postgresql_set: allow to pass an empty string as a value (#776)

* postgresql_set: allow to pass an empty string as a value

* add check_mode to CI for the case

* add changelog fragment

* add pause

* fix

* fix ci

* fix

* fix

* add suggested

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

@@ -1,3 +1,3 @@
 # Initial CI tests of postgresql_initial module
 - include_tasks: postgresql_set_initial.yml
-  when: postgres_version_resp.stdout is version('9.4', '>=')
+  when: postgres_version_resp.stdout is version('9.6', '>=')

tests/integration/targets/postgresql_set/tasks/postgresql_set_initial.yml

@@ -321,3 +321,55 @@
       that:
       - result is failed
       - result.msg is search('is potentially dangerous')
+
+  ###############################################################################
+  # Bugfix of https://github.com/ansible-collections/community.general/issues/775
+  - name: postgresql_set - turn on archive mode
+    <<: *task_parameters
+    postgresql_set:
+      <<: *pg_parameters
+      name: archive_mode
+      value: 'on'
+
+  - name: Restart PostgreSQL
+    become: yes
+    service:
+      name: "{{ postgresql_service }}"
+      state: restarted
+
+  - name: postgresql_set - set empty string as value
+    <<: *task_parameters
+    postgresql_set:
+      <<: *pg_parameters
+      name: archive_command
+      value: ''
+    register: result
+
+  - assert:
+      that:
+      - result is changed
+
+  - name: postgresql_set - set empty string as value again
+    <<: *task_parameters
+    postgresql_set:
+      <<: *pg_parameters
+      name: archive_command
+      value: ''
+    register: result
+
+  - assert:
+      that:
+      - result is not changed
+
+  - name: postgresql_set - set empty string as value again in check mode
+    <<: *task_parameters
+    postgresql_set:
+      <<: *pg_parameters
+      name: archive_command
+      value: ''
+    register: result
+    check_mode: yes
+
+  - assert:
+      that:
+      - result is not changed