Merge lp:~allenap/lazr.delegates/multiple-interfaces into lp:~launchpad-pqm/lazr.delegates/devel

[Gavin Panella]

[Gavin Panella (allenap)]

This branch allows delegates() to accept multiple interfaces. I think
the tests explain it quite well, so I won't repeat all of that here.

I also changed the use of hasattr() to getattr() to prevent swallowing
errors.

[Gary Poster (gary)]

I thought I had reviewed this a long time ago! Sorry that this got lost in the cracks. It looks good to me.

review: Approve

[Gavin Panella (allenap)]

> I thought I had reviewed this a long time ago! Sorry that this got lost in
> the cracks. It looks good to me.

Woohoo, thanks Gary!

=== modified file 'src/lazr/delegates/README.txt'
--- src/lazr/delegates/README.txt	2009-03-24 19:51:29 +0000
+++ src/lazr/delegates/README.txt	2009-04-14 16:07:52 +0000
@@ -25,11 +25,12 @@
 Usage
 =====
 
-The ``delegates`` function makes a class implement an interface by
-delegating the implementation to another object. In the case of a class
-providing an adapter, that object will be the 'context', but it can
-really be any object stored in an attribute. So while the interfaces use
-an inheritance mechanism, the classes use a composition mechanism.
+The ``delegates`` function makes a class implement zero or more
+interfaces by delegating the implementation to another object. In the
+case of a class providing an adapter, that object will be the 'context',
+but it can really be any object stored in an attribute. So while the
+interfaces use an inheritance mechanism, the classes use a composition
+mechanism.
 
 For example we can define two interfaces IFoo0 <- IFoo...
 
@@ -126,6 +127,66 @@
     ...
     TypeError: delegates() can be used only from a class definition.
 
+Multiple interfaces can be specified by passing an iterable to
+delegates().
+
+    >>> class IOther(Interface):
+    ...     another = Attribute("another attribute")
+
+    >>> class BaseOtherFoo(BaseFoo):
+    ...     another = 'yes, another'
+
+    >>> class SomeOtherClass(object):
+    ...     delegates([IFoo, IOther])
+
+    >>> s = SomeOtherClass()
+    >>> s.context = BaseOtherFoo()
+    >>> s.another
+    'yes, another'
+
+    >>> s.baz
+    'hi baz!'
+
+    >>> s.spoo
+    'some spoo'
+
+    >>> IFoo.providedBy(s)
+    True
+
+    >>> IOther.providedBy(s)
+    True
+
+This can be convenient when decorating an existing object.
+
+    >>> from zope.interface import implements
+    >>> class MoreFoo(BaseFoo, BaseOtherFoo):
+    ...     implements(IFoo, IOther)
+
+    >>> foo = MoreFoo()
+
+    >>> from zope.interface import providedBy
+    >>> class WithExtraTeapot(object):
+    ...     delegates(providedBy(foo))
+    ...     teapot = 'i am a teapot'
+
+    >>> foo_with_teapot = WithExtraTeapot()
+    >>> foo_with_teapot.context = foo
+
+    >>> foo_with_teapot.baz
+    'hi baz!'
+
+    >>> foo_with_teapot.another
+    'yes, another'
+
+    >>> foo_with_teapot.teapot
+    'i am a teapot'
+
+    >>> IFoo.providedBy(foo_with_teapot)
+    True
+
+    >>> IOther.providedBy(foo_with_teapot)
+    True
+
 ==============
 Implementation
 ==============

=== modified file 'src/lazr/delegates/_delegates.py'
--- src/lazr/delegates/_delegates.py	2009-03-24 19:51:29 +0000
+++ src/lazr/delegates/_delegates.py	2009-04-14 16:07:52 +0000
@@ -28,9 +28,10 @@
 
 from zope.interface.advice import addClassAdvisor
 from zope.interface import classImplements
-
-
-def delegates(interface, context='context'):
+from zope.interface.interfaces import IInterface
+
+
+def delegates(interface_spec, context='context'):
     """Make an adapter into a decorator.
 
     Use like:
@@ -78,7 +79,7 @@
         raise TypeError(
             "delegates() can be used only from a class definition.")
 
-    locals['__delegates_advice_data__'] = interface, context
+    locals['__delegates_advice_data__'] = interface_spec, context
     addClassAdvisor(_delegates_advice, depth=2)
 
 
@@ -88,15 +89,21 @@
     This function connects the decorator class to the delegate class.
     Only new-style classes are supported.
     """
-    interface, contextvar = cls.__dict__['__delegates_advice_data__']
+    interface_spec, contextvar = cls.__dict__['__delegates_advice_data__']
     del cls.__delegates_advice_data__
     if type(cls) is ClassType:
         raise TypeError(
             'Cannot use delegates() on a classic class: %s.' % cls)
-    classImplements(cls, interface)
-    for name in interface:
-        if not hasattr(cls, name):
-            setattr(cls, name, Passthrough(name, contextvar))
+    if IInterface.providedBy(interface_spec):
+        interfaces = [interface_spec]
+    else:
+        interfaces = interface_spec
+    not_found = object()
+    for interface in interfaces:
+        classImplements(cls, interface)
+        for name in interface:
+            if getattr(cls, name, not_found) is not_found:
+                setattr(cls, name, Passthrough(name, contextvar))
     return cls