Return empty array for delegation with nil manager

If a NetworkManager doesn't have a parent_manager (e.g. Nuage) return an empty array instead of a nil

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1767747

app/models/manageiq/providers/network_manager.rb

@@ -28,59 +28,40 @@ class << model_name
     has_many :load_balancer_health_checks,        :foreign_key => :ems_id, :dependent => :destroy
     has_many :load_balancer_health_check_members, :through => :load_balancer_health_checks
 
-    # Uses "ext_management_systems"."parent_ems_id" instead of "ext_management_systems"."id"
-    #
-    # ORDER BY ((
-    #   SELECT COUNT(*)
-    #   FROM "vms"
-    #   WHERE "ext_management_systems"."parent_ems_id" = "vms"."ems_id"
-    # ))
-    #
-    # So unlike the parent class definition, this looks at "ext_management_systems"."parent_ems_id" instead of
-    # "ext_management_systems"."id"
-    # If we are able to define a has_many :vms, :through => :parent_manager, that does actual join, this code should
-    # not be needed.
-    virtual_total :total_vms, :vms, {
-      :arel => lambda do |t|
-        foreign_table = Vm.arel_table
-        local_key     = :parent_ems_id
-        foreign_key   = :ems_id
-        arel_column   = Arel.star.count
-        t.grouping(foreign_table.project(arel_column).where(t[local_key].eq(foreign_table[foreign_key])))
-      end
-    }
-
     alias all_cloud_networks cloud_networks
 
     belongs_to :parent_manager,
                :foreign_key => :parent_ems_id,
                :class_name  => "ManageIQ::Providers::BaseManager",
                :autosave    => true
 
-    has_many :availability_zones, -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :availability_zones,            -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :flavors,                       -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :cloud_tenants,                 -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :cloud_resource_quotas,         -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :cloud_volumes,                 -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :cloud_volume_snapshots,        -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :cloud_object_store_containers, -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :cloud_object_store_objects,    -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :key_pairs,                     -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id, :class_name  => "AuthKeyPair", :as => :resource
+    has_many :hosts,                         -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :vms,                           -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :miq_templates,                 -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+    has_many :vms_and_templates,             -> { where.not(:ems_id => nil) }, :primary_key => :parent_ems_id, :foreign_key => :ems_id
+
+    virtual_total :total_vms, :vms
+    virtual_total :total_miq_templates, :miq_templates
+    virtual_total :total_vms_and_templates, :vms_and_templates
 
     # Relationships delegated to parent manager
-    delegate :cloud_tenants,
-             :flavors,
-             :cloud_resource_quotas,
-             :cloud_volumes,
-             :cloud_volume_snapshots,
-             :cloud_object_store_containers,
-             :cloud_object_store_objects,
-             :key_pairs,
+    virtual_delegate
              :orchestration_stacks,
              :orchestration_stacks_resources,
              :direct_orchestration_stacks,
              :resource_groups,
-             :vms,
-             :total_vms,
-             :vms_and_templates,
-             :total_vms_and_templates,
-             :miq_templates,
-             :total_miq_templates,
-             :hosts,
              :to        => :parent_manager,
-             :allow_nil => true
+             :allow_nil => true,
+             :default => []
 
     def self.supported_types_and_descriptions_hash
       supported_subclasses.select(&:supports_ems_network_new?).each_with_object({}) do |klass, hash|

spec/models/manageiq/providers/network_manager_spec.rb

@@ -8,9 +8,23 @@
     expect(ems.id).not_to eq(ems.network_manager.id)
     expect(ems.vms).to match_array([vms])
     expect(ems.network_manager.vms).to match_array([vms])
+    expect(ems.total_vms).to eq(1)
     expect(ems.miq_templates).to match_array([template])
     expect(ems.network_manager.miq_templates).to match_array([template])
+    expect(ems.total_miq_templates).to eq(1)
     expect(ems.vms_and_templates).to match_array([vms, template])
     expect(ems.network_manager.vms_and_templates).to match_array([vms, template])
+    expect(ems.total_vms_and_templates).to eq(2)
+  end
+
+  it "delegates vms and templates to parent manager (when no manager)" do
+    ems = FactoryBot.create(:ems_openstack_network, :parent => nil)
+
+    expect(ems.vms).to eq([])
+    expect(ems.total_vms).to eq(0)
+    expect(ems.miq_templates).to eq([])
+    expect(ems.total_miq_templates).to eq(0)
+    expect(ems.vms_and_templates).to eq([])
+    expect(ems.total_vms_and_templates).to eq(0)
   end
 end