See #9869 and #9929.
The problem arises from the following example:
class Project < ActiveRecord::Base
scope :completed, -> { where completed: true }
end
class MajorProject < Project
end
When calling:
MajorProject.where(tasks_count: 10).completed
This expands to:
MajorProject.where(tasks_count: 10).scoping {
MajorProject.completed
}
However the lambda for the `completed` scope is defined on Project. This
means that when it is called, `self` is Project rather than
MajorProject. So it expands to:
MajorProject.where(tasks_count: 10).scoping {
Project.where(completed: true)
}
Since the scoping was applied on MajorProject, and not Project, this
fails to apply the tasks_count condition.
The solution is to make scoping apply across STI classes. I am slightly
concerned about the possible side-effects of this, but no tests fail and
it seems ok. I guess we'll see.
