Local component look-up
=======================

``IComponentLookup`` adapter
-----------------------------

In order to do context-based component look-up, the Component
Architecture adapts the context to ``IComponentLookup``.  zope.site's
default adapter uses the ``ILocation`` API to walk up the object tree
and find a site that way.  Five provides its own adapter that also
supports acquisitional parents.

First, we register Five's adapter:

  >>> import zope.component
  >>> from Products.Five.component import siteManagerAdapter
  >>> zope.component.provideAdapter(siteManagerAdapter)

Now we create a site object with a stub component registry:

  >>> from OFS.ObjectManager import ObjectManager
  >>> from zope.interface import alsoProvides
  >>> from zope.location.interfaces import ISite

  >>> components = object()
  >>> site = ObjectManager()
  >>> site.setSiteManager(components)
  >>> alsoProvides(site, ISite)

When we adapt the site itself, we obviously get its component
registry:

  >>> from zope.component.interfaces import IComponentLookup
  >>> IComponentLookup(site) is components
  True
 
In case the adapted object has an acquisition context, acquisition
is used to retrieve the closest site:
  
  >>> ob = ObjectManager()
  >>> ob2 = ObjectManager()
  >>> ob = ob.__of__(site)
  >>> ob2 = ob2.__of__(ob)
  >>> IComponentLookup(ob2) is components
  True

The adapter also works using the ``ILocation`` API by inspecting the
``__parent__`` object instead of using the acquisition parent:

  >>> from zope.location import Location
  >>> ob = Location()
  >>> ob2 = Location()
  >>> ob.__parent__ = site
  >>> ob2.__parent__ = ob
  >>> IComponentLookup(ob2) is components
  True

If it is unable to find a site and therefore a component registry, the
global component registry is returned:

  >>> from zope.component import getGlobalSiteManager
  >>> orphan = ObjectManager()
  >>> IComponentLookup(orphan) is getGlobalSiteManager()
  True


Clean up:
---------

  >>> from zope.component.testing import tearDown
  >>> tearDown()