Remove typing.TYPE_CHECKING guards

The typing module has been available since Python 3.5. Guarding the
import has been unnecessary since dropping Python 2.

Some guards remain to either:

- Avoid circular imports
- Importing objects that are also guarded by typing.TYPE_CHECKING
- Avoid mypy_extensions dependency

docs/docs_feedback_sphinxext.py

@@ -3,13 +3,9 @@
 from __future__ import annotations
 
 from itertools import chain
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from typing import Dict, List, Union
-
-    from sphinx.application import Sphinx
+from typing import Dict, List, Union
 
+from sphinx.application import Sphinx
 
 DEFAULT_DOC_LINES_THRESHOLD = 250
 RST_INDENT = 4

src/pip/__init__.py

@@ -1,8 +1,4 @@
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from typing import List, Optional
-
+from typing import List, Optional
 
 __version__ = "21.1.dev0"
 

src/pip/_internal/__init__.py

@@ -1,10 +1,7 @@
-from typing import TYPE_CHECKING
+from typing import List, Optional
 
 import pip._internal.utils.inject_securetransport  # noqa
 
-if TYPE_CHECKING:
-    from typing import List, Optional
-
 
 def main(args=None):
     # type: (Optional[List[str]]) -> int

src/pip/_internal/build_env.py

@@ -8,7 +8,8 @@ import textwrap
 from collections import OrderedDict
 from distutils.sysconfig import get_python_lib
 from sysconfig import get_paths
-from typing import TYPE_CHECKING
+from types import TracebackType
+from typing import TYPE_CHECKING, Iterable, List, Optional, Set, Tuple, Type
 
 from pip._vendor.pkg_resources import Requirement, VersionConflict, WorkingSet
 
@@ -18,9 +19,6 @@ from pip._internal.utils.subprocess import call_subprocess
 from pip._internal.utils.temp_dir import TempDirectory, tempdir_kinds
 
 if TYPE_CHECKING:
-    from types import TracebackType
-    from typing import Iterable, List, Optional, Set, Tuple, Type
-
     from pip._internal.index.package_finder import PackageFinder
 
 logger = logging.getLogger(__name__)

src/pip/_internal/cache.py

@@ -5,24 +5,18 @@ import hashlib
 import json
 import logging
 import os
-from typing import TYPE_CHECKING
+from typing import Any, Dict, List, Optional, Set
 
-from pip._vendor.packaging.tags import interpreter_name, interpreter_version
+from pip._vendor.packaging.tags import Tag, interpreter_name, interpreter_version
 from pip._vendor.packaging.utils import canonicalize_name
 
 from pip._internal.exceptions import InvalidWheelFilename
+from pip._internal.models.format_control import FormatControl
 from pip._internal.models.link import Link
 from pip._internal.models.wheel import Wheel
 from pip._internal.utils.temp_dir import TempDirectory, tempdir_kinds
 from pip._internal.utils.urls import path_to_url
 
-if TYPE_CHECKING:
-    from typing import Any, Dict, List, Optional, Set
-
-    from pip._vendor.packaging.tags import Tag
-
-    from pip._internal.models.format_control import FormatControl
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/cli/autocompletion.py

@@ -5,15 +5,12 @@ import optparse
 import os
 import sys
 from itertools import chain
-from typing import TYPE_CHECKING
+from typing import Any, Iterable, List, Optional
 
 from pip._internal.cli.main_parser import create_main_parser
 from pip._internal.commands import commands_dict, create_command
 from pip._internal.utils.misc import get_installed_distributions
 
-if TYPE_CHECKING:
-    from typing import Any, Iterable, List, Optional
-
 
 def autocomplete():
     # type: () -> None

src/pip/_internal/cli/base_command.py

@@ -6,7 +6,8 @@ import optparse
 import os
 import sys
 import traceback
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import Any, List, Optional, Tuple
 
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.command_context import CommandContextMixIn
@@ -29,17 +30,10 @@ from pip._internal.utils.deprecation import deprecated
 from pip._internal.utils.filesystem import check_path_owner
 from pip._internal.utils.logging import BrokenStdoutLoggingError, setup_logging
 from pip._internal.utils.misc import get_prog, normalize_path
+from pip._internal.utils.temp_dir import TempDirectoryTypeRegistry as TempDirRegistry
 from pip._internal.utils.temp_dir import global_tempdir_manager, tempdir_registry
 from pip._internal.utils.virtualenv import running_under_virtualenv
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Any, List, Optional, Tuple
-
-    from pip._internal.utils.temp_dir import (
-        TempDirectoryTypeRegistry as TempDirRegistry,
-    )
-
 __all__ = ['Command']
 
 logger = logging.getLogger(__name__)

src/pip/_internal/cli/cmdoptions.py

@@ -14,12 +14,13 @@ import os
 import textwrap
 import warnings
 from functools import partial
-from optparse import SUPPRESS_HELP, Option, OptionGroup
+from optparse import SUPPRESS_HELP, Option, OptionGroup, OptionParser, Values
 from textwrap import dedent
-from typing import TYPE_CHECKING
+from typing import Any, Callable, Dict, Optional, Tuple
 
 from pip._vendor.packaging.utils import canonicalize_name
 
+from pip._internal.cli.parser import ConfigOptionParser
 from pip._internal.cli.progress_bars import BAR_TYPES
 from pip._internal.exceptions import CommandError
 from pip._internal.locations import USER_CACHE_DIR, get_src_prefix
@@ -29,12 +30,6 @@ from pip._internal.models.target_python import TargetPython
 from pip._internal.utils.hashes import STRONG_HASHES
 from pip._internal.utils.misc import strtobool
 
-if TYPE_CHECKING:
-    from optparse import OptionParser, Values
-    from typing import Any, Callable, Dict, Optional, Tuple
-
-    from pip._internal.cli.parser import ConfigOptionParser
-
 
 def raise_option_error(parser, option, msg):
     # type: (OptionParser, Option, str) -> None

src/pip/_internal/cli/command_context.py

@@ -1,10 +1,7 @@
 from contextlib import ExitStack, contextmanager
-from typing import TYPE_CHECKING
+from typing import ContextManager, Iterator, TypeVar
 
-if TYPE_CHECKING:
-    from typing import ContextManager, Iterator, TypeVar
-
-    _T = TypeVar('_T', covariant=True)
+_T = TypeVar('_T', covariant=True)
 
 
 class CommandContextMixIn:

src/pip/_internal/cli/main.py

@@ -4,7 +4,7 @@ import locale
 import logging
 import os
 import sys
-from typing import TYPE_CHECKING
+from typing import List, Optional
 
 from pip._internal.cli.autocompletion import autocomplete
 from pip._internal.cli.main_parser import parse_command
@@ -12,9 +12,6 @@ from pip._internal.commands import create_command
 from pip._internal.exceptions import PipError
 from pip._internal.utils import deprecation
 
-if TYPE_CHECKING:
-    from typing import List, Optional
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/cli/main_parser.py

@@ -3,7 +3,7 @@
 
 import os
 import sys
-from typing import TYPE_CHECKING
+from typing import List, Tuple
 
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.parser import ConfigOptionParser, UpdatingDefaultsHelpFormatter
@@ -11,10 +11,6 @@ from pip._internal.commands import commands_dict, get_similar_commands
 from pip._internal.exceptions import CommandError
 from pip._internal.utils.misc import get_pip_version, get_prog
 
-if TYPE_CHECKING:
-    from typing import List, Tuple
-
-
 __all__ = ["create_main_parser", "parse_command"]
 
 

src/pip/_internal/cli/parser.py

@@ -9,15 +9,12 @@ import shutil
 import sys
 import textwrap
 from contextlib import suppress
-from typing import TYPE_CHECKING
+from typing import Any
 
 from pip._internal.cli.status_codes import UNKNOWN_ERROR
 from pip._internal.configuration import Configuration, ConfigurationError
 from pip._internal.utils.misc import redact_auth_from_url, strtobool
 
-if TYPE_CHECKING:
-    from typing import Any
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/cli/progress_bars.py

@@ -1,7 +1,7 @@
 import itertools
 import sys
 from signal import SIGINT, default_int_handler, signal
-from typing import TYPE_CHECKING
+from typing import Any, Dict, List
 
 from pip._vendor.progress.bar import Bar, FillingCirclesBar, IncrementalBar
 from pip._vendor.progress.spinner import Spinner
@@ -10,9 +10,6 @@ from pip._internal.utils.compat import WINDOWS
 from pip._internal.utils.logging import get_indentation
 from pip._internal.utils.misc import format_size
 
-if TYPE_CHECKING:
-    from typing import Any, Dict, List
-
 try:
     from pip._vendor import colorama
 # Lots of different errors can come from this, including SystemError and

src/pip/_internal/cli/req_command.py

@@ -8,8 +8,10 @@ PackageFinder machinery and all its vendored dependencies, etc.
 import logging
 import os
 from functools import partial
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import Any, List, Optional, Tuple
 
+from pip._internal.cache import WheelCache
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.base_command import Command
 from pip._internal.cli.command_context import CommandContextMixIn
@@ -17,6 +19,7 @@ from pip._internal.exceptions import CommandError, PreviousBuildDirError
 from pip._internal.index.collector import LinkCollector
 from pip._internal.index.package_finder import PackageFinder
 from pip._internal.models.selection_prefs import SelectionPreferences
+from pip._internal.models.target_python import TargetPython
 from pip._internal.network.session import PipSession
 from pip._internal.operations.prepare import RequirementPreparer
 from pip._internal.req.constructors import (
@@ -26,20 +29,15 @@ from pip._internal.req.constructors import (
     install_req_from_req_string,
 )
 from pip._internal.req.req_file import parse_requirements
+from pip._internal.req.req_install import InstallRequirement
+from pip._internal.req.req_tracker import RequirementTracker
+from pip._internal.resolution.base import BaseResolver
 from pip._internal.self_outdated_check import pip_self_version_check
-from pip._internal.utils.temp_dir import tempdir_kinds
-
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Any, List, Optional, Tuple
-
-    from pip._internal.cache import WheelCache
-    from pip._internal.models.target_python import TargetPython
-    from pip._internal.req.req_install import InstallRequirement
-    from pip._internal.req.req_tracker import RequirementTracker
-    from pip._internal.resolution.base import BaseResolver
-    from pip._internal.utils.temp_dir import TempDirectory, TempDirectoryTypeRegistry
-
+from pip._internal.utils.temp_dir import (
+    TempDirectory,
+    TempDirectoryTypeRegistry,
+    tempdir_kinds,
+)
 
 logger = logging.getLogger(__name__)
 

src/pip/_internal/cli/spinners.py

@@ -3,16 +3,13 @@ import itertools
 import logging
 import sys
 import time
-from typing import TYPE_CHECKING
+from typing import IO, Iterator
 
 from pip._vendor.progress import HIDE_CURSOR, SHOW_CURSOR
 
 from pip._internal.utils.compat import WINDOWS
 from pip._internal.utils.logging import get_indentation
 
