do not error in case of empty list constructed group (#53748)

lib/ansible/plugins/inventory/__init__.py

@@ -429,7 +429,9 @@ class Constructable(object):
                                 self.inventory.add_child(parent_name, result_gname)
 
                     else:
-                        if strict:
-                            raise AnsibleParserError("No key or key resulted empty, invalid entry")
+                        # exclude case of empty list and dictionary, because these are valid constructions
+                        # simply no groups need to be constructed, but are still falsy
+                        if strict and key not in ([], {}):
+                            raise AnsibleParserError("No key or key resulted empty for %s in host %s, invalid entry" % (keyed.get('key'), host))
                 else:
                     raise AnsibleParserError("Invalid keyed group entry, it must be a dictionary: %s " % keyed)

test/units/plugins/inventory/test_constructed.py

@@ -24,7 +24,7 @@ from ansible.inventory.data import InventoryData
 from ansible.template import Templar
 
 
-@pytest.fixture(scope="module")
+@pytest.fixture()
 def inventory_module():
     r = InventoryModule()
     r.inventory = InventoryData()
@@ -60,13 +60,11 @@ def test_keyed_group_separator(inventory_module):
         {
             'prefix': 'farmer',
             'separator': '_old_',
-            'key': 'farmer',
-            'unsafe': True
+            'key': 'farmer'
         },
         {
             'separator': 'mmmmmmmmmm',
-            'key': 'barn',
-            'unsafe': True
+            'key': 'barn'
         }
     ]
     inventory_module._add_host_to_keyed_groups(
@@ -78,6 +76,22 @@ def test_keyed_group_separator(inventory_module):
         assert group.hosts == [host]
 
 
+def test_keyed_group_empty_construction(inventory_module):
+    inventory_module.inventory.add_host('farm')
+    inventory_module.inventory.set_variable('farm', 'barn', {})
+    host = inventory_module.inventory.get_host('farm')
+    keyed_groups = [
+        {
+            'separator': 'mmmmmmmmmm',
+            'key': 'barn'
+        }
+    ]
+    inventory_module._add_host_to_keyed_groups(
+        keyed_groups, host.vars, host.name, strict=True
+    )
+    assert host.groups == []
+
+
 def test_keyed_parent_groups(inventory_module):
     inventory_module.inventory.add_host('web1')
     inventory_module.inventory.add_host('web2')