allow multiple types for null representation (#78451)

* allow multiple types for null representation

  '' is not Nonetype
  fixes #76493

changelogs/fragments/null_means_none.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - null_representation config entry changed to 'raw' as it must allow 'none/null' and empty string.

lib/ansible/config/base.yml

@@ -940,7 +940,7 @@ DEFAULT_NULL_REPRESENTATION:
   env: [{name: ANSIBLE_NULL_REPRESENTATION}]
   ini:
   - {key: null_representation, section: defaults}
-  type: none
+  type: raw
 DEFAULT_POLL_INTERVAL:
   name: Async poll interval
   default: 15

test/integration/targets/template/badnull1.cfg

@@ -0,0 +1,2 @@
+[defaults]
+null_representation = null

test/integration/targets/template/badnull2.cfg

@@ -0,0 +1,2 @@
+[defaults]
+null_representation = ''

test/integration/targets/template/badnull3.cfg

@@ -0,0 +1,2 @@
+[defaults]
+null_representation = none

test/integration/targets/template/runme.sh

@@ -44,3 +44,11 @@ ansible-playbook in_template_overrides.yml -v "$@"
 ansible-playbook lazy_eval.yml -i ../../inventory -v "$@"
 
 ansible-playbook undefined_in_import.yml -i ../../inventory -v "$@"
+
+# ensure diff null configs work #76493
+for badcfg in "badnull1" "badnull2" "badnull3"
+do
+	[ -f "./${badcfg}.cfg" ]
+	ANSIBLE_CONFIG="./${badcfg}.cfg" ansible-config dump --only-changed
+done
+