report smaller diffs by dropping null values.

This should result in not showing fields that were unset to begin with,
and mark fields that were explicitly removed as "deleted" instead of
"replaced by ``null``"

changelogs/fragments/smaller-diffs.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - all modules - report smaller diffs by dropping ``null`` values. This should result in not showing fields that were unset to begin with, and mark fields that were explicitly removed as "deleted" instead of "replaced by ``null``"

plugins/module_utils/foreman_helper.py

@@ -946,10 +946,18 @@ def auto_lookup_nested_entities(self):
                             item[nested_key] = self._lookup_entity(item[nested_key], nested_spec)
 
     def record_before(self, resource, entity):
-        self._before[resource].append(entity)
+        if isinstance(entity, dict):
+            to_record = _recursive_dict_without_none(entity)
+        else:
+            to_record = entity
+        self._before[resource].append(to_record)
 
     def record_after(self, resource, entity):
-        self._after[resource].append(entity)
+        if isinstance(entity, dict):
+            to_record = _recursive_dict_without_none(entity)
+        else:
+            to_record = entity
+        self._after[resource].append(to_record)
 
     def record_after_full(self, resource, entity):
         self._after_full[resource].append(entity)

tests/test_playbooks/activation_key.yml

@@ -106,7 +106,7 @@
         expected_change: true
         expected_diff: true
         expected_diff_before: "Test_Organization_Test_Product_Test_Repository.*false"
-        expected_diff_after: "Test_Organization_Test_Product_Test_Repository.*null"
+        expected_diff_after: "content_overrides.*{}"
     - name: update AK with content overrides set to default again, no change
       include_tasks: tasks/activation_key.yml
       vars: