fix precedence issue with facts and vars (#32302)

avoid making gathered facts high precedence, only set_fact is supposed to be.
vars set via set_fact with cacheable are higher precedence than plain facts.

Previously (after 6fbd0a8bb5) regular facts would end up with a
higher precedence than host or play vars, but they should not be. Facts were getting added to 'non_persistent_facts' (equivalent to 'register' vars) which is higher precedence than facts should be.

added 'cacheable set_facts' to precedence docs

'ansible_facts_cacheable' ->  '_ansible_facts_cacheable' (made 'private')

docs/docsite/rst/playbooks_variables.rst

@@ -865,7 +865,7 @@ In 2.x, we have made the order of precedence more specific (with the last listed
   * inventory file or script host vars [2]_
   * inventory host_vars/*
   * playbook host_vars/*
-  * host facts
+  * host facts / cached set_facts [3]_
   * play vars
   * play vars_prompt
   * play vars_files
@@ -884,6 +884,8 @@ Basically, anything that goes into "role defaults" (the defaults folder inside t
 
 .. [1] Tasks in each role will see their own role's defaults. Tasks defined outside of a role will see the last role's defaults.
 .. [2] Variables defined in inventory file or provided by dynamic inventory.
+.. [3] When created with set_facts's cacheable option, variables will have the high precedence in the play,
+       but will be the same as a host facts precedence when they come from the cache.
 
 .. note:: Within any section, redefining a var will overwrite the previous instance.
           If multiple groups have the same variable, the last one loaded wins.

lib/ansible/plugins/action/set_fact.py

@@ -54,5 +54,5 @@ class ActionModule(ActionBase):
 
         result['changed'] = False
         result['ansible_facts'] = facts
-        result['ansible_facts_cacheable'] = cacheable
+        result['_ansible_facts_cacheable'] = cacheable
         return result

lib/ansible/plugins/strategy/__init__.py

@@ -511,13 +511,12 @@ class StrategyBase:
                                 for target_host in host_list:
                                     self._variable_manager.set_host_variable(target_host, var_name, var_value)
                         else:
-                            cacheable = result_item.pop('ansible_facts_cacheable', True)
+                            cacheable = result_item.pop('_ansible_facts_cacheable', False)
                             for target_host in host_list:
-                                if cacheable:
+                                if not original_task.action == 'set_fact' or cacheable:
                                     self._variable_manager.set_host_facts(target_host, result_item['ansible_facts'].copy())
-
-                                # If we are setting a fact, it should populate non_persistent_facts as well
-                                self._variable_manager.set_nonpersistent_facts(target_host, result_item['ansible_facts'].copy())
+                                if original_task.action == 'set_fact':
+                                    self._variable_manager.set_nonpersistent_facts(target_host, result_item['ansible_facts'].copy())
 
                     if 'ansible_stats' in result_item and 'data' in result_item['ansible_stats'] and result_item['ansible_stats']['data']: