Fixes #37299 - Fix puppet class assignment

In case the puppet facet does not exist

app/models/concerns/foreman_puppet/extensions/host_common.rb

@@ -9,8 +9,7 @@ def all_puppetclasses(env = environment)
       end
 
       def puppetclasses
-        return ForemanPuppet::Puppetclass.none unless puppet
-        puppet.puppetclasses
+        (puppet || build_puppet).puppetclasses
       end
     end
   end

test/models/foreman_puppet/host_test.rb

@@ -325,5 +325,17 @@ class HostTest < ActiveSupport::TestCase
       h.save!
       assert_empty h.puppet.config_groups
     end
+
+    test 'assign a puppet class to host without puppet facet' do
+      puppet_class = FactoryBot.create(:puppetclass)
+      host = FactoryBot.create(:host)
+      # This would raise the following exception
+      # NoMethodError: undefined method `<<' for #<ActiveRecord::Relation []>
+      host.puppetclasses << puppet_class
+
+      assert_not_nil host.puppet
+      assert_includes host.puppet.puppetclasses, puppet_class
+      assert_includes host.puppetclasses, puppet_class
+    end
   end
 end

test/models/foreman_puppet/hostgroup_test.rb

@@ -10,5 +10,17 @@ class HostgroupTest < ActiveSupport::TestCase
       assert_equal 1, hostgroups.count
       assert_equal hostgroups.pluck(:id).sort, hostgroups.map(&:id).sort
     end
+
+    test 'assign a puppet class to hostgroup without puppet facet' do
+      puppet_class = FactoryBot.create(:puppetclass)
+      hostgroup = FactoryBot.create(:hostgroup)
+      # This would raise the following exception
+      # NoMethodError: undefined method `<<' for #<ActiveRecord::Relation []>
+      hostgroup.puppetclasses << puppet_class
+
+      assert_not_nil hostgroup.puppet
+      assert_includes hostgroup.puppet.puppetclasses, puppet_class
+      assert_includes hostgroup.puppetclasses, puppet_class
+    end
   end
 end