Fixes #37043 - Inheritance overrides host facets

app/models/concerns/facets/base.rb

@@ -40,11 +40,11 @@ module ClassMethods
       # Change attributes that will be sent to an facet based on inherited values from the hostgroup.
       def inherited_attributes(hostgroup, facet_attributes)
         _, facet_config = Facets.find_facet_by_class(self, :host)
+        return facet_attributes unless facet_config.has_hostgroup_configuration? && hostgroup
 
-        if facet_config.has_hostgroup_configuration? && hostgroup
-          facet_attributes = hostgroup.inherited_facet_attributes(facet_config)
+        hostgroup.inherited_facet_attributes(facet_config).merge(facet_attributes || {}) do |key, left, right|
+          facet_attributes.include?(key) ? right : left
         end
-        facet_attributes
       end
 
       # Use this method to populate host's fields based on fact values exposed by the importer.

test/unit/facet_test.rb

@@ -298,5 +298,41 @@ def my_attribute=(val)
 
       assert_equal({'to_inherit' => 'val1'}, actual['hostgroup_facet_attributes'])
     end
+
+    test 'hostgroup facet does not override attributes from host' do
+      Facets.register :hostgroup_facet do
+        configure_host TestFacet
+        configure_hostgroup TestHostgroupFacet
+      end
+
+      host = Host::Managed.new
+      hostgroup = FactoryBot.create(:hostgroup, :hostgroup_facet => TestHostgroupFacet.new)
+
+      TestHostgroupFacet.stubs(:attributes_to_inherit).returns([])
+      TestHostgroupFacet.inherit_attributes :to_inherit
+      TestHostgroupFacet.any_instance.stubs(:attributes).returns({:to_inherit => 'val1'})
+
+      actual = host.apply_inherited_attributes('hostgroup' => hostgroup, 'hostgroup_facet_attributes' => { 'to_inherit' => 'val3' })
+
+      assert_equal({'to_inherit' => 'val3'}, actual['hostgroup_facet_attributes'])
+    end
+
+    test 'hostgroup facet does not override nil attributes from host' do
+      Facets.register :hostgroup_facet do
+        configure_host TestFacet
+        configure_hostgroup TestHostgroupFacet
+      end
+
+      host = Host::Managed.new
+      hostgroup = FactoryBot.create(:hostgroup, :hostgroup_facet => TestHostgroupFacet.new)
+
+      TestHostgroupFacet.stubs(:attributes_to_inherit).returns([])
+      TestHostgroupFacet.inherit_attributes :to_inherit
+      TestHostgroupFacet.any_instance.stubs(:attributes).returns({:to_inherit => 'val1'})
+
+      actual = host.apply_inherited_attributes('hostgroup' => hostgroup, 'hostgroup_facet_attributes' => { 'to_inherit' => nil })
+
+      assert_equal({'to_inherit' => nil}, actual['hostgroup_facet_attributes'])
+    end
   end
 end