-if TYPE_CHECKING:
-    from typing import IO, Iterator
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/commands/__init__.py

@@ -4,13 +4,9 @@ Package containing all pip commands
 
 import importlib
 from collections import OrderedDict, namedtuple
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from typing import Any, Optional
-
-    from pip._internal.cli.base_command import Command
+from typing import Any, Optional
 
+from pip._internal.cli.base_command import Command
 
 CommandInfo = namedtuple('CommandInfo', 'module_path, class_name, summary')
 

src/pip/_internal/commands/cache.py

@@ -1,18 +1,14 @@
 import logging
 import os
 import textwrap
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import Any, List
 
 import pip._internal.utils.filesystem as filesystem
 from pip._internal.cli.base_command import Command
 from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.exceptions import CommandError, PipError
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Any, List
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/commands/check.py

@@ -1,5 +1,6 @@
 import logging
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import Any, List
 
 from pip._internal.cli.base_command import Command
 from pip._internal.cli.status_codes import ERROR, SUCCESS
@@ -11,10 +12,6 @@ from pip._internal.utils.misc import write_output
 
 logger = logging.getLogger(__name__)
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Any, List
-
 
 class CheckCommand(Command):
     """Verify installed packages have compatible dependencies."""

src/pip/_internal/commands/completion.py

@@ -1,15 +1,12 @@
 import sys
 import textwrap
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import List
 
 from pip._internal.cli.base_command import Command
 from pip._internal.cli.status_codes import SUCCESS
 from pip._internal.utils.misc import get_prog
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import List
-
 BASE_COMPLETION = """
 # pip {shell} completion start{script}# pip {shell} completion end
 """

src/pip/_internal/commands/configuration.py

@@ -1,21 +1,21 @@
 import logging
 import os
 import subprocess
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import Any, List, Optional
 
 from pip._internal.cli.base_command import Command
 from pip._internal.cli.status_codes import ERROR, SUCCESS
-from pip._internal.configuration import Configuration, get_configuration_files, kinds
+from pip._internal.configuration import (
+    Configuration,
+    Kind,
+    get_configuration_files,
+    kinds,
+)
 from pip._internal.exceptions import PipError
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.misc import get_prog, write_output
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Any, List, Optional
-
-    from pip._internal.configuration import Kind
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/commands/debug.py

@@ -2,7 +2,9 @@ import locale
 import logging
 import os
 import sys
-from typing import TYPE_CHECKING
+from optparse import Values
+from types import ModuleType
+from typing import Dict, List, Optional
 
 import pip._vendor
 from pip._vendor.certifi import where
@@ -13,17 +15,11 @@ from pip._internal.cli import cmdoptions
 from pip._internal.cli.base_command import Command
 from pip._internal.cli.cmdoptions import make_target_python
 from pip._internal.cli.status_codes import SUCCESS
+from pip._internal.configuration import Configuration
 from pip._internal.metadata import get_environment
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.misc import get_pip_version
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from types import ModuleType
-    from typing import Dict, List, Optional
-
-    from pip._internal.configuration import Configuration
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/commands/download.py

@@ -1,6 +1,7 @@
 import logging
 import os
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import List
 
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.cmdoptions import make_target_python
@@ -10,10 +11,6 @@ from pip._internal.req.req_tracker import get_requirement_tracker
 from pip._internal.utils.misc import ensure_dir, normalize_path, write_output
 from pip._internal.utils.temp_dir import TempDirectory
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import List
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/commands/freeze.py

@@ -1,5 +1,6 @@
 import sys
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import List
 
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.base_command import Command
@@ -10,10 +11,6 @@ from pip._internal.utils.deprecation import deprecated
 
 DEV_PKGS = {'pip', 'setuptools', 'distribute', 'wheel'}
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import List
-
 
 class FreezeCommand(Command):
     """

src/pip/_internal/commands/hash.py

@@ -1,17 +1,14 @@
 import hashlib
 import logging
 import sys
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import List
 
 from pip._internal.cli.base_command import Command
 from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.utils.hashes import FAVORITE_HASH, STRONG_HASHES
 from pip._internal.utils.misc import read_chunks, write_output
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import List
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/commands/help.py

@@ -1,13 +1,10 @@
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import List
 
 from pip._internal.cli.base_command import Command
 from pip._internal.cli.status_codes import SUCCESS
 from pip._internal.exceptions import CommandError
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import List
-
 
 class HelpCommand(Command):
     """Show help for commands"""

src/pip/_internal/commands/install.py

@@ -4,8 +4,8 @@ import operator
 import os
 import shutil
 import site
-from optparse import SUPPRESS_HELP
-from typing import TYPE_CHECKING
+from optparse import SUPPRESS_HELP, Values
+from typing import Iterable, List, Optional
 
 from pip._vendor.packaging.utils import canonicalize_name
 
@@ -17,8 +17,10 @@ from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.exceptions import CommandError, InstallationError
 from pip._internal.locations import distutils_scheme
 from pip._internal.metadata import get_environment
-from pip._internal.operations.check import check_install_conflicts
+from pip._internal.models.format_control import FormatControl
+from pip._internal.operations.check import ConflictDetails, check_install_conflicts
 from pip._internal.req import install_given_reqs
+from pip._internal.req.req_install import InstallRequirement
 from pip._internal.req.req_tracker import get_requirement_tracker
 from pip._internal.utils.distutils_args import parse_distutils_args
 from pip._internal.utils.filesystem import test_writable_dir
@@ -30,17 +32,11 @@ from pip._internal.utils.misc import (
 )
 from pip._internal.utils.temp_dir import TempDirectory
 from pip._internal.utils.virtualenv import virtualenv_no_global
-from pip._internal.wheel_builder import build, should_build_for_install_command
-
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Iterable, List, Optional
-
-    from pip._internal.models.format_control import FormatControl
-    from pip._internal.operations.check import ConflictDetails
-    from pip._internal.req.req_install import InstallRequirement
-    from pip._internal.wheel_builder import BinaryAllowedPredicate
-
+from pip._internal.wheel_builder import (
+    BinaryAllowedPredicate,
+    build,
+    should_build_for_install_command,
+)
 
 logger = logging.getLogger(__name__)
 

src/pip/_internal/commands/list.py

@@ -1,6 +1,9 @@
 import json
 import logging
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import Iterator, List, Set, Tuple
+
+from pip._vendor.pkg_resources import Distribution
 
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.req_command import IndexGroupCommand
@@ -9,6 +12,7 @@ from pip._internal.exceptions import CommandError
 from pip._internal.index.collector import LinkCollector
 from pip._internal.index.package_finder import PackageFinder
 from pip._internal.models.selection_prefs import SelectionPreferences
+from pip._internal.network.session import PipSession
 from pip._internal.utils.compat import stdlib_pkgs
 from pip._internal.utils.misc import (
     dist_is_editable,
@@ -19,14 +23,6 @@ from pip._internal.utils.misc import (
 from pip._internal.utils.packaging import get_installer
 from pip._internal.utils.parallel import map_multithread
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Iterator, List, Set, Tuple
-
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.network.session import PipSession
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/commands/search.py

@@ -3,7 +3,8 @@ import shutil
 import sys
 import textwrap
 from collections import OrderedDict
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import TYPE_CHECKING, Dict, List, Optional
 
 from pip._vendor.packaging.version import parse as parse_version
 
@@ -22,10 +23,8 @@ from pip._internal.utils.logging import indent_log
 from pip._internal.utils.misc import write_output
 
 if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Dict, List, Optional
+    from typing import TypedDict
 
-    from typing_extensions import TypedDict
     TransformedHit = TypedDict(
         'TransformedHit',
         {'name': str, 'summary': str, 'versions': List[str]},

src/pip/_internal/commands/show.py

@@ -1,7 +1,8 @@
 import logging
 import os
 from email.parser import FeedParser
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import Dict, Iterator, List
 
 from pip._vendor import pkg_resources
 from pip._vendor.packaging.utils import canonicalize_name
@@ -10,10 +11,6 @@ from pip._internal.cli.base_command import Command
 from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.utils.misc import write_output
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import Dict, Iterator, List
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/commands/uninstall.py

@@ -1,4 +1,5 @@
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import List
 
 from pip._vendor.packaging.utils import canonicalize_name
 
@@ -13,10 +14,6 @@ from pip._internal.req.constructors import (
 )
 from pip._internal.utils.misc import protect_pip_from_modification_on_windows
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import List
-
 
 class UninstallCommand(Command, SessionCommandMixin):
     """

src/pip/_internal/commands/wheel.py

@@ -1,24 +1,20 @@
 import logging
 import os
 import shutil
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import List
 
 from pip._internal.cache import WheelCache
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.req_command import RequirementCommand, with_cleanup
 from pip._internal.cli.status_codes import SUCCESS
 from pip._internal.exceptions import CommandError
+from pip._internal.req.req_install import InstallRequirement
 from pip._internal.req.req_tracker import get_requirement_tracker
 from pip._internal.utils.misc import ensure_dir, normalize_path
 from pip._internal.utils.temp_dir import TempDirectory
 from pip._internal.wheel_builder import build, should_build_for_wheel_command
 
