Upgrading Plone extensions using GenericSetup upgrade steps. A great idea. Easy to develop, easy to use and document. A unified upgrade interface for every Plone extension.
Anyway, there's actually an annoying issue on upgrade steps: upgrade steps for component "foo" are exposed in sites where the "foo" component is not installed.
Wow, managers on instances where various different Plone sites are installed have to be careful on this. Running an upgrade step of a component that is not installed in a site may be harmful. Even if upgrade scripts are supposed to be defensively programmed.
Having several Plone extensions, I made a decorator based generic safety belt. Of course this does not prevent GS showing the upgrade steps but executing such upgrade steps raises an explicit error message and does not execute the upgrade step.
Just add these lines to your utils.py:
from zope.component import getUtility from Products.CMFCore.interfaces import ISiteRoot from config import PROJECTNAME class NotInstalledComponent(LookupError): def __init__(self, cpt_name): self.cpt_name = cpt_name return def __str__(self): msg = ("Component '%s' is not installed in this site." " You can't run its upgrade steps." % self.cpt_name) return msg class IfInstalled(object): """The decorator""" def __init__(self, prod_name=PROJECTNAME): """@param prod_name: as shown in quick installer""" self.prod_name = prod_name def __call__(self, func): """@param func: the decorated function""" def wrapper(setuptool): portal = getUtility(ISiteRoot) qi = portal.portal_quickinstaller installed_ids = [p['id'] for p in qi.listInstalledProducts()] if self.prod_name not in installed_ids: raise NotInstalledComponent(self.prod_name) return func(setuptool) wrapper.__name__ = func.__name__ wrapper.__dict__.update(func.__dict__) wrapper.__doc__ = func.__doc__ wrapper.__module__ = func.__module__ return wrapper
Then your upgrade scripts should be decorated like this in your upgrades.py.
from utils import IfInstalled @IfInstalled() def someUpgradeFunction(setuptool): # Stuff as usual...