Inventory plugin for empty group creation

ansible.cfg

@@ -12,4 +12,4 @@ use_persistent_connections      = true
 usetty                          = false
 
 [inventory]
-enable_plugins = constructed, community.general.proxmox, yaml
+enable_plugins = constructed, community.general.proxmox, group_creator, yaml

inventory_plugins/group_creator.py

@@ -0,0 +1,107 @@
+import os
+
+from ansible import constants as C
+from ansible.errors import AnsibleParserError
+from ansible.module_utils._text import to_native
+from ansible.plugins.inventory import BaseInventoryPlugin
+
+
+DOCUMENTATION = """
+    name: group_creator
+    short_description: Uses Jinja2 templates to construct empty groups.
+    description:
+    - Uses a YAML configuration file with a valid YAML extension to define
+      groups. The groups' names as well as the list of parent groups for a
+      given group may use Jinja2 templates based on the host variables.
+    options:
+      plugin:
+        description:
+        - Token that ensures this is a source file for the C(group_creator)
+          plugin.
+        required: True
+        choices: ['group_creator']
+      groups:
+        description:
+        - The list of groups to create.
+        type: list
+        elements: dict
+        required: True
+        suboptions:
+          name:
+            description:
+            - The template to generate a group name from. If an empty
+              string is returned, the group will not be created.
+            type: str
+            required: true
+          parents:
+            description:
+            - A list of templates to generate the names of the group's
+              parents from. Empty strings will be ignored.
+            type: list
+            elements: str
+            default: []
+      strict:
+          description:
+          - If C(yes) make invalid templates a fatal error, otherwise skip and
+            continue.
+          required: False
+          type: bool
+          default: no
+"""
+
+
+class InventoryModule(BaseInventoryPlugin):
+    """Constructs empty groups based on arbitrary variables."""
+
+    NAME = "group_creator"
+
+    def __init__(self):
+        super(InventoryModule, self).__init__()
+
+    def verify_file(self, path):
+        valid = False
+        if super(InventoryModule, self).verify_file(path):
+            file_name, ext = os.path.splitext(path)
+            if not ext or ext in ['.config'] + C.YAML_FILENAME_EXTENSIONS:
+                valid = True
+        return valid
+
+    def _evaluate(self, template, variables, auto_template):
+        t = self.templar
+        if auto_template:
+            template = "%s%s%s" % (
+                t.environment.variable_start_string,
+                template,
+                t.environment.variable_end_string,
+            )
+        t.available_variables = variables
+        return t.template(template, disable_lookups=True)
+
+    def _get_group_name(self, host, name, host_vars, strict):
+        try:
+            name = self._evaluate(name, host_vars, False)
+            return self._sanitize_group_name(name)
+        except Exception as e:
+            if strict:
+                raise AnsibleParserError(
+                    "Could not generate group name for host %s from '%s': (%s) %s"
+                    % (host, name, to_native(repr(type(e))), to_native(e))
+                )
+            return ""
+
+    def parse(self, inventory, loader, path, cache=False):
+        super(InventoryModule, self).parse(inventory, loader, path, cache=cache)
+        self._read_config_data(path)
+        strict = self.get_option("strict")
+        for host in inventory.hosts:
+            host_vars = self.inventory.get_host(host).get_vars()
+            for group in self.get_option("groups"):
+                name = self._get_group_name(host, group['name'], host_vars, strict)
+                if not name:
+                    continue
+                self.inventory.add_group(name)
+                for ptmpl in group.get("parents"):
+                    parent = self._get_group_name(host, ptmpl, host_vars, strict)
+                    if parent:
+                        self.inventory.add_group(parent)
+                        self.inventory.add_child(parent, name)