libstore: forbid addWantedGoals when finished

due to event loop scheduling behavior it's possible for a derivation
goal to fully finish (having seen all paths it was asked to create),
but to not notify the worker of this in time to prevent another goal
asking the recently-finished goal for more outputs. if this happened
the finished goal would ignore the request for more outputs since it
considered itself fully done, and the delayed result reporting would
cause the requesting goal to assume its request had been honored. if
the requested goal had finished *properly* the worker would recreate
it instead of asking for more outputs, and this would succeed. it is
thus safe to always recreate goals once they are done, so we now do.

Change-Id: Ifedd69ca153372c623abe9a9b49cd1523588814f

0 files changed, 0 insertions, 0 deletions