Proper parent initialization

[Ladas]

Set :parent to manager only if not sent in options and explicitly pass :parent => nil, because it has a priority over :arel in the DB strategies.

So e.g. for AWS, when we use a DB strategy, it's enough to use parent and association, since the related Vm can only be in the scope of manager.vms. But for Ansible, the crosslink can be to any VM, therefore we use a generic arel to get to the right Vm.

The priority for DB strategy starting with higher priority is: :custom_db_finder, :parent & :association, :arel. So the first defined is used for fetching data from the DB.

[Ladas]

@miq-bot assign @agrare

[miq-bot]

Checked commits Ladas/manageiq@ff28bce~...9265a8b with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
2 files checked, 0 offenses detected
Everything looks good. 🍰

[durandom]

could you try to update the description to be more explanatory?
I guess I need this when it comes to documentation
e.g. is there a case where you want to pass a parent although strategy is :db ?
and what do you mean by

has a priority over :arel in the DB strategies.

[durandom]

The priorities are here

manageiq/app/models/manager_refresh/inventory_collection.rb

Lines 426 to 441 in 6d90d8d

	def db_relation(selection = nil, projection = nil)
	relation = if !custom_db_finder.blank?
	custom_db_finder.call(self, selection, projection)
	else
	rel = if !parent.nil? && !association.nil?
	parent.send(association)
	elsif !arel.nil?
	arel
	end
	rel = rel.where(selection) if rel && selection
	rel = rel.select(projection) if rel && projection
	rel
	end
	relation || []
	end

[durandom]

ok. I think what confuses / annoys me, is that we have to pass something as nil
Maybe defaulting the :parent to manager is not so good...

👍 until we see a lot of :parent => nil

[agrare]

Are there any specs around cross-linking? Seems this should have caused a test failure with good test coverage

[durandom]

@agrare this is just the DSL and only ansible tower is using it. And the DSL is only syntactic sugar.

Though I agree we should move the spec to use the DSL soon.

re-assigning to @kbrock as he merged the original PR

[durandom]

@miq-bot assign @kbrock

[kbrock]

looks to handle the use case well. thanks ladas