Cache items when task.loop/with_items is evaluated to set delegate_to vars (#41969)

* If we evaluate task.loop/with_items when calculating delegate_to vars, cache the items. Fixes #28231

* Add comments about caching loop items

* Add test for delegate_to+loop+random

* Be more careful about where we update task.loop

lib/ansible/vars/manager.py

@@ -498,10 +498,19 @@ class VariableManager:
                     # This task will be skipped later due to this, so we just setup
                     # a dummy array for the later code so it doesn't fail
                     items = [None]
+                # Update task.loop with templated items, this ensures that delegate_to+loop
+                # doesn't produce different restuls than TaskExecutor which may reprocess the loop
+                # Set loop_with to None, so we don't do extra unexpected processing on the cached items later
+                # in TaskExecutor
+                task.loop_with = None
+                task.loop = items
             else:
                 raise AnsibleError("Failed to find the lookup named '%s' in the available lookup plugins" % task.loop_with)
         elif task.loop is not None:
             items = templar.template(task.loop)
+            # Update task.loop with templated items, this ensures that delegate_to+loop
+            # doesn't produce different restuls than TaskExecutor which may reprocess the loop
+            task.loop = items
         else:
             items = [None]