handle groups correctly when they are 'null' (#41698)

* handle groups correctly when they are 'null'

 - even if defined as mapping but having no keys, objects shoudl still be processed correctly
 - also add ansilbe_verbosity to vars not to display in ansible-inventory

fixes #41692

(cherry picked from commit 05a49d6eb6)

changelogs/fragments/fix_yaml_inv_nulls.yml

@@ -0,0 +1,2 @@
+bugfixes:
+    - correctly handle yaml inventory files when entries are null dicts https://github.com/ansible/ansible/issues/41692

lib/ansible/cli/inventory.py

@@ -42,6 +42,7 @@ INTERNAL_VARS = frozenset(['ansible_diff_mode',
                            'ansible_playbook_python',
                            'ansible_run_tags',
                            'ansible_skip_tags',
+                           'ansible_verbosity',
                            'ansible_version',
                            'inventory_dir',
                            'inventory_file',

lib/ansible/plugins/inventory/yaml.py

@@ -59,6 +59,7 @@ all: # keys must be unique, i.e. only one 'hosts' per group
 '''
 
 import os
+
 from collections import MutableMapping
 
 from ansible.errors import AnsibleParserError
@@ -112,10 +113,11 @@ class InventoryModule(BaseFileInventoryPlugin):
 
     def _parse_group(self, group, group_data):
 
-        if isinstance(group_data, MutableMapping):
+        if isinstance(group_data, (MutableMapping, type(None))):
 
             self.inventory.add_group(group)
 
+            if group_data is not None:
                 # make sure they are dicts
                 for section in ['vars', 'children', 'hosts']:
                     if section in group_data:
@@ -123,7 +125,7 @@ class InventoryModule(BaseFileInventoryPlugin):
                         if isinstance(group_data[section], string_types):
                             group_data[section] = {group_data[section]: None}
 
-                    if not isinstance(group_data[section], MutableMapping):
+                        if not isinstance(group_data[section], (MutableMapping, type(None))):
                             raise AnsibleParserError('Invalid "%s" entry for "%s" group, requires a dictionary, found "%s" instead.' %
                                                      (section, group, type(group_data[section])))