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/playbook/__init__.py

@@ -27,12 +27,9 @@ from ansible.module_utils._text import to_text, to_native
 from ansible.playbook.play import Play
 from ansible.playbook.playbook_include import PlaybookInclude
 from ansible.plugins.loader import get_all_plugin_loaders
+from ansible.utils.display import Display
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 __all__ = ['Playbook']

lib/ansible/playbook/base.py

@@ -21,12 +21,9 @@ from ansible.module_utils._text import to_text, to_native
 from ansible.playbook.attribute import Attribute, FieldAttribute
 from ansible.parsing.dataloader import DataLoader
 from ansible.utils.vars import combine_vars, isidentifier, get_unique_id
+from ansible.utils.display import Display
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 def _generic_g(prop_name, self):

lib/ansible/playbook/become.py

@@ -22,12 +22,9 @@ __metaclass__ = type
 from ansible import constants as C
 from ansible.errors import AnsibleParserError
 from ansible.playbook.attribute import FieldAttribute
+from ansible.utils.display import Display
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 class Become:

lib/ansible/playbook/conditional.py

@@ -29,13 +29,9 @@ from ansible.errors import AnsibleError, AnsibleUndefinedVariable
 from ansible.module_utils.six import text_type
 from ansible.module_utils._text import to_native
 from ansible.playbook.attribute import FieldAttribute
+from ansible.utils.display import Display
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
-
+display = Display()
 
 DEFINED_REGEX = re.compile(r'(hostvars\[.+\]|[\w_]+)\s+(not\s+is|is|is\s+not)\s+(defined|undefined)')
 LOOKUP_REGEX = re.compile(r'lookup\s*\(')

lib/ansible/playbook/helpers.py

@@ -25,12 +25,9 @@ from ansible.errors import AnsibleParserError, AnsibleUndefinedVariable, Ansible
 from ansible.module_utils._text import to_native
 from ansible.module_utils.six import string_types
 from ansible.parsing.mod_args import ModuleArgsParser
+from ansible.utils.display import Display
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 def load_list_of_blocks(ds, play, parent_block=None, role=None, task_include=None, use_handlers=False, variable_manager=None, loader=None):

lib/ansible/playbook/included_file.py

@@ -24,12 +24,9 @@ import os
 from ansible.playbook.task_include import TaskInclude
 from ansible.playbook.role_include import IncludeRole
 from ansible.template import Templar
+from ansible.utils.display import Display
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 class IncludedFile:

lib/ansible/playbook/play.py

@@ -30,12 +30,9 @@ from ansible.playbook.helpers import load_list_of_blocks, load_list_of_roles
 from ansible.playbook.role import Role
 from ansible.playbook.taggable import Taggable
 from ansible.vars.manager import preprocess_vars
+from ansible.utils.display import Display
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 __all__ = ['Play']

lib/ansible/playbook/play_context.py

@@ -37,14 +37,11 @@ from ansible.module_utils.parsing.convert_bool import boolean
 from ansible.playbook.attribute import FieldAttribute
 from ansible.playbook.base import Base
 from ansible.plugins import get_plugin_class
+from ansible.utils.display import Display
 from ansible.utils.ssh_functions import check_for_controlpersist
 
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 __all__ = ['PlayContext']

lib/ansible/playbook/role/definition.py

@@ -32,16 +32,12 @@ from ansible.playbook.conditional import Conditional
 from ansible.playbook.taggable import Taggable
 from ansible.template import Templar
 from ansible.utils.path import unfrackpath
-
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
-
+from ansible.utils.display import Display
 
 __all__ = ['RoleDefinition']
 
+display = Display()
+
 
 class RoleDefinition(Base, Become, Conditional, Taggable):
 

lib/ansible/playbook/role/requirement.py

@@ -31,11 +31,10 @@ from ansible.module_utils._text import to_native
 from ansible.module_utils.common.process import get_bin_path
 from ansible.module_utils.six import string_types
 from ansible.playbook.role.definition import RoleDefinition
-
+from ansible.utils.display import Display
 
 __all__ = ['RoleRequirement']
 
-
 VALID_SPEC_KEYS = [
     'name',
     'role',
@@ -44,11 +43,7 @@ VALID_SPEC_KEYS = [
     'version',
 ]
 
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+display = Display()
 
 
 class RoleRequirement(RoleDefinition):

lib/ansible/playbook/role_include.py

@@ -1,4 +1,3 @@
-
 #
 # This file is part of Ansible
 #
@@ -27,15 +26,12 @@ from ansible.playbook.block import Block
 from ansible.playbook.task_include import TaskInclude
 from ansible.playbook.role import Role
 from ansible.playbook.role.include import RoleInclude
-
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+from ansible.utils.display import Display
 
 __all__ = ['IncludeRole']
 
+display = Display()
+
 
 class IncludeRole(TaskInclude):
 

lib/ansible/playbook/task.py

@@ -36,16 +36,12 @@ from ansible.playbook.conditional import Conditional
 from ansible.playbook.loop_control import LoopControl
 from ansible.playbook.role import Role
 from ansible.playbook.taggable import Taggable
-
-
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+from ansible.utils.display import Display
 
 __all__ = ['Task']
 
+display = Display()
+
 
 class Task(Base, Conditional, Taggable, Become):
 

lib/ansible/playbook/task_include.py

@@ -24,15 +24,12 @@ from ansible.errors import AnsibleParserError
 from ansible.playbook.attribute import FieldAttribute
 from ansible.playbook.block import Block
 from ansible.playbook.task import Task
-
-try:
-    from __main__ import display
-except ImportError:
-    from ansible.utils.display import Display
-    display = Display()
+from ansible.utils.display import Display
 
 __all__ = ['TaskInclude']
 
+display = Display()
+
 
 class TaskInclude(Task):