remove bare var handling in conditionals (#51030)

* remove bare var handling in conditionals

  this makes top level and multilevel vars (dicts keys) behave the same
  it will require adding |bool for 'string comparissons' in indirect templates

  - added new tests to ensure uniform handling
  - switched to 'is' testing for status
  - changed warning to 'conditional' as 'when:' is not only place it gets triggered

* updated to include toggle and deprecation

* fix deprecated

* updated tests to handle toggle

* fixed typo and added note about the future

lib/ansible/config/base.yml

@@ -318,6 +318,19 @@ COLOR_WARN:
   env: [{name: ANSIBLE_COLOR_WARN}]
   ini:
   - {key: warn, section: colors}
+CONDITINAL_BARE_VARS:
+  name: Allow bare variable evaluation in conditionals
+  default: True
+  type: boolean
+  description:
+    - With this setting on (True), runing conditional evaluation 'var' is treated differently 'var.subkey' as the first is evaluted
+      directly while the second goes though the Jinja2 parser. But 'false' strings in 'var' get evaluated as booleans.
+    - With this settting off they both evalutate the same but in cases in which 'var' was 'false' (a string) it won't get evaluated as a boolean anymore.
+    - Currently this setting defaults to 'True' but will soon change to 'False' and the setting itself will be removed in the future.
+    - Expect the default to change in version 2.10 and that this setting eventually will be deprecated after 2.12
+  env: [{name: ANSIBLE_CONDITIONAL_BARE_VARS}]
+  ini:
+  - {key: conditional_bare_variables, section: defaults}
 ACTION_WARNINGS:
   name: Toggle action warnings
   default: True

lib/ansible/playbook/conditional.py

@@ -25,6 +25,7 @@ import re
 from jinja2.compiler import generate
 from jinja2.exceptions import UndefinedError
 
+from ansible import constants as C
 from ansible.errors import AnsibleError, AnsibleUndefinedVariable
 from ansible.module_utils.six import text_type
 from ansible.module_utils._text import to_native
@@ -113,21 +114,16 @@ class Conditional:
         if isinstance(conditional, bool):
             return conditional
 
+        if C.CONDITINAL_BARE_VARS:
+            if conditional in all_vars and VALID_VAR_REGEX.match(conditional):
+                display.deprecated('evaluating %s as a bare variable, this behaviour will go away and you might need to add |bool'
+                                   ' to the expression in the future. Also see CONDITIONAL_BARE_VARS configuration toggle.' % conditional, "2.12")
+                conditional = all_vars[conditional]
+
         if templar.is_template(conditional):
-            display.warning('when statements should not include jinja2 '
+            display.warning('conditional statements should not include jinja2 '
                             'templating delimiters such as {{ }} or {%% %%}. '
                             'Found: %s' % conditional)
-
-        # pull the "bare" var out, which allows for nested conditionals
-        # and things like:
-        # - assert:
-        #     that:
-        #     - item
-        #   with_items:
-        #   - 1 == 1
-        if conditional in all_vars and VALID_VAR_REGEX.match(conditional):
-            conditional = all_vars[conditional]
-
         # make sure the templar is using the variables specified with this method
         templar.set_available_variables(variables=all_vars)
 
@@ -219,5 +215,5 @@ class Conditional:
                 # as nothing above matched the failed var name, re-raise here to
                 # trigger the AnsibleUndefinedVariable exception again below
                 raise
-            except Exception as new_e:
+            except Exception:
                 raise AnsibleUndefinedVariable("error while evaluating conditional (%s): %s" % (original, e))