Add a Singleton metaclass, use it with Display (#48935)

* Add a Singleton class, use it with Display

* update six import

* Move remaining failes to display singleton

* Fix rebase issues

* Singleton improvements

* Add code-smell for 'from __main__ import display'. ci_complete

* s/self/cls/g

* Add docs for no-main-display

* Address linting issues

* Add changelog fragment. ci_complete

* Implement reentrant lock for class instantiation in Singleton

* Add Display singleton porting guide

lib/ansible/executor/module_common.py

@@ -42,12 +42,9 @@ from ansible.plugins.loader import module_utils_loader
 # variable to the object and then it never gets updated.
 from ansible.executor import action_write_locks
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+from ansible.utils.display import Display
 
+display = Display()
 
 REPLACER = b"#<<INCLUDE_ANSIBLE_MODULE_COMMON>>"
 REPLACER_VERSION = b"\"<<ANSIBLE_VERSION>>\""

lib/ansible/executor/play_iterator.py

@@ -26,13 +26,10 @@ from ansible.module_utils.six import iteritems
 from ansible.module_utils.parsing.convert_bool import boolean
 from ansible.playbook.block import Block
 from ansible.playbook.task import Task
+from ansible.utils.display import Display
 
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 __all__ = ['PlayIterator']

lib/ansible/executor/playbook_executor.py

@@ -30,12 +30,9 @@ from ansible.utils.helpers import pct_to_int
 from ansible.module_utils.parsing.convert_bool import boolean
 from ansible.utils.path import makedirs_safe
 from ansible.utils.ssh_functions import check_for_controlpersist
+from ansible.utils.display import Display
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 class PlaybookExecutor:

lib/ansible/executor/process/worker.py

@@ -40,15 +40,12 @@ from ansible.errors import AnsibleConnectionFailure
 from ansible.executor.task_executor import TaskExecutor
 from ansible.executor.task_result import TaskResult
 from ansible.module_utils._text import to_text
-
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+from ansible.utils.display import Display
 
 __all__ = ['WorkerProcess']
 
+display = Display()
+
 
 class WorkerProcess(multiprocessing.Process):
     '''

lib/ansible/executor/task_executor.py

@@ -25,13 +25,10 @@ from ansible.template import Templar
 from ansible.utils.listify import listify_lookup_plugin_terms
 from ansible.utils.unsafe_proxy import UnsafeProxy, wrap_var
 from ansible.vars.clean import namespace_facts, clean_facts
+from ansible.utils.display import Display
 from ansible.utils.vars import combine_vars
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 __all__ = ['TaskExecutor']

lib/ansible/executor/task_queue_manager.py

@@ -38,16 +38,13 @@ from ansible.template import Templar
 from ansible.utils.helpers import pct_to_int
 from ansible.vars.hostvars import HostVars
 from ansible.vars.reserved import warn_if_reserved
-
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+from ansible.utils.display import Display
 
 
 __all__ = ['TaskQueueManager']
 
+display = Display()
+
 
 class TaskQueueManager: