_key(root) and db[root].has_key("vartree"):
-					class LazyAutouse(object):
-						def __init__(self, *pargs, **kwargs):
-							self._use = None
-							self._pargs = pargs
-							self._kwargs = kwargs
-						def __call__(self):
-							if self._use is None:
-								global db, root
-								self._use = autouse(db[root]["vartree"], *self._pargs, **self._kwargs)
-							return self._use
 					self.configdict["auto"] = portage_util.LazyItemsDict(self.configdict["auto"])
-					self.configdict["auto"].addLazyItem("USE", LazyAutouse(use_cache=use_cache))
+					self.configdict["auto"].addLazySingleton("USE", autouse,
+						db[root]["vartree"], use_cache=use_cache)
 				else:
 					self.configdict["auto"]["USE"]=""
 			else:
@@ -6478,23 +6469,13 @@ def getvirtuals(myroot):
 	return settings.getvirtuals(myroot)
 
 def do_vartree(mysettings):
-	class LazyVirtualsItem(object):
-		def __init__(self, myroot):
-			self._myroot = myroot
-			self._virtuals = None
-		def __call__(self):
-			if self._virtuals is None:
-				global settings
-				self._virtuals = settings.getvirtuals(self._myroot)
-			return self._virtuals
-
-	global db, root
+	global db, root, settings
 	db["/"] = portage_util.LazyItemsDict()
-	db["/"].addLazyItem("virtuals", LazyVirtualsItem("/"))
+	db["/"].addLazySingleton("virtuals", settings.getvirtuals, "/")
 	db["/"]["vartree"] = vartree("/")
 	if root!="/":
 		db[root] = portage_util.LazyItemsDict()
-		db[root].addLazyItem("virtuals", LazyVirtualsItem(root))
+		db[root].addLazySingleton("virtuals", settings.getvirtuals, root)
 		db[root]["vartree"] = vartree(root)
 	#We need to create the vartree first, then load our settings, and then set up our other trees
 
diff --git a/pym/portage_util.py b/pym/portage_util.py
index cd69733ba..a1e2d0227 100644
--- a/pym/portage_util.py
+++ b/pym/portage_util.py
@@ -722,15 +722,31 @@ class LazyItemsDict(dict):
 			self.update(initial_items)
 			if isinstance(initial_items, LazyItemsDict):
 				self.lazy_items.update(initial_items.lazy_items)
-	def addLazyItem(self, item_key, value_callable):
+	def addLazyItem(self, item_key, value_callable, *pargs, **kwargs):
 		"""Add a lazy item for the given key.  When the item is requested,
-		value_callable will be called with no arguments."""
-		self.lazy_items[item_key] = value_callable
+		value_callable will be called with *pargs and **kwargs arguments."""
+		self.lazy_items[item_key] = (value_callable, pargs, kwargs)
 		# make it show up in self.keys(), etc...
 		dict.__setitem__(self, item_key, None)
+	def addLazySingleton(self, item_key, value_callable, *pargs, **kwargs):
+		"""This is like addLazyItem except value_callable will only be called
+		a maximum of 1 time and the result will be cached for future requests."""
+		class SingletonItem(object):
+			def __init__(self, value_callable, *pargs, **kwargs):
+				self._callable = value_callable
+				self._pargs = pargs
+				self._kwargs = kwargs
+				self._called = False
+			def __call__(self):
+				if not self._called:
+					self._called = True
+					self._value = self._callable(*self._pargs, **self._kwargs)
+				return self._value
+		self.addLazyItem(item_key, SingletonItem(value_callable, *pargs, **kwargs))
 	def __getitem__(self, item_key):
 		if item_key in self.lazy_items:
-			return self.lazy_items[item_key]()
+			value_callable, pargs, kwargs = self.lazy_items[item_key]
+			return value_callable(*pargs, **kwargs)
 		else:
 			return dict.__getitem__(self, item_key)
 	def __setitem__(self, item_key, value):