-if TYPE_CHECKING:
-    from optparse import Values
-    from typing import List
-
-    from pip._internal.req.req_install import InstallRequirement
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/configuration.py

@@ -16,7 +16,7 @@ import locale
 import logging
 import os
 import sys
-from typing import TYPE_CHECKING
+from typing import Any, Dict, Iterable, List, NewType, Optional, Tuple
 
 from pip._internal.exceptions import (
     ConfigurationError,
@@ -26,11 +26,8 @@ from pip._internal.utils import appdirs
 from pip._internal.utils.compat import WINDOWS
 from pip._internal.utils.misc import ensure_dir, enum
 
-if TYPE_CHECKING:
-    from typing import Any, Dict, Iterable, List, NewType, Optional, Tuple
-
-    RawConfigParser = configparser.RawConfigParser  # Shorthand
-    Kind = NewType("Kind", str)
+RawConfigParser = configparser.RawConfigParser  # Shorthand
+Kind = NewType("Kind", str)
 
 CONFIG_BASENAME = 'pip.ini' if WINDOWS else 'pip.conf'
 ENV_NAMES_IGNORED = "version", "help"

src/pip/_internal/distributions/__init__.py

@@ -1,11 +1,7 @@
-from typing import TYPE_CHECKING
-
+from pip._internal.distributions.base import AbstractDistribution
 from pip._internal.distributions.sdist import SourceDistribution
 from pip._internal.distributions.wheel import WheelDistribution
-
-if TYPE_CHECKING:
-    from pip._internal.distributions.base import AbstractDistribution
-    from pip._internal.req.req_install import InstallRequirement
+from pip._internal.req.req_install import InstallRequirement
 
 
 def make_distribution_for_install_requirement(install_req):

src/pip/_internal/distributions/base.py

@@ -1,13 +1,10 @@
 import abc
-from typing import TYPE_CHECKING
+from typing import Optional
 
-if TYPE_CHECKING:
-    from typing import Optional
+from pip._vendor.pkg_resources import Distribution
 
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.index.package_finder import PackageFinder
-    from pip._internal.req import InstallRequirement
+from pip._internal.index.package_finder import PackageFinder
+from pip._internal.req import InstallRequirement
 
 
 class AbstractDistribution(metaclass=abc.ABCMeta):

src/pip/_internal/distributions/installed.py

@@ -1,13 +1,9 @@
-from typing import TYPE_CHECKING
+from typing import Optional
+
+from pip._vendor.pkg_resources import Distribution
 
 from pip._internal.distributions.base import AbstractDistribution
-
-if TYPE_CHECKING:
-    from typing import Optional
-
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.index.package_finder import PackageFinder
+from pip._internal.index.package_finder import PackageFinder
 
 
 class InstalledDistribution(AbstractDistribution):

src/pip/_internal/distributions/sdist.py

@@ -1,19 +1,14 @@
 import logging
-from typing import TYPE_CHECKING
+from typing import Set, Tuple
+
+from pip._vendor.pkg_resources import Distribution
 
 from pip._internal.build_env import BuildEnvironment
 from pip._internal.distributions.base import AbstractDistribution
 from pip._internal.exceptions import InstallationError
+from pip._internal.index.package_finder import PackageFinder
 from pip._internal.utils.subprocess import runner_with_spinner_message
 
-if TYPE_CHECKING:
-    from typing import Set, Tuple
-
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.index.package_finder import PackageFinder
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/distributions/wheel.py

@@ -1,14 +1,11 @@
-from typing import TYPE_CHECKING
 from zipfile import ZipFile
 
+from pip._vendor.pkg_resources import Distribution
+
 from pip._internal.distributions.base import AbstractDistribution
+from pip._internal.index.package_finder import PackageFinder
 from pip._internal.utils.wheel import pkg_resources_distribution_for_wheel
 
-if TYPE_CHECKING:
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.index.package_finder import PackageFinder
-
 
 class WheelDistribution(AbstractDistribution):
     """Represents a wheel distribution.

src/pip/_internal/exceptions.py

@@ -1,15 +1,14 @@
 """Exceptions used throughout package"""
 
+import configparser
 from itertools import chain, groupby, repeat
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Dict, List, Optional
+
+from pip._vendor.pkg_resources import Distribution
+from pip._vendor.requests.models import Request, Response
 
 if TYPE_CHECKING:
-    import configparser
     from hashlib import _Hash
-    from typing import Dict, List, Optional
-
-    from pip._vendor.pkg_resources import Distribution
-    from pip._vendor.requests.models import Request, Response
 
     from pip._internal.req.req_install import InstallRequirement
 

src/pip/_internal/index/collector.py

@@ -11,46 +11,40 @@ import os
 import re
 import urllib.parse
 import urllib.request
+import xml.etree.ElementTree
 from collections import OrderedDict
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import (
+    Callable,
+    Iterable,
+    List,
+    MutableMapping,
+    Optional,
+    Sequence,
+    Tuple,
+    Union,
+)
 
 from pip._vendor import html5lib, requests
 from pip._vendor.distlib.compat import unescape
+from pip._vendor.requests import Response
 from pip._vendor.requests.exceptions import RetryError, SSLError
 
 from pip._internal.exceptions import NetworkConnectionError
 from pip._internal.models.link import Link
 from pip._internal.models.search_scope import SearchScope
+from pip._internal.network.session import PipSession
 from pip._internal.network.utils import raise_for_status
 from pip._internal.utils.filetypes import is_archive_file
 from pip._internal.utils.misc import pairwise, redact_auth_from_url
 from pip._internal.utils.urls import path_to_url, url_to_path
 from pip._internal.vcs import is_url, vcs
 
-if TYPE_CHECKING:
-    import xml.etree.ElementTree
-    from optparse import Values
-    from typing import (
-        Callable,
-        Iterable,
-        List,
-        MutableMapping,
-        Optional,
-        Sequence,
-        Tuple,
-        Union,
-    )
-
-    from pip._vendor.requests import Response
-
-    from pip._internal.network.session import PipSession
-
-    HTMLElement = xml.etree.ElementTree.Element
-    ResponseHeaders = MutableMapping[str, str]
-
-
 logger = logging.getLogger(__name__)
 
+HTMLElement = xml.etree.ElementTree.Element
+ResponseHeaders = MutableMapping[str, str]
+
 
 def _match_vcs_scheme(url):
     # type: (str) -> Optional[str]

src/pip/_internal/index/package_finder.py

@@ -6,10 +6,12 @@
 import functools
 import logging
 import re
-from typing import TYPE_CHECKING
+from typing import FrozenSet, Iterable, List, Optional, Set, Tuple, Union
 
 from pip._vendor.packaging import specifiers
+from pip._vendor.packaging.tags import Tag
 from pip._vendor.packaging.utils import canonicalize_name
+from pip._vendor.packaging.version import _BaseVersion
 from pip._vendor.packaging.version import parse as parse_version
 
 from pip._internal.exceptions import (
@@ -18,42 +20,33 @@ from pip._internal.exceptions import (
     InvalidWheelFilename,
     UnsupportedWheel,
 )
-from pip._internal.index.collector import parse_links
+from pip._internal.index.collector import LinkCollector, parse_links
 from pip._internal.models.candidate import InstallationCandidate
 from pip._internal.models.format_control import FormatControl
 from pip._internal.models.link import Link
+from pip._internal.models.search_scope import SearchScope
 from pip._internal.models.selection_prefs import SelectionPreferences
 from pip._internal.models.target_python import TargetPython
 from pip._internal.models.wheel import Wheel
+from pip._internal.req import InstallRequirement
 from pip._internal.utils.filetypes import WHEEL_EXTENSION
+from pip._internal.utils.hashes import Hashes
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.misc import build_netloc
 from pip._internal.utils.packaging import check_requires_python
 from pip._internal.utils.unpacking import SUPPORTED_EXTENSIONS
 from pip._internal.utils.urls import url_to_path
 
-if TYPE_CHECKING:
-    from typing import FrozenSet, Iterable, List, Optional, Set, Tuple, Union
-
-    from pip._vendor.packaging.tags import Tag
-    from pip._vendor.packaging.version import _BaseVersion
-
-    from pip._internal.index.collector import LinkCollector
-    from pip._internal.models.search_scope import SearchScope
-    from pip._internal.req import InstallRequirement
-    from pip._internal.utils.hashes import Hashes
-
-    BuildTag = Union[Tuple[()], Tuple[int, str]]
-    CandidateSortingKey = (
-        Tuple[int, int, int, _BaseVersion, BuildTag, Optional[int]]
-    )
-
-
 __all__ = ['FormatControl', 'BestCandidateResult', 'PackageFinder']
 
 
 logger = logging.getLogger(__name__)
 
+BuildTag = Union[Tuple[()], Tuple[int, str]]
+CandidateSortingKey = (
+    Tuple[int, int, int, _BaseVersion, BuildTag, Optional[int]]
+)
+
 
 def _check_link_requires_python(
     link,  # type: Link

src/pip/_internal/locations.py

@@ -8,20 +8,16 @@ import os.path
 import site
 import sys
 import sysconfig
+from distutils.cmd import Command as DistutilsCommand
 from distutils.command.install import SCHEME_KEYS
 from distutils.command.install import install as distutils_install_command
-from typing import TYPE_CHECKING, cast
+from typing import Dict, List, Optional, Union, cast
 
 from pip._internal.models.scheme import Scheme
 from pip._internal.utils import appdirs
 from pip._internal.utils.compat import WINDOWS
 from pip._internal.utils.virtualenv import running_under_virtualenv
 
-if TYPE_CHECKING:
-    from distutils.cmd import Command as DistutilsCommand
-    from typing import Dict, List, Optional, Union
-
-
 # Application Directories
 USER_CACHE_DIR = appdirs.user_cache_dir("pip")
 

src/pip/_internal/main.py

@@ -1,7 +1,4 @@
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from typing import List, Optional
+from typing import List, Optional
 
 
 def main(args=None):

src/pip/_internal/metadata/__init__.py

@@ -1,9 +1,6 @@
-from typing import TYPE_CHECKING
+from typing import List, Optional
 
-if TYPE_CHECKING:
-    from typing import List, Optional
-
-    from .base import BaseDistribution, BaseEnvironment
+from .base import BaseDistribution, BaseEnvironment
 
 
 def get_default_environment():

src/pip/_internal/metadata/base.py

@@ -1,12 +1,9 @@
-from typing import TYPE_CHECKING
+from typing import Container, Iterator, List, Optional
+
+from pip._vendor.packaging.version import _BaseVersion
 
 from pip._internal.utils.misc import stdlib_pkgs  # TODO: Move definition here.
 
