cronvar: Handle empty value string properly (#10445)

* Fix empty  value issue  in cronvar

* Update changelog

* Update plugins/modules/cronvar.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update changelogs/fragments/10445-cronvar-reject-empty-values.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update tests/integration/targets/cronvar/tasks/main.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update tests/integration/targets/cronvar/tasks/main.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

* Accept empty strings on cronvar

* Update plugins/modules/cronvar.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update main.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit 1f8b5eea4c)

changelogs/fragments/10445-cronvar-reject-empty-values.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - "cronvar - handle empty strings on ``value`` properly  (https://github.com/ansible-collections/community.general/issues/10439, https://github.com/ansible-collections/community.general/pull/10445)."

plugins/modules/cronvar.py

@@ -396,6 +396,8 @@ def main():
     old_value = cronvar.find_variable(name)
 
     if ensure_present:
+        if value == "" and old_value != "":
+            value = '""'
         if old_value is None:
             cronvar.add_variable(name, value, insertbefore, insertafter)
             changed = True

tests/integration/targets/cronvar/tasks/main.yml

@@ -123,6 +123,23 @@
       - custom_varcheck2.stdout == '1'
       - custom_varcheck3.stdout == '0'
 
+
+- name: Add variable with empty string
+  community.general.cronvar:
+    name: EMPTY_VAR
+    value: ""
+    state: present
+
+- name: Assert empty var present
+  ansible.builtin.shell: crontab -l
+  register: result
+  changed_when: false
+
+- name: Assert line is quoted
+  ansible.builtin.assert:
+    that: >-
+      'EMPTY_VAR=""' in result.stdout
+
 - name: Attempt to add cron variable to non-existent parent directory
   cronvar:
     name: NOPARENT_VAR