Set default value as empty string for optional str type fields

plugins/modules/nios_vlan.py

@@ -49,19 +49,23 @@
         of this object.  The provided text string will be configured on the
         object instance.
     type: str
+    default: ''
   contact:
     description:
       - Contact information for person/team managing or using VLAN.
     type: str
+    default: ''
   department:
     description:
       - Department where VLAN is used.
     type: str
+    default: ''
   description:
     description:
       - Description for the VLAN object, may be potentially used for
         longer VLAN names.
     type: str
+    default: ''
   reserved:
     description:
       - When set VLAN can only be assigned to IPAM object manually.
@@ -202,10 +206,10 @@ def parent_transform(module):
         name=dict(required=True, ib_req=True),
         id=dict(type='int', required=True, ib_req=True),
         parent=dict(default='default', transform=parent_transform),
-        comment=dict(),
-        contact=dict(),
-        department=dict(),
-        description=dict(),
+        comment=dict(default=''),
+        contact=dict(default=''),
+        department=dict(default=''),
+        description=dict(default=''),
         reserved=dict(type='bool', default=False),
         extattrs=dict(type='dict'),
     )

tests/integration/targets/nios_vlan/tasks/nios_vlan_idempotence.yml

@@ -12,6 +12,7 @@
     name: ansible-vlan
     id: 10
     parent: default
+    comment: 'this is an example comment'
     contact: '[email protected]'
     department: 'IT'
     description: 'This is an example VLAN'
@@ -24,6 +25,7 @@
   infoblox.nios_modules.nios_vlan:
     name: ansible-vlan
     id: 10
+    comment: 'this is an example comment'
     parent: default
     contact: '[email protected]'
     department: 'IT'