-if TYPE_CHECKING:
-    from typing import Container, Iterator, List, Optional
-
-    from pip._vendor.packaging.version import _BaseVersion
-
 
 class BaseDistribution:
     @property

src/pip/_internal/metadata/pkg_resources.py

@@ -1,8 +1,9 @@
 import zipfile
-from typing import TYPE_CHECKING
+from typing import Iterator, List, Optional
 
 from pip._vendor import pkg_resources
 from pip._vendor.packaging.utils import canonicalize_name
+from pip._vendor.packaging.version import _BaseVersion
 
 from pip._internal.utils import misc  # TODO: Move definition here.
 from pip._internal.utils.packaging import get_installer
@@ -10,11 +11,6 @@ from pip._internal.utils.wheel import pkg_resources_distribution_for_wheel
 
 from .base import BaseDistribution, BaseEnvironment
 
-if TYPE_CHECKING:
-    from typing import Iterator, List, Optional
-
-    from pip._vendor.packaging.version import _BaseVersion
-
 
 class Distribution(BaseDistribution):
     def __init__(self, dist):

src/pip/_internal/models/candidate.py

@@ -1,14 +1,9 @@
-from typing import TYPE_CHECKING
-
+from pip._vendor.packaging.version import _BaseVersion
 from pip._vendor.packaging.version import parse as parse_version
 
+from pip._internal.models.link import Link
 from pip._internal.utils.models import KeyBasedCompareMixin
 
-if TYPE_CHECKING:
-    from pip._vendor.packaging.version import _BaseVersion
-
-    from pip._internal.models.link import Link
-
 
 class InstallationCandidate(KeyBasedCompareMixin):
     """Represents a potential "candidate" for installation.

src/pip/_internal/models/direct_url.py

@@ -2,16 +2,7 @@
 import json
 import re
 import urllib.parse
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from typing import Any, Dict, Iterable, Optional, Type, TypeVar, Union
-
-    T = TypeVar("T")
-
-
-DIRECT_URL_METADATA_NAME = "direct_url.json"
-ENV_VAR_RE = re.compile(r"^\$\{[A-Za-z0-9-_]+\}(:\$\{[A-Za-z0-9-_]+\})?$")
+from typing import Any, Dict, Iterable, Optional, Type, TypeVar, Union
 
 __all__ = [
     "DirectUrl",
@@ -21,6 +12,11 @@ __all__ = [
     "VcsInfo",
 ]
 
+T = TypeVar("T")
+
+DIRECT_URL_METADATA_NAME = "direct_url.json"
+ENV_VAR_RE = re.compile(r"^\$\{[A-Za-z0-9-_]+\}(:\$\{[A-Za-z0-9-_]+\})?$")
+
 
 class DirectUrlValidationError(Exception):
     pass
@@ -155,8 +151,7 @@ class DirInfo:
         return _filter_none(editable=self.editable or None)
 
 
-if TYPE_CHECKING:
-    InfoType = Union[ArchiveInfo, DirInfo, VcsInfo]
+InfoType = Union[ArchiveInfo, DirInfo, VcsInfo]
 
 
 class DirectUrl:

src/pip/_internal/models/format_control.py

@@ -1,12 +1,9 @@
-from typing import TYPE_CHECKING
+from typing import FrozenSet, Optional, Set
 
 from pip._vendor.packaging.utils import canonicalize_name
 
 from pip._internal.exceptions import CommandError
 
-if TYPE_CHECKING:
-    from typing import FrozenSet, Optional, Set
-
 
 class FormatControl:
     """Helper for managing formats from which a package can be installed.

src/pip/_internal/models/link.py

@@ -2,9 +2,10 @@ import os
 import posixpath
 import re
 import urllib.parse
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Optional, Tuple, Union
 
 from pip._internal.utils.filetypes import WHEEL_EXTENSION
+from pip._internal.utils.hashes import Hashes
 from pip._internal.utils.misc import (
     redact_auth_from_url,
     split_auth_from_netloc,
@@ -14,10 +15,7 @@ from pip._internal.utils.models import KeyBasedCompareMixin
 from pip._internal.utils.urls import path_to_url, url_to_path
 
 if TYPE_CHECKING:
-    from typing import Optional, Tuple, Union
-
     from pip._internal.index.collector import HTMLPage
-    from pip._internal.utils.hashes import Hashes
 
 
 class Link(KeyBasedCompareMixin):

src/pip/_internal/models/search_scope.py

@@ -3,7 +3,7 @@ import logging
 import os
 import posixpath
 import urllib.parse
-from typing import TYPE_CHECKING
+from typing import List
 
 from pip._vendor.packaging.utils import canonicalize_name
 
@@ -11,10 +11,6 @@ from pip._internal.models.index import PyPI
 from pip._internal.utils.compat import has_tls
 from pip._internal.utils.misc import normalize_path, redact_auth_from_url
 
-if TYPE_CHECKING:
-    from typing import List
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/models/selection_prefs.py

@@ -1,9 +1,6 @@
-from typing import TYPE_CHECKING
+from typing import Optional
 
-if TYPE_CHECKING:
-    from typing import Optional
-
-    from pip._internal.models.format_control import FormatControl
+from pip._internal.models.format_control import FormatControl
 
 
 class SelectionPreferences:

src/pip/_internal/models/target_python.py

@@ -1,14 +1,11 @@
 import sys
-from typing import TYPE_CHECKING
+from typing import List, Optional, Tuple
+
+from pip._vendor.packaging.tags import Tag
 
 from pip._internal.utils.compatibility_tags import get_supported, version_info_to_nodot
 from pip._internal.utils.misc import normalize_version_info
 
-if TYPE_CHECKING:
-    from typing import List, Optional, Tuple
-
-    from pip._vendor.packaging.tags import Tag
-
 
 class TargetPython:
 

src/pip/_internal/models/wheel.py

@@ -2,15 +2,12 @@
 name that have meaning.
 """
 import re
-from typing import TYPE_CHECKING
+from typing import List
 
 from pip._vendor.packaging.tags import Tag
 
 from pip._internal.exceptions import InvalidWheelFilename
 
-if TYPE_CHECKING:
-    from typing import List
-
 
 class Wheel:
     """A wheel file"""

src/pip/_internal/network/auth.py

@@ -6,9 +6,10 @@ providing credentials in the context of network requests.
 
 import logging
 import urllib.parse
-from typing import TYPE_CHECKING
+from typing import Any, Dict, List, Optional, Tuple
 
 from pip._vendor.requests.auth import AuthBase, HTTPBasicAuth
+from pip._vendor.requests.models import Request, Response
 from pip._vendor.requests.utils import get_netrc_auth
 
 from pip._internal.utils.misc import (
@@ -18,18 +19,12 @@ from pip._internal.utils.misc import (
     remove_auth_from_url,
     split_auth_netloc_from_url,
 )
-
-if TYPE_CHECKING:
-    from typing import Any, Dict, List, Optional, Tuple
-
-    from pip._vendor.requests.models import Request, Response
-
-    from pip._internal.vcs.versioncontrol import AuthInfo
-
-    Credentials = Tuple[str, str, str]
+from pip._internal.vcs.versioncontrol import AuthInfo
 
 logger = logging.getLogger(__name__)
 
+Credentials = Tuple[str, str, str]
+
 try:
     import keyring
 except ImportError:

src/pip/_internal/network/cache.py

@@ -3,7 +3,7 @@
 
 import os
 from contextlib import contextmanager
-from typing import TYPE_CHECKING
+from typing import Iterator, Optional
 
 from pip._vendor.cachecontrol.cache import BaseCache
 from pip._vendor.cachecontrol.caches import FileCache
@@ -12,9 +12,6 @@ from pip._vendor.requests.models import Response
 from pip._internal.utils.filesystem import adjacent_tmp_file, replace
 from pip._internal.utils.misc import ensure_dir
 
-if TYPE_CHECKING:
-    from typing import Iterator, Optional
-
 
 def is_from_cache(response):
     # type: (Response) -> bool

src/pip/_internal/network/download.py

@@ -4,25 +4,19 @@ import cgi
 import logging
 import mimetypes
 import os
-from typing import TYPE_CHECKING
+from typing import Iterable, Optional, Tuple
 
-from pip._vendor.requests.models import CONTENT_CHUNK_SIZE
+from pip._vendor.requests.models import CONTENT_CHUNK_SIZE, Response
 
 from pip._internal.cli.progress_bars import DownloadProgressProvider
 from pip._internal.exceptions import NetworkConnectionError
 from pip._internal.models.index import PyPI
+from pip._internal.models.link import Link
 from pip._internal.network.cache import is_from_cache
+from pip._internal.network.session import PipSession
 from pip._internal.network.utils import HEADERS, raise_for_status, response_chunks
 from pip._internal.utils.misc import format_size, redact_auth_from_url, splitext
 
-if TYPE_CHECKING:
-    from typing import Iterable, Optional, Tuple
-
-    from pip._vendor.requests.models import Response
-
-    from pip._internal.models.link import Link
-    from pip._internal.network.session import PipSession
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/network/lazy_wheel.py

