Add jaraco.classes-3.2.1

lib/jaraco/classes/meta.py

@@ -0,0 +1,66 @@
+"""
+meta.py
+
+Some useful metaclasses.
+"""
+
+
+class LeafClassesMeta(type):
+    """
+    A metaclass for classes that keeps track of all of them that
+    aren't base classes.
+
+    >>> Parent = LeafClassesMeta('MyParentClass', (), {})
+    >>> Parent in Parent._leaf_classes
+    True
+    >>> Child = LeafClassesMeta('MyChildClass', (Parent,), {})
+    >>> Child in Parent._leaf_classes
+    True
+    >>> Parent in Parent._leaf_classes
+    False
+
+    >>> Other = LeafClassesMeta('OtherClass', (), {})
+    >>> Parent in Other._leaf_classes
+    False
+    >>> len(Other._leaf_classes)
+    1
+    """
+
+    def __init__(cls, name, bases, attrs):
+        if not hasattr(cls, '_leaf_classes'):
+            cls._leaf_classes = set()
+        leaf_classes = getattr(cls, '_leaf_classes')
+        leaf_classes.add(cls)
+        # remove any base classes
+        leaf_classes -= set(bases)
+
+
+class TagRegistered(type):
+    """
+    As classes of this metaclass are created, they keep a registry in the
+    base class of all classes by a class attribute, indicated by attr_name.
+
+    >>> FooObject = TagRegistered('FooObject', (), dict(tag='foo'))
+    >>> FooObject._registry['foo'] is FooObject
+    True
+    >>> BarObject = TagRegistered('Barobject', (FooObject,), dict(tag='bar'))
+    >>> FooObject._registry is BarObject._registry
+    True
+    >>> len(FooObject._registry)
+    2
+
+    '...' below should be 'jaraco.classes' but for pytest-dev/pytest#3396
+    >>> FooObject._registry['bar']
+    <class '....meta.Barobject'>
+    """
+
+    attr_name = 'tag'
+
+    def __init__(cls, name, bases, namespace):
+        super(TagRegistered, cls).__init__(name, bases, namespace)
+        if not hasattr(cls, '_registry'):
+            cls._registry = {}
+        meta = cls.__class__
+        attr = getattr(cls, meta.attr_name, None)
+        if attr:
+            cls._registry[attr] = cls