Clean up distutils_scheme types (#7300)

Author: pradyunsg

src/pip/_internal/locations.py

@@ -14,14 +14,17 @@
 import sysconfig
 from distutils import sysconfig as distutils_sysconfig
 from distutils.command.install import SCHEME_KEYS  # type: ignore
+from distutils.command.install import install as distutils_install_command
 
 from pip._internal.utils import appdirs
 from pip._internal.utils.compat import WINDOWS
-from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING, cast
 from pip._internal.utils.virtualenv import running_under_virtualenv
 
 if MYPY_CHECK_RUNNING:
-    from typing import Any, Union, Dict, List, Optional
+    from typing import Dict, List, Optional, Union
+
+    from distutils.cmd import Command as DistutilsCommand
 
 
 # Application Directories
@@ -88,29 +91,25 @@ def get_src_prefix():
         bin_py = '/usr/local/bin'
 
 
-def distutils_scheme(dist_name, user=False, home=None, root=None,
-                     isolated=False, prefix=None):
+def distutils_scheme(
+    dist_name, user=False, home=None, root=None, isolated=False, prefix=None
+):
     # type:(str, bool, str, str, bool, str) -> dict
     """
     Return a distutils install scheme
     """
     from distutils.dist import Distribution
 
-    scheme = {}
-
-    if isolated:
-        extra_dist_args = {"script_args": ["--no-user-cfg"]}
-    else:
-        extra_dist_args = {}
     dist_args = {'name': dist_name}  # type: Dict[str, Union[str, List[str]]]
-    dist_args.update(extra_dist_args)
+    if isolated:
+        dist_args["script_args"] = ["--no-user-cfg"]
 
     d = Distribution(dist_args)
-    # Ignoring, typeshed issue reported python/typeshed/issues/2567
     d.parse_config_files()
-    # NOTE: Ignoring type since mypy can't find attributes on 'Command'
-    i = d.get_command_obj('install', create=True)  # type: Any
-    assert i is not None
+    obj = None  # type: Optional[DistutilsCommand]
+    obj = d.get_command_obj('install', create=True)
+    assert obj is not None
+    i = cast(distutils_install_command, obj)
     # NOTE: setting user or home has the side-effect of creating the home dir
     # or user base for installations during finalize_options()
     # ideally, we'd prefer a scheme class that has no side-effects.
@@ -123,6 +122,8 @@ def distutils_scheme(dist_name, user=False, home=None, root=None,
     i.home = home or i.home
     i.root = root or i.root
     i.finalize_options()
+
+    scheme = {}
     for key in SCHEME_KEYS:
         scheme[key] = getattr(i, 'install_' + key)
 
@@ -131,9 +132,7 @@ def distutils_scheme(dist_name, user=False, home=None, root=None,
     # platlib).  Note, i.install_lib is *always* set after
     # finalize_options(); we only want to override here if the user
     # has explicitly requested it hence going back to the config
-
-    # Ignoring, typeshed issue reported python/typeshed/issues/2567
-    if 'install_lib' in d.get_option_dict('install'):  # type: ignore
+    if 'install_lib' in d.get_option_dict('install'):
         scheme.update(dict(purelib=i.install_lib, platlib=i.install_lib))
 
     if running_under_virtualenv():

src/pip/_internal/utils/filesystem.py

@@ -13,8 +13,7 @@
 from pip._vendor.six import PY2
 
 from pip._internal.utils.compat import get_path_uid
-from pip._internal.utils.misc import cast
-from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING, cast
 
 if MYPY_CHECK_RUNNING:
     from typing import BinaryIO, Iterator

src/pip/_internal/utils/misc.py

@@ -40,7 +40,7 @@
     str_to_display,
 )
 from pip._internal.utils.marker_files import write_delete_marker_file
-from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING, cast
 from pip._internal.utils.virtualenv import (
     running_under_virtualenv,
     virtualenv_no_global,
@@ -54,16 +54,11 @@
 if MYPY_CHECK_RUNNING:
     from typing import (
         Any, AnyStr, Container, Iterable, List, Optional, Text,
-        Tuple, Union, cast,
+        Tuple, Union,
     )
     from pip._vendor.pkg_resources import Distribution
 
     VersionInfo = Tuple[int, int, int]
-else:
-    # typing's cast() is needed at runtime, but we don't want to import typing.
-    # Thus, we use a dummy no-op version, which we tell mypy to ignore.
-    def cast(type_, value):  # type: ignore
-        return value
 
 
 __all__ = ['rmtree', 'display_path', 'backup_dir',

src/pip/_internal/utils/typing.py

@@ -27,3 +27,12 @@
 """
 
 MYPY_CHECK_RUNNING = False
+
+
+if MYPY_CHECK_RUNNING:
+    from typing import cast
+else:
+    # typing's cast() is needed at runtime, but we don't want to import typing.
+    # Thus, we use a dummy no-op version, which we tell mypy to ignore.
+    def cast(type_, value):  # type: ignore
+        return value