Repository: ansible/ansible

Issue:
YAML Inventory Parsing Issue
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##### SUMMARY
In Ansible 2.6 RC3 we are seeing an issue where the YAML inventory parser is not correctly identifying groups.  Eg, for this inventory file:
```
---
group1:
  children:
    group2:

group2:
  hosts:
    host1:
    host2:
```
Running "ansible group1 --list-hosts" complains about "group2":
```
 [WARNING]: Skipping 'group2' as this is not a valid group definition

 [WARNING]: No hosts matched, nothing to do

  hosts (0):
```


##### ISSUE TYPE
 - Bug Report

##### COMPONENT NAME
<!--- Insert, BELOW THIS COMMENT, the name of the module, plugin, task or feature.
Do not include extra details here, e.g. "vyos_command" not "the network module vyos_command" or the full path-->

##### ANSIBLE VERSION
<!--- Paste, BELOW THIS COMMENT, verbatim output from "ansible --version" between quotes below -->
```
ansible 2.6.0rc3
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /bin/ansible
  python version = 2.7.5 (default, Aug  4 2017, 00:39:18) [GCC 4.8.5 20150623 (Red Hat 4.8.5-16)]

```

##### CONFIGURATION
<!--- If using Ansible 2.4 or above, paste, BELOW THIS COMMENT, the results of "ansible-config dump --only-changed"
Otherwise, mention any settings you have changed/added/removed in ansible.cfg
(or using the ANSIBLE_* environment variables).-->
```
DEFAULT_HOST_LIST(/etc/ansible/ansible.cfg) = [u'/etc/ansible/hosts.yml']
```
##### OS / ENVIRONMENT
<!--- Mention, BELOW THIS COMMENT, the OS you are running Ansible from, and the OS you are
managing, or say "N/A" for anything that is not platform-specific.
Also mention the specific version of what you are trying to control,
e.g. if this is a network bug the version of firmware on the network device.-->

CentOS Linux release 7.4.1708 (Core)

##### STEPS TO REPRODUCE
<!--- For bugs, show exactly how to reproduce the problem, using a minimal test-case.
For new features, show how the feature would be used. -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml
# cat hosts.yml
---
group1:
  children:
    group2:

group2:
  hosts:
    host1:
    host2:


```

<!--- You can also paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- What did you expect to happen when running the steps above? -->

With Ansible 2.4 and 2.5 we get these results:
```
# ansible group1 --list-hosts
  hosts (2):
    host2
    host1
```
##### ACTUAL RESULTS
<!--- What actually happened? If possible run with extra verbosity (-vvvv) -->

With ansible 2.6 we get these results:
```
# ansible group1 --list-hosts -vvv
ansible 2.6.0rc3
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /bin/ansible
  python version = 2.7.5 (default, Aug  4 2017, 00:39:18) [GCC 4.8.5 20150623 (Red Hat 4.8.5-16)]
Using /etc/ansible/ansible.cfg as config file
 [WARNING]: Skipping 'group2' as this is not a valid group definition

Parsed /etc/ansible/hosts.yml inventory source with ini plugin
 [WARNING]: No hosts matched, nothing to do

  hosts (0):
```
<!--- Paste verbatim command output between quotes below -->
```

```



Discussion:

Resolving patch:
diff --git a/lib/ansible/cli/inventory.py b/lib/ansible/cli/inventory.py
--- a/lib/ansible/cli/inventory.py
+++ b/lib/ansible/cli/inventory.py
@@ -42,6 +42,7 @@
                            'ansible_playbook_python',
                            'ansible_run_tags',
                            'ansible_skip_tags',
+                           'ansible_verbosity',
                            'ansible_version',
                            'inventory_dir',
                            'inventory_file',
diff --git a/lib/ansible/plugins/inventory/yaml.py b/lib/ansible/plugins/inventory/yaml.py
--- a/lib/ansible/plugins/inventory/yaml.py
+++ b/lib/ansible/plugins/inventory/yaml.py
@@ -59,6 +59,7 @@
 '''
 
 import os
+
 from collections import MutableMapping
 
 from ansible.errors import AnsibleParserError
@@ -112,37 +113,38 @@ def parse(self, inventory, loader, path, cache=True):
 
     def _parse_group(self, group, group_data):
 
-        if isinstance(group_data, MutableMapping):
+        if isinstance(group_data, (MutableMapping, type(None))):
 
             self.inventory.add_group(group)
 
-            # make sure they are dicts
-            for section in ['vars', 'children', 'hosts']:
-                if section in group_data:
-                    # convert strings to dicts as these are allowed
-                    if isinstance(group_data[section], string_types):
-                        group_data[section] = {group_data[section]: None}
-
-                    if not isinstance(group_data[section], MutableMapping):
-                        raise AnsibleParserError('Invalid "%s" entry for "%s" group, requires a dictionary, found "%s" instead.' %
-                                                 (section, group, type(group_data[section])))
-
-            for key in group_data:
-                if key == 'vars':
-                    for var in group_data['vars']:
-                        self.inventory.set_variable(group, var, group_data['vars'][var])
-
-                elif key == 'children':
-                    for subgroup in group_data['children']:
-                        self._parse_group(subgroup, group_data['children'][subgroup])
-                        self.inventory.add_child(group, subgroup)
-
-                elif key == 'hosts':
-                    for host_pattern in group_data['hosts']:
-                        hosts, port = self._parse_host(host_pattern)
-                        self._populate_host_vars(hosts, group_data['hosts'][host_pattern] or {}, group, port)
-                else:
-                    self.display.warning('Skipping unexpected key (%s) in group (%s), only "vars", "children" and "hosts" are valid' % (key, group))
+            if group_data is not None:
+                # make sure they are dicts
+                for section in ['vars', 'children', 'hosts']:
+                    if section in group_data:
+                        # convert strings to dicts as these are allowed
+                        if isinstance(group_data[section], string_types):
+                            group_data[section] = {group_data[section]: None}
+
+                        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])))
+
+                for key in group_data:
+                    if key == 'vars':
+                        for var in group_data['vars']:
+                            self.inventory.set_variable(group, var, group_data['vars'][var])
+
+                    elif key == 'children':
+                        for subgroup in group_data['children']:
+                            self._parse_group(subgroup, group_data['children'][subgroup])
+                            self.inventory.add_child(group, subgroup)
+
+                    elif key == 'hosts':
+                        for host_pattern in group_data['hosts']:
+                            hosts, port = self._parse_host(host_pattern)
+                            self._populate_host_vars(hosts, group_data['hosts'][host_pattern] or {}, group, port)
+                    else:
+                        self.display.warning('Skipping unexpected key (%s) in group (%s), only "vars", "children" and "hosts" are valid' % (key, group))
 
         else:
             self.display.warning("Skipping '%s' as this is not a valid group definition" % group)


Test patch: