refactor: Move NoneType to sphinx.util.typing

CHANGES

@@ -120,6 +120,7 @@ Deprecated
 * ``sphinx.util.osutil.EPIPE``
 * ``sphinx.util.osutil.walk()``
 * ``sphinx.util.PeekableIterator``
+* ``sphinx.util.pycompat.NoneType``
 * ``sphinx.util.pycompat.TextIOWrapper``
 * ``sphinx.util.pycompat.UnicodeMixin``
 * ``sphinx.util.pycompat.htmlescape``

doc/extdev/index.rst

@@ -420,6 +420,11 @@ The following is a list of deprecated interfaces.
      - 4.0
      - ``os.walk()``
 
+   * - ``sphinx.util.pycompat.NoneType``
+     - 2.0
+     - 4.0
+     - ``sphinx.util.typing.NoneType``
+
    * - ``sphinx.util.pycompat.TextIOWrapper``
      - 2.0
      - 4.0

sphinx/config.py

@@ -22,7 +22,8 @@ from sphinx.locale import _, __
 from sphinx.util import logging
 from sphinx.util.i18n import format_date
 from sphinx.util.osutil import cd
-from sphinx.util.pycompat import execfile_, NoneType
+from sphinx.util.pycompat import execfile_
+from sphinx.util.typing import NoneType
 
 if False:
     # For type annotation

sphinx/util/inspect.py

@@ -20,7 +20,7 @@ from io import StringIO
 
 from sphinx.deprecation import RemovedInSphinx30Warning
 from sphinx.util import logging
-from sphinx.util.pycompat import NoneType
+from sphinx.util.typing import NoneType
 
 if False:
     # For type annotation

sphinx/util/pycompat.py

@@ -18,7 +18,7 @@ from sphinx.deprecation import RemovedInSphinx40Warning, deprecated_alias
 from sphinx.locale import __
 from sphinx.util import logging
 from sphinx.util.console import terminal_safe
-
+from sphinx.util.typing import NoneType
 
 if False:
     # For type annotation
@@ -28,8 +28,6 @@ if False:
 logger = logging.getLogger(__name__)
 
 
-NoneType = type(None)
-
 # ------------------------------------------------------------------------------
 # Python 2/3 compatibility
 
@@ -95,6 +93,7 @@ def execfile_(filepath, _globals, open=open):
 
 deprecated_alias('sphinx.util.pycompat',
                  {
+                     'NoneType': NoneType,  # type: ignore
                      'TextIOWrapper': io.TextIOWrapper,
                      'htmlescape': html.escape,
                      'indent': textwrap.indent,

sphinx/util/typing.py

@@ -20,6 +20,9 @@ DirectiveOption = Callable[[str], Any]
 # Text like nodes which are initialized with text and rawsource
 TextlikeNode = Union[nodes.Text, nodes.TextElement]
 
+# type of None
+NoneType = type(None)
+
 # common role functions
 RoleFunction = Callable[[str, str, str, int, Inliner, Dict, List[str]],
                         Tuple[List[nodes.Node], List[nodes.system_message]]]