def subscribe(self, person, subscribed_by=None, essential=False):
"""See ISpecification."""
if subscribed_by is None:
subscribed_by = person
# Create or modify a user's subscription to this blueprint.
# First see if a relevant subscription exists, and if so, return it
sub = self.subscription(person)
if sub is not None:
if sub.essential != essential:
# If a subscription already exists, but the value for
# 'essential' changes, there's no need to create a new
# subscription, but we modify the existing subscription
# and notify the user about the change.
sub.essential = essential
# The second argument should really be a copy of sub with
# only the essential attribute changed, but we know
# that we can get away with not examining the attribute
# at all - it's a boolean!
notify(
ObjectModifiedEvent(sub,
sub, ['essential'],
user=subscribed_by))
return sub
# since no previous subscription existed, create and return a new one
sub = SpecificationSubscription(specification=self,
person=person,
essential=essential)
property_cache = get_property_cache(self)
if 'subscription' in property_cache:
from lp.registry.model.person import person_sort_key
property_cache.subscriptions.append(sub)
property_cache.subscriptions.sort(
key=lambda sub: person_sort_key(sub.person))
if self.information_type in PRIVATE_INFORMATION_TYPES:
# Grant the subscriber access if they can't see the
# specification.
service = getUtility(IService, 'sharing')
ignored, ignored, shared_specs = service.getVisibleArtifacts(
person, specifications=[self], ignore_permissions=True)
if not shared_specs:
service.ensureAccessGrants([person],
subscribed_by,
specifications=[self])
notify(ObjectCreatedEvent(sub, user=subscribed_by))
return sub