@@ -5,22 +5,16 @@ __all__ = ['HTTPRangeRequestUnsupported', 'dist_from_wheel_url']
 from bisect import bisect_left, bisect_right
 from contextlib import contextmanager
 from tempfile import NamedTemporaryFile
-from typing import TYPE_CHECKING
+from typing import Any, Dict, Iterator, List, Optional, Tuple
 from zipfile import BadZipfile, ZipFile
 
-from pip._vendor.requests.models import CONTENT_CHUNK_SIZE
+from pip._vendor.pkg_resources import Distribution
+from pip._vendor.requests.models import CONTENT_CHUNK_SIZE, Response
 
+from pip._internal.network.session import PipSession
 from pip._internal.network.utils import HEADERS, raise_for_status, response_chunks
 from pip._internal.utils.wheel import pkg_resources_distribution_for_wheel
 
-if TYPE_CHECKING:
-    from typing import Any, Dict, Iterator, List, Optional, Tuple
-
-    from pip._vendor.pkg_resources import Distribution
-    from pip._vendor.requests.models import Response
-
-    from pip._internal.network.session import PipSession
-
 
 class HTTPRangeRequestUnsupported(Exception):
     pass

src/pip/_internal/network/session.py

@@ -15,7 +15,7 @@ import platform
 import sys
 import urllib.parse
 import warnings
-from typing import TYPE_CHECKING
+from typing import Any, Iterator, List, Optional, Sequence, Tuple, Union
 
 from pip._vendor import requests, urllib3
 from pip._vendor.cachecontrol import CacheControlAdapter
@@ -26,6 +26,7 @@ from pip._vendor.urllib3.exceptions import InsecureRequestWarning
 
 from pip import __version__
 from pip._internal.metadata import get_default_environment
+from pip._internal.models.link import Link
 from pip._internal.network.auth import MultiDomainBasicAuth
 from pip._internal.network.cache import SafeFileCache
 
@@ -35,16 +36,10 @@ from pip._internal.utils.glibc import libc_ver
 from pip._internal.utils.misc import build_url_from_netloc, parse_netloc
 from pip._internal.utils.urls import url_to_path
 
-if TYPE_CHECKING:
-    from typing import Any, Iterator, List, Optional, Sequence, Tuple, Union
-
-    from pip._internal.models.link import Link
-
-    SecureOrigin = Tuple[str, str, Optional[Union[int, str]]]
-
-
 logger = logging.getLogger(__name__)
 
+SecureOrigin = Tuple[str, str, Optional[Union[int, str]]]
+
 
 # Ignore warning raised when using --trusted-host.
 warnings.filterwarnings("ignore", category=InsecureRequestWarning)

src/pip/_internal/network/utils.py

@@ -1,12 +1,9 @@
-from typing import TYPE_CHECKING
+from typing import Dict, Iterator
 
 from pip._vendor.requests.models import CONTENT_CHUNK_SIZE, Response
 
 from pip._internal.exceptions import NetworkConnectionError
 
-if TYPE_CHECKING:
-    from typing import Dict, Iterator
-
 # The following comments and HTTP headers were originally added by
 # Donald Stufft in git commit 22c562429a61bb77172039e480873fb239dd8c03.
 #

src/pip/_internal/network/xmlrpc.py

@@ -3,21 +3,16 @@
 
 import logging
 import urllib.parse
-from typing import TYPE_CHECKING
+from typing import Dict
 
 # NOTE: XMLRPC Client is not annotated in typeshed as on 2017-07-17, which is
 #       why we ignore the type on this import
 from pip._vendor.six.moves import xmlrpc_client  # type: ignore
 
 from pip._internal.exceptions import NetworkConnectionError
+from pip._internal.network.session import PipSession
 from pip._internal.network.utils import raise_for_status
 
-if TYPE_CHECKING:
-    from typing import Dict
-
-    from pip._internal.network.session import PipSession
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/operations/build/metadata.py

@@ -2,16 +2,13 @@
 """
 
 import os
-from typing import TYPE_CHECKING
 
+from pip._vendor.pep517.wrappers import Pep517HookCaller
+
+from pip._internal.build_env import BuildEnvironment
 from pip._internal.utils.subprocess import runner_with_spinner_message
 from pip._internal.utils.temp_dir import TempDirectory
 
-if TYPE_CHECKING:
-    from pip._vendor.pep517.wrappers import Pep517HookCaller
-
-    from pip._internal.build_env import BuildEnvironment
-
 
 def generate_metadata(build_env, backend):
     # type: (BuildEnvironment, Pep517HookCaller) -> str

src/pip/_internal/operations/build/metadata_legacy.py

@@ -3,16 +3,13 @@
 
 import logging
 import os
-from typing import TYPE_CHECKING
 
+from pip._internal.build_env import BuildEnvironment
 from pip._internal.exceptions import InstallationError
 from pip._internal.utils.setuptools_build import make_setuptools_egg_info_args
 from pip._internal.utils.subprocess import call_subprocess
 from pip._internal.utils.temp_dir import TempDirectory
 
-if TYPE_CHECKING:
-    from pip._internal.build_env import BuildEnvironment
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/operations/build/wheel.py

@@ -1,14 +1,11 @@
 import logging
 import os
-from typing import TYPE_CHECKING
+from typing import List, Optional
+
+from pip._vendor.pep517.wrappers import Pep517HookCaller
 
 from pip._internal.utils.subprocess import runner_with_spinner_message
 
-if TYPE_CHECKING:
-    from typing import List, Optional
-
-    from pip._vendor.pep517.wrappers import Pep517HookCaller
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/operations/build/wheel_legacy.py

@@ -1,6 +1,6 @@
 import logging
 import os.path
-from typing import TYPE_CHECKING
+from typing import List, Optional
 
 from pip._internal.cli.spinners import open_spinner
 from pip._internal.utils.setuptools_build import make_setuptools_bdist_wheel_args
@@ -10,9 +10,6 @@ from pip._internal.utils.subprocess import (
     format_command_args,
 )
 
-if TYPE_CHECKING:
-    from typing import List, Optional
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/operations/check.py

@@ -3,30 +3,26 @@
 
 import logging
 from collections import namedtuple
-from typing import TYPE_CHECKING
+from typing import Any, Callable, Dict, List, Optional, Set, Tuple
 
 from pip._vendor.packaging.utils import canonicalize_name
 from pip._vendor.pkg_resources import RequirementParseError
 
 from pip._internal.distributions import make_distribution_for_install_requirement
+from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.misc import get_installed_distributions
 
 logger = logging.getLogger(__name__)
 
-if TYPE_CHECKING:
-    from typing import Any, Callable, Dict, List, Optional, Set, Tuple
+# Shorthands
+PackageSet = Dict[str, 'PackageDetails']
+Missing = Tuple[str, Any]
+Conflicting = Tuple[str, str, Any]
 
-    from pip._internal.req.req_install import InstallRequirement
-
-    # Shorthands
-    PackageSet = Dict[str, 'PackageDetails']
-    Missing = Tuple[str, Any]
-    Conflicting = Tuple[str, str, Any]
-
-    MissingDict = Dict[str, List[Missing]]
-    ConflictingDict = Dict[str, List[Conflicting]]
-    CheckResult = Tuple[MissingDict, ConflictingDict]
-    ConflictDetails = Tuple[PackageSet, CheckResult]
+MissingDict = Dict[str, List[Missing]]
+ConflictingDict = Dict[str, List[Conflicting]]
+CheckResult = Tuple[MissingDict, ConflictingDict]
+ConflictDetails = Tuple[PackageSet, CheckResult]
 
 PackageDetails = namedtuple('PackageDetails', ['version', 'requires'])
 

src/pip/_internal/operations/freeze.py

@@ -1,10 +1,20 @@
 import collections
 import logging
 import os
-from typing import TYPE_CHECKING
+from typing import (
+    Container,
+    Dict,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Set,
+    Tuple,
+    Union,
+)
 
 from pip._vendor.packaging.utils import canonicalize_name
-from pip._vendor.pkg_resources import RequirementParseError
+from pip._vendor.pkg_resources import Distribution, Requirement, RequirementParseError
 
 from pip._internal.exceptions import BadCommand, InstallationError
 from pip._internal.req.constructors import (
@@ -18,26 +28,10 @@ from pip._internal.utils.direct_url_helpers import (
 )
 from pip._internal.utils.misc import dist_is_editable, get_installed_distributions
 
-if TYPE_CHECKING:
-    from typing import (
-        Container,
-        Dict,
-        Iterable,
-        Iterator,
-        List,
-        Optional,
-        Set,
-        Tuple,
-        Union,
-    )
-
-    from pip._vendor.pkg_resources import Distribution, Requirement
-
-    RequirementInfo = Tuple[Optional[Union[str, Requirement]], bool, List[str]]
-
-
 logger = logging.getLogger(__name__)
 
+RequirementInfo = Tuple[Optional[Union[str, Requirement]], bool, List[str]]
+
 
 def freeze(
     requirement=None,  # type: Optional[List[str]]

src/pip/_internal/operations/install/editable_legacy.py

@@ -1,18 +1,13 @@
 """Legacy editable installation process, i.e. `setup.py develop`.
 """
 import logging
-from typing import TYPE_CHECKING
+from typing import List, Optional, Sequence
 
+from pip._internal.build_env import BuildEnvironment
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.setuptools_build import make_setuptools_develop_args
 from pip._internal.utils.subprocess import call_subprocess
 
-if TYPE_CHECKING:
-    from typing import List, Optional, Sequence
-
-    from pip._internal.build_env import BuildEnvironment
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/operations/install/legacy.py

@@ -5,22 +5,17 @@ import logging
 import os
 import sys
 from distutils.util import change_root
-from typing import TYPE_CHECKING
+from typing import List, Optional, Sequence
 
+from pip._internal.build_env import BuildEnvironment
 from pip._internal.exceptions import InstallationError
+from pip._internal.models.scheme import Scheme
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.misc import ensure_dir
 from pip._internal.utils.setuptools_build import make_setuptools_install_args
 from pip._internal.utils.subprocess import runner_with_spinner_message
 from pip._internal.utils.temp_dir import TempDirectory
 
