#3045: [RFC] Ordered ExtensionPoint implementation
-------------------------+--------------------------------------------------
Reporter: athomas | Owner: jonas
Type: enhancement | Status: new
Priority: low | Milestone:
Component: general | Version: devel
Severity: trivial | Keywords:
-------------------------+--------------------------------------------------
In the same vein as `SingletonExtensionPoint`, this uses a config entry to
determine the order in which the extensions are returned:
{{{
#!python
class ExtensionPoint(property):
""" An extension point, possibly ordered by a configuration option.
Entries
missing from the option can be excluded. """
def __init__(self, interface, cfg_section=None, cfg_property=None,
exclude_missing=False):
property.__init__(self, self.extensions)
self.interface = interface
self.__doc__ = 'List of components that implement `%s`' % \
self.interface.__name__
self.cfg_section = cfg_section or 'interfaces'
self.cfg_property = cfg_property or interface.__name__.lower()
self.exclude_missing = exclude_missing
def extensions(self, component):
"""Return a list of components that declare to implement the
extension point interface."""
order = filter(None, component.config.getlist(self.cfg_section,
self.cfg_property))
extensions = ComponentMeta._registry.get(self.interface, [])
extensions = filter(None, [component.compmgr[cls] for cls in
extensions
if not self.exclude_missing
or not order
or cls.__name__ in order])
if order:
def compare(x, y):
x, y = x.__class__.__name__, y.__class__.__name__
if x not in order:
return int(y in order)
if y not in order:
return -int(x in order)
return cmp(order.index(x), order.index(y))
extensions.sort(compare)
return extensions
def __repr__(self):
"""Return a textual representation of the extension point."""
return '<ExtensionPoint %s>' % self.interface.__name__
}}}
This could replace the existing !ExtensionPoint class and add ordering
automatically to all existing interfaces. Ordering for any interface can
be specified in the `[interfaces]` section. eg.
{{{
[interfaces]
iconfigurable = TicketSystem, WikiSystem
ipermissionrequestor = PermissionSystem
}}}
--
Ticket URL: <http://projects.edgewall.com/trac/ticket/3045>
The Trac Project <http://trac.edgewall.com/>
_______________________________________________
Trac-Tickets mailing list
[email protected]
http://lists.edgewall.com/mailman/listinfo/trac-tickets
