Remove deprecated vars keyword syntax as a list of dictionaries, it is now required to be a single dictionary (#82980)

Update unit test

changelogs/fragments/remove-deprecated-vars-syntax.yml

@@ -0,0 +1,2 @@
+removed_features:
+  - Removed support for setting the ``vars`` keyword to lists of dictionaries. It is now required to be a single dictionary.

lib/ansible/playbook/base.py

@@ -574,9 +574,7 @@ class FieldAttributeBase:
 
     def _load_vars(self, attr, ds):
         '''
-        Vars in a play can be specified either as a dictionary directly, or
-        as a list of dictionaries. If the later, this method will turn the
-        list into a single dictionary.
+        Vars in a play must be specified as a dictionary.
         '''
 
         def _validate_variable_keys(ds):
@@ -588,21 +586,6 @@ class FieldAttributeBase:
             if isinstance(ds, dict):
                 _validate_variable_keys(ds)
                 return combine_vars(self.vars, ds)
-            elif isinstance(ds, list):
-                display.deprecated(
-                    (
-                        'Specifying a list of dictionaries for vars is deprecated in favor of '
-                        'specifying a dictionary.'
-                    ),
-                    version='2.18'
-                )
-                all_vars = self.vars
-                for item in ds:
-                    if not isinstance(item, dict):
-                        raise ValueError
-                    _validate_variable_keys(item)
-                    all_vars = combine_vars(all_vars, item)
-                return all_vars
             elif ds is None:
                 return {}
             else:

test/sanity/ignore.txt

@@ -196,7 +196,6 @@ test/units/cli/test_data/role_skeleton/README.md pymarkdown:line-length
 test/integration/targets/find/files/hello_world.gbk no-smart-quotes
 test/integration/targets/find/files/hello_world.gbk no-unwanted-characters
 lib/ansible/galaxy/collection/__init__.py pylint:ansible-deprecated-version-comment  # 2.18 deprecation
-lib/ansible/playbook/base.py pylint:ansible-deprecated-version  # 2.18 deprecation
 lib/ansible/playbook/play.py pylint:ansible-deprecated-version  # 2.18 deprecation
 lib/ansible/playbook/play_context.py pylint:ansible-deprecated-version  # 2.18 deprecation
 lib/ansible/plugins/action/__init__.py pylint:ansible-deprecated-version  # 2.18 deprecation

test/units/playbook/test_base.py

@@ -198,8 +198,7 @@ class TestBase(unittest.TestCase):
               'vars': [{'var_2_key': 'var_2_value'},
                        {'var_1_key': 'var_1_value'}]
               }
-        b = self._base_validate(ds)
-        self.assertEqual(b.vars['var_1_key'], 'var_1_value')
+        self.assertRaises(AnsibleParserError, self.b.load_data, ds)
 
     def test_vars_not_dict_or_list(self):
         ds = {'environment': [],