-if TYPE_CHECKING:
-    from typing import List, Optional, Sequence
-
-    from pip._internal.build_env import BuildEnvironment
-    from pip._internal.models.scheme import Scheme
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/operations/install/wheel.py

@@ -13,19 +13,38 @@ import shutil
 import sys
 import warnings
 from base64 import urlsafe_b64encode
+from email.message import Message
 from itertools import chain, filterfalse, starmap
-from typing import TYPE_CHECKING, cast
-from zipfile import ZipFile
+from typing import (
+    IO,
+    TYPE_CHECKING,
+    Any,
+    BinaryIO,
+    Callable,
+    Dict,
+    Iterable,
+    Iterator,
+    List,
+    NewType,
+    Optional,
+    Sequence,
+    Set,
+    Tuple,
+    Union,
+    cast,
+)
+from zipfile import ZipFile, ZipInfo
 
 from pip._vendor import pkg_resources
 from pip._vendor.distlib.scripts import ScriptMaker
 from pip._vendor.distlib.util import get_export_entry
+from pip._vendor.pkg_resources import Distribution
 from pip._vendor.six import ensure_str, ensure_text, reraise
 
 from pip._internal.exceptions import InstallationError
 from pip._internal.locations import get_major_minor_version
 from pip._internal.models.direct_url import DIRECT_URL_METADATA_NAME, DirectUrl
-from pip._internal.models.scheme import SCHEME_KEYS
+from pip._internal.models.scheme import SCHEME_KEYS, Scheme
 from pip._internal.utils.filesystem import adjacent_tmp_file, replace
 from pip._internal.utils.misc import captured_stdout, ensure_dir, hash_file, partition
 from pip._internal.utils.unpacking import (
@@ -37,32 +56,7 @@ from pip._internal.utils.unpacking import (
 from pip._internal.utils.wheel import parse_wheel, pkg_resources_distribution_for_wheel
 
 if TYPE_CHECKING:
-    from email.message import Message
-    from typing import (
-        IO,
-        Any,
-        BinaryIO,
-        Callable,
-        Dict,
-        Iterable,
-        Iterator,
-        List,
-        NewType,
-        Optional,
-        Protocol,
-        Sequence,
-        Set,
-        Tuple,
-        Union,
-    )
-    from zipfile import ZipInfo
-
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.models.scheme import Scheme
-
-    RecordPath = NewType('RecordPath', str)
-    InstalledCSVRow = Tuple[RecordPath, str, Union[int, str]]
+    from typing import Protocol
 
     class File(Protocol):
         src_record_path = None  # type: RecordPath
@@ -76,6 +70,9 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger(__name__)
 
+RecordPath = NewType('RecordPath', str)
+InstalledCSVRow = Tuple[RecordPath, str, Union[int, str]]
+
 
 def rehash(path, blocksize=1 << 20):
     # type: (str, int) -> Tuple[str, str]

src/pip/_internal/operations/prepare.py

@@ -8,9 +8,10 @@ import logging
 import mimetypes
 import os
 import shutil
-from typing import TYPE_CHECKING
+from typing import Dict, Iterable, List, Optional, Tuple
 
 from pip._vendor.packaging.utils import canonicalize_name
+from pip._vendor.pkg_resources import Distribution
 
 from pip._internal.distributions import make_distribution_for_install_requirement
 from pip._internal.distributions.installed import InstalledDistribution
@@ -23,33 +24,25 @@ from pip._internal.exceptions import (
     PreviousBuildDirError,
     VcsHashUnsupported,
 )
+from pip._internal.index.package_finder import PackageFinder
+from pip._internal.models.link import Link
 from pip._internal.models.wheel import Wheel
 from pip._internal.network.download import BatchDownloader, Downloader
 from pip._internal.network.lazy_wheel import (
     HTTPRangeRequestUnsupported,
     dist_from_wheel_url,
 )
+from pip._internal.network.session import PipSession
+from pip._internal.req.req_install import InstallRequirement
+from pip._internal.req.req_tracker import RequirementTracker
 from pip._internal.utils.filesystem import copy2_fixed
-from pip._internal.utils.hashes import MissingHashes
+from pip._internal.utils.hashes import Hashes, MissingHashes
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.misc import display_path, hide_url, path_to_display, rmtree
 from pip._internal.utils.temp_dir import TempDirectory
 from pip._internal.utils.unpacking import unpack_file
 from pip._internal.vcs import vcs
 
-if TYPE_CHECKING:
-    from typing import Dict, Iterable, List, Optional, Tuple
-
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.index.package_finder import PackageFinder
-    from pip._internal.models.link import Link
-    from pip._internal.network.session import PipSession
-    from pip._internal.req.req_install import InstallRequirement
-    from pip._internal.req.req_tracker import RequirementTracker
-    from pip._internal.utils.hashes import Hashes
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/pyproject.py

@@ -1,15 +1,12 @@
 import os
 from collections import namedtuple
-from typing import TYPE_CHECKING
+from typing import Any, List, Optional
 
 from pip._vendor import toml
 from pip._vendor.packaging.requirements import InvalidRequirement, Requirement
 
 from pip._internal.exceptions import InstallationError
 
-if TYPE_CHECKING:
-    from typing import Any, List, Optional
-
 
 def _is_list_of_str(obj):
     # type: (Any) -> bool

src/pip/_internal/req/__init__.py

@@ -1,6 +1,6 @@
 import collections
 import logging
-from typing import TYPE_CHECKING
+from typing import Iterator, List, Optional, Sequence, Tuple
 
 from pip._internal.utils.logging import indent_log
 
@@ -8,9 +8,6 @@ from .req_file import parse_requirements
 from .req_install import InstallRequirement
 from .req_set import RequirementSet
 
-if TYPE_CHECKING:
-    from typing import Iterator, List, Optional, Sequence, Tuple
-
 __all__ = [
     "RequirementSet", "InstallRequirement",
     "parse_requirements", "install_given_reqs",

src/pip/_internal/req/constructors.py

@@ -11,7 +11,7 @@ InstallRequirement.
 import logging
 import os
 import re
-from typing import TYPE_CHECKING
+from typing import Any, Dict, Optional, Set, Tuple, Union
 
 from pip._vendor.packaging.markers import Marker
 from pip._vendor.packaging.requirements import InvalidRequirement, Requirement
@@ -23,18 +23,13 @@ from pip._internal.models.index import PyPI, TestPyPI
 from pip._internal.models.link import Link
 from pip._internal.models.wheel import Wheel
 from pip._internal.pyproject import make_pyproject_path
+from pip._internal.req.req_file import ParsedRequirement
 from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.filetypes import is_archive_file
 from pip._internal.utils.misc import is_installable_dir
 from pip._internal.utils.urls import path_to_url
 from pip._internal.vcs import is_url, vcs
 
-if TYPE_CHECKING:
-    from typing import Any, Dict, Optional, Set, Tuple, Union
-
-    from pip._internal.req.req_file import ParsedRequirement
-
-
 __all__ = [
     "install_req_from_editable", "install_req_from_line",
     "parse_editable"

src/pip/_internal/req/req_file.py

@@ -7,39 +7,37 @@ import os
 import re
 import shlex
 import urllib.parse
-from typing import TYPE_CHECKING
+from optparse import Values
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Callable,
+    Dict,
+    Iterator,
+    List,
+    NoReturn,
+    Optional,
+    Text,
+    Tuple,
+)
 
 from pip._internal.cli import cmdoptions
 from pip._internal.exceptions import InstallationError, RequirementsFileParseError
 from pip._internal.models.search_scope import SearchScope
+from pip._internal.network.session import PipSession
 from pip._internal.network.utils import raise_for_status
 from pip._internal.utils.encoding import auto_decode
 from pip._internal.utils.urls import get_url_scheme, url_to_path
 
 if TYPE_CHECKING:
-    from optparse import Values
-    from typing import (
-        Any,
-        Callable,
-        Dict,
-        Iterator,
-        List,
-        NoReturn,
-        Optional,
-        Text,
-        Tuple,
-    )
-
     from pip._internal.index.package_finder import PackageFinder
-    from pip._internal.network.session import PipSession
-
-    ReqFileLines = Iterator[Tuple[int, Text]]
-
-    LineParser = Callable[[Text], Tuple[str, Values]]
-
 
 __all__ = ['parse_requirements']
 
+ReqFileLines = Iterator[Tuple[int, Text]]
+
+LineParser = Callable[[Text], Tuple[str, Values]]
+
 SCHEME_RE = re.compile(r'^(http|https|file):', re.I)
 COMMENT_RE = re.compile(r'(^|\s+)#.*$')
 

src/pip/_internal/req/req_install.py

@@ -7,16 +7,19 @@ import shutil
 import sys
 import uuid
 import zipfile
-from typing import TYPE_CHECKING
+from typing import Any, Dict, Iterable, List, Optional, Sequence, Union
 
 from pip._vendor import pkg_resources, six
+from pip._vendor.packaging.markers import Marker
 from pip._vendor.packaging.requirements import Requirement
+from pip._vendor.packaging.specifiers import SpecifierSet
 from pip._vendor.packaging.utils import canonicalize_name
 from pip._vendor.packaging.version import Version
 from pip._vendor.packaging.version import parse as parse_version
 from pip._vendor.pep517.wrappers import Pep517HookCaller
+from pip._vendor.pkg_resources import Distribution
 
-from pip._internal.build_env import NoOpBuildEnvironment
+from pip._internal.build_env import BuildEnvironment, NoOpBuildEnvironment
 from pip._internal.exceptions import InstallationError
 from pip._internal.locations import get_scheme
 from pip._internal.models.link import Link
@@ -51,16 +54,6 @@ from pip._internal.utils.temp_dir import TempDirectory, tempdir_kinds
 from pip._internal.utils.virtualenv import running_under_virtualenv
 from pip._internal.vcs import vcs
 
-if TYPE_CHECKING:
-    from typing import Any, Dict, Iterable, List, Optional, Sequence, Union
-
-    from pip._vendor.packaging.markers import Marker
-    from pip._vendor.packaging.specifiers import SpecifierSet
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.build_env import BuildEnvironment
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/req/req_set.py

@@ -1,19 +1,14 @@
 import logging
 from collections import OrderedDict
-from typing import TYPE_CHECKING
+from typing import Dict, Iterable, List, Optional, Tuple
 
 from pip._vendor.packaging.utils import canonicalize_name
 
 from pip._internal.exceptions import InstallationError
 from pip._internal.models.wheel import Wheel
+from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils import compatibility_tags
 
-if TYPE_CHECKING:
-    from typing import Dict, Iterable, List, Optional, Tuple
-
-    from pip._internal.req.req_install import InstallRequirement
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/req/req_tracker.py

@@ -2,17 +2,13 @@ import contextlib
 import hashlib
 import logging
 import os
-from typing import TYPE_CHECKING
+from types import TracebackType
+from typing import Dict, Iterator, Optional, Set, Type, Union
 
+from pip._internal.models.link import Link
+from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.temp_dir import TempDirectory
 
-if TYPE_CHECKING:
-    from types import TracebackType
-    from typing import Dict, Iterator, Optional, Set, Type, Union
-
-    from pip._internal.models.link import Link
-    from pip._internal.req.req_install import InstallRequirement
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/req/req_uninstall.py

@@ -5,9 +5,10 @@ import os
 import sys
 import sysconfig
 from importlib.util import cache_from_source
-from typing import TYPE_CHECKING
+from typing import Any, Callable, Dict, Iterable, Iterator, List, Optional, Set, Tuple
 
 from pip._vendor import pkg_resources
+from pip._vendor.pkg_resources import Distribution
 
 from pip._internal.exceptions import UninstallationError
 from pip._internal.locations import bin_py, bin_user
@@ -25,21 +26,6 @@ from pip._internal.utils.misc import (
 )
 from pip._internal.utils.temp_dir import AdjacentTempDirectory, TempDirectory
 
-if TYPE_CHECKING:
-    from typing import (
-        Any,
-        Callable,
-        Dict,
-        Iterable,
-        Iterator,
-        List,
-        Optional,
-        Set,
-        Tuple,
-    )
-
-    from pip._vendor.pkg_resources import Distribution
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/resolution/base.py

@@ -1,14 +1,11 @@
-from typing import TYPE_CHECKING
+from typing import Callable, List
 
-if TYPE_CHECKING:
-    from typing import Callable, List
+from pip._internal.req.req_install import InstallRequirement
+from pip._internal.req.req_set import RequirementSet
 
-    from pip._internal.req.req_install import InstallRequirement
-    from pip._internal.req.req_set import RequirementSet
-
-    InstallRequirementProvider = Callable[
-        [str, InstallRequirement], InstallRequirement
-    ]
+InstallRequirementProvider = Callable[
+    [str, InstallRequirement], InstallRequirement
+]
 
 
 class BaseResolver:

src/pip/_internal/resolution/legacy/resolver.py

@@ -18,10 +18,12 @@ import logging
 import sys
 from collections import defaultdict
 from itertools import chain
-from typing import TYPE_CHECKING
+from typing import DefaultDict, List, Optional, Set, Tuple
 
 from pip._vendor.packaging import specifiers
+from pip._vendor.pkg_resources import Distribution
 
+from pip._internal.cache import WheelCache
 from pip._internal.exceptions import (
     BestVersionAlreadyInstalled,
     DistributionNotFound,
@@ -29,30 +31,24 @@ from pip._internal.exceptions import (
     HashErrors,
     UnsupportedPythonVersion,
 )
-from pip._internal.req.req_install import check_invalid_constraint_type
+from pip._internal.index.package_finder import PackageFinder
+from pip._internal.models.link import Link
+from pip._internal.operations.prepare import RequirementPreparer
+from pip._internal.req.req_install import (
+    InstallRequirement,
+    check_invalid_constraint_type,
+)
 from pip._internal.req.req_set import RequirementSet
-from pip._internal.resolution.base import BaseResolver
+from pip._internal.resolution.base import BaseResolver, InstallRequirementProvider
 from pip._internal.utils.compatibility_tags import get_supported
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.misc import dist_in_usersite, normalize_version_info
 from pip._internal.utils.packaging import check_requires_python, get_requires_python
 
-if TYPE_CHECKING:
-    from typing import DefaultDict, List, Optional, Set, Tuple
-
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.cache import WheelCache
-    from pip._internal.index.package_finder import PackageFinder
-    from pip._internal.models.link import Link
-    from pip._internal.operations.prepare import RequirementPreparer
-    from pip._internal.req.req_install import InstallRequirement
-    from pip._internal.resolution.base import InstallRequirementProvider
-
-    DiscoveredDependencies = DefaultDict[str, List[InstallRequirement]]
-
 logger = logging.getLogger(__name__)
 
+DiscoveredDependencies = DefaultDict[str, List[InstallRequirement]]
+
 
 def _check_dist_requires_python(
     dist,  # type: Distribution

src/pip/_internal/resolution/resolvelib/base.py

@@ -1,22 +1,14 @@
-from typing import TYPE_CHECKING
+from typing import FrozenSet, Iterable, Optional, Tuple
 
 from pip._vendor.packaging.specifiers import SpecifierSet
 from pip._vendor.packaging.utils import canonicalize_name
+from pip._vendor.packaging.version import _BaseVersion
 
+from pip._internal.models.link import Link
 from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.hashes import Hashes
 
-if TYPE_CHECKING:
-    from typing import FrozenSet, Iterable, Optional, Tuple
-
-    from pip._vendor.packaging.version import _BaseVersion
-
-    from pip._internal.models.link import Link
-
-    CandidateLookup = Tuple[
-        Optional["Candidate"],
-        Optional[InstallRequirement],
-    ]
+CandidateLookup = Tuple[Optional["Candidate"], Optional[InstallRequirement]]
 
 
 def format_name(project, extras):

src/pip/_internal/resolution/resolvelib/candidates.py

@@ -1,12 +1,14 @@
 import logging
 import sys
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any, FrozenSet, Iterable, Optional, Tuple, Union
 
 from pip._vendor.packaging.specifiers import InvalidSpecifier, SpecifierSet
 from pip._vendor.packaging.utils import canonicalize_name
-from pip._vendor.packaging.version import Version
+from pip._vendor.packaging.version import Version, _BaseVersion
+from pip._vendor.pkg_resources import Distribution
 
 from pip._internal.exceptions import HashError, MetadataInconsistent
+from pip._internal.models.link import Link
 from pip._internal.models.wheel import Wheel
 from pip._internal.req.constructors import (
     install_req_from_editable,
@@ -16,28 +18,19 @@ from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.misc import dist_is_editable, normalize_version_info
 from pip._internal.utils.packaging import get_requires_python
 
-from .base import Candidate, format_name
+from .base import Candidate, Requirement, format_name
 
 if TYPE_CHECKING:
-    from typing import Any, FrozenSet, Iterable, Optional, Tuple, Union
-
-    from pip._vendor.packaging.version import _BaseVersion
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.models.link import Link
-
-    from .base import Requirement
     from .factory import Factory
 
-    BaseCandidate = Union[
-        "AlreadyInstalledCandidate",
-        "EditableCandidate",
-        "LinkCandidate",
-    ]
-
-
 logger = logging.getLogger(__name__)
 
+BaseCandidate = Union[
+    "AlreadyInstalledCandidate",
+    "EditableCandidate",
+    "LinkCandidate",
+]
+
 
 def make_install_req_from_link(link, template):
     # type: (Link, InstallRequirement) -> InstallRequirement

src/pip/_internal/resolution/resolvelib/factory.py

@@ -1,9 +1,25 @@
 import functools
 import logging
-from typing import TYPE_CHECKING
+from typing import (
+    Dict,
+    FrozenSet,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Sequence,
+    Set,
+    Tuple,
+    TypeVar,
+)
 
+from pip._vendor.packaging.specifiers import SpecifierSet
 from pip._vendor.packaging.utils import canonicalize_name
+from pip._vendor.packaging.version import _BaseVersion
+from pip._vendor.pkg_resources import Distribution
+from pip._vendor.resolvelib import ResolutionImpossible
 
+from pip._internal.cache import CacheEntry, WheelCache
 from pip._internal.exceptions import (
     DistributionNotFound,
     InstallationError,
@@ -12,8 +28,12 @@ from pip._internal.exceptions import (
     UnsupportedPythonVersion,
     UnsupportedWheel,
 )
+from pip._internal.index.package_finder import PackageFinder
+from pip._internal.models.link import Link
 from pip._internal.models.wheel import Wheel
+from pip._internal.operations.prepare import RequirementPreparer
 from pip._internal.req.req_install import InstallRequirement
+from pip._internal.resolution.base import InstallRequirementProvider
 from pip._internal.utils.compatibility_tags import get_supported
 from pip._internal.utils.hashes import Hashes
 from pip._internal.utils.misc import (
@@ -23,15 +43,16 @@ from pip._internal.utils.misc import (
 )
 from pip._internal.utils.virtualenv import running_under_virtualenv
 
-from .base import Constraint
+from .base import Candidate, Constraint, Requirement
 from .candidates import (
     AlreadyInstalledCandidate,
+    BaseCandidate,
     EditableCandidate,
     ExtrasCandidate,
     LinkCandidate,
     RequiresPythonCandidate,
 )
-from .found_candidates import FoundCandidates
+from .found_candidates import FoundCandidates, IndexCandidateInfo
 from .requirements import (
     ExplicitRequirement,
     RequiresPythonRequirement,
@@ -39,40 +60,11 @@ from .requirements import (
     UnsatisfiableRequirement,
 )
 
-if TYPE_CHECKING:
-    from typing import (
-        Dict,
-        FrozenSet,
-        Iterable,
-        Iterator,
-        List,
-        Optional,
-        Sequence,
-        Set,
-        Tuple,
-        TypeVar,
-    )
-
-    from pip._vendor.packaging.specifiers import SpecifierSet
-    from pip._vendor.packaging.version import _BaseVersion
-    from pip._vendor.pkg_resources import Distribution
-    from pip._vendor.resolvelib import ResolutionImpossible
-
-    from pip._internal.cache import CacheEntry, WheelCache
-    from pip._internal.index.package_finder import PackageFinder
-    from pip._internal.models.link import Link
-    from pip._internal.operations.prepare import RequirementPreparer
-    from pip._internal.resolution.base import InstallRequirementProvider
-
-    from .base import Candidate, Requirement
-    from .candidates import BaseCandidate
-    from .found_candidates import IndexCandidateInfo
-
-    C = TypeVar("C")
-    Cache = Dict[Link, C]
-
 logger = logging.getLogger(__name__)
 
+C = TypeVar("C")
+Cache = Dict[Link, C]
+
 
 class Factory:
     def __init__(

src/pip/_internal/resolution/resolvelib/found_candidates.py

@@ -9,18 +9,14 @@ something.
 """
 
 import functools
-from typing import TYPE_CHECKING
+from typing import Callable, Iterator, Optional, Set, Tuple
 
+from pip._vendor.packaging.version import _BaseVersion
 from pip._vendor.six.moves import collections_abc  # type: ignore
 
-if TYPE_CHECKING:
-    from typing import Callable, Iterator, Optional, Set, Tuple
+from .base import Candidate
 
-    from pip._vendor.packaging.version import _BaseVersion
-
-    from .base import Candidate
-
-    IndexCandidateInfo = Tuple[_BaseVersion, Callable[[], Optional[Candidate]]]
+IndexCandidateInfo = Tuple[_BaseVersion, Callable[[], Optional[Candidate]]]
 
 
 def _iter_built(infos):

src/pip/_internal/resolution/resolvelib/provider.py

@@ -1,14 +1,9 @@
-from typing import TYPE_CHECKING
+from typing import Any, Dict, Iterable, Optional, Sequence, Tuple, Union
 
 from pip._vendor.resolvelib.providers import AbstractProvider
 
-from .base import Constraint
-
-if TYPE_CHECKING:
-    from typing import Any, Dict, Iterable, Optional, Sequence, Tuple, Union
-
-    from .base import Candidate, Requirement
-    from .factory import Factory
+from .base import Candidate, Constraint, Requirement
+from .factory import Factory
 
 # Notes on the relationship between the provider, the factory, and the
 # candidate and requirement classes.

src/pip/_internal/resolution/resolvelib/reporter.py

@@ -1,14 +1,10 @@
 from collections import defaultdict
 from logging import getLogger
-from typing import TYPE_CHECKING
+from typing import Any, DefaultDict
 
 from pip._vendor.resolvelib.reporters import BaseReporter
 
-if TYPE_CHECKING:
-    from typing import Any, DefaultDict
-
-    from .base import Candidate, Requirement
-
+from .base import Candidate, Requirement
 
 logger = getLogger(__name__)
 

src/pip/_internal/resolution/resolvelib/requirements.py

@@ -1,15 +1,9 @@
-from typing import TYPE_CHECKING
-
+from pip._vendor.packaging.specifiers import SpecifierSet
 from pip._vendor.packaging.utils import canonicalize_name
 
-from .base import Requirement, format_name
+from pip._internal.req.req_install import InstallRequirement
 
-if TYPE_CHECKING:
-    from pip._vendor.packaging.specifiers import SpecifierSet
-
-    from pip._internal.req.req_install import InstallRequirement
-
-    from .base import Candidate, CandidateLookup
+from .base import Candidate, CandidateLookup, Requirement, format_name
 
 
 class ExplicitRequirement(Requirement):

src/pip/_internal/resolution/resolvelib/resolver.py

@@ -1,17 +1,24 @@
 import functools
 import logging
 import os
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Dict, List, Optional, Set, Tuple
 
 from pip._vendor import six
 from pip._vendor.packaging.utils import canonicalize_name
 from pip._vendor.resolvelib import ResolutionImpossible
 from pip._vendor.resolvelib import Resolver as RLResolver
+from pip._vendor.resolvelib.resolvers import Result
 
+from pip._internal.cache import WheelCache
 from pip._internal.exceptions import InstallationError
-from pip._internal.req.req_install import check_invalid_constraint_type
+from pip._internal.index.package_finder import PackageFinder
+from pip._internal.operations.prepare import RequirementPreparer
+from pip._internal.req.req_install import (
+    InstallRequirement,
+    check_invalid_constraint_type,
+)
 from pip._internal.req.req_set import RequirementSet
-from pip._internal.resolution.base import BaseResolver
+from pip._internal.resolution.base import BaseResolver, InstallRequirementProvider
 from pip._internal.resolution.resolvelib.provider import PipProvider
 from pip._internal.resolution.resolvelib.reporter import (
     PipDebuggingReporter,
@@ -25,18 +32,8 @@ from .base import Constraint
 from .factory import Factory
 
 if TYPE_CHECKING:
-    from typing import Dict, List, Optional, Set, Tuple
-
-    from pip._vendor.resolvelib.resolvers import Result
     from pip._vendor.resolvelib.structs import Graph
 
-    from pip._internal.cache import WheelCache
-    from pip._internal.index.package_finder import PackageFinder
-    from pip._internal.operations.prepare import RequirementPreparer
-    from pip._internal.req.req_install import InstallRequirement
-    from pip._internal.resolution.base import InstallRequirementProvider
-
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/self_outdated_check.py

@@ -2,9 +2,10 @@ import datetime
 import hashlib
 import json
 import logging
+import optparse
 import os.path
 import sys
-from typing import TYPE_CHECKING
+from typing import Any, Dict
 
 from pip._vendor.packaging.version import parse as parse_version
 
@@ -12,16 +13,10 @@ from pip._internal.index.collector import LinkCollector
 from pip._internal.index.package_finder import PackageFinder
 from pip._internal.metadata import get_default_environment
 from pip._internal.models.selection_prefs import SelectionPreferences
+from pip._internal.network.session import PipSession
 from pip._internal.utils.filesystem import adjacent_tmp_file, check_path_owner, replace
 from pip._internal.utils.misc import ensure_dir
 
-if TYPE_CHECKING:
-    import optparse
-    from typing import Any, Dict
-
-    from pip._internal.network.session import PipSession
-
-
 SELFCHECK_DATE_FMT = "%Y-%m-%dT%H:%M:%SZ"
 
 

src/pip/_internal/utils/appdirs.py

@@ -7,13 +7,10 @@ and eventually drop this after all usages are changed.
 """
 
 import os
-from typing import TYPE_CHECKING
+from typing import List
 
 from pip._vendor import appdirs as _appdirs
 
-if TYPE_CHECKING:
-    from typing import List
-
 
 def user_cache_dir(appname):
     # type: (str) -> str

src/pip/_internal/utils/compat.py

@@ -9,11 +9,7 @@ import locale
 import logging
 import os
 import sys
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from typing import Optional, Union
-
+from typing import Optional, Union
 
 __all__ = ["console_to_str", "get_path_uid", "stdlib_pkgs", "WINDOWS"]
 

src/pip/_internal/utils/compatibility_tags.py

@@ -2,7 +2,7 @@
 """
 
 import re
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, List, Optional, Tuple
 
 from pip._vendor.packaging.tags import (
     Tag,
@@ -15,10 +15,9 @@ from pip._vendor.packaging.tags import (
 )
 
 if TYPE_CHECKING:
-    from typing import List, Optional, Tuple
-
     from pip._vendor.packaging.tags import PythonVersion
 
+
 _osx_arch_pat = re.compile(r'(.+)_(\d+)_(\d+)_(.+)')
 
 

src/pip/_internal/utils/deprecation.py

@@ -7,16 +7,12 @@ A module that implements tooling to enable easy warnings about deprecations.
 
 import logging
 import warnings
-from typing import TYPE_CHECKING
+from typing import Any, Optional
 
 from pip._vendor.packaging.version import parse
 
 from pip import __version__ as current_version
 
-if TYPE_CHECKING:
-    from typing import Any, Optional
-
-
 DEPRECATION_MSG_PREFIX = "DEPRECATION: "
 
 

src/pip/_internal/utils/direct_url_helpers.py

@@ -1,6 +1,8 @@
 import json
 import logging
-from typing import TYPE_CHECKING
+from typing import Optional
+
+from pip._vendor.pkg_resources import Distribution
 
 from pip._internal.models.direct_url import (
     DIRECT_URL_METADATA_NAME,
@@ -10,15 +12,9 @@ from pip._internal.models.direct_url import (
     DirInfo,
     VcsInfo,
 )
+from pip._internal.models.link import Link
 from pip._internal.vcs import vcs
 
-if TYPE_CHECKING:
-    from typing import Optional
-
-    from pip._vendor.pkg_resources import Distribution
-
-    from pip._internal.models.link import Link
-
 logger = logging.getLogger(__name__)
 
 

src/pip/_internal/utils/distutils_args.py

@@ -1,10 +1,6 @@
 from distutils.errors import DistutilsArgError
 from distutils.fancy_getopt import FancyGetopt
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from typing import Dict, List
-
+from typing import Dict, List
 
 _options = [
     ("exec-prefix=", None, ""),

src/pip/_internal/utils/encoding.py

@@ -2,10 +2,7 @@ import codecs
 import locale
 import re
 import sys
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from typing import List, Tuple
+from typing import List, Tuple
 
 BOMS = [
     (codecs.BOM_UTF8, 'utf-8'),

src/pip/_internal/utils/entrypoints.py

@@ -1,11 +1,8 @@
 import sys
-from typing import TYPE_CHECKING
+from typing import List, Optional
 
 from pip._internal.cli.main import main
 
-if TYPE_CHECKING:
-    from typing import List, Optional
-
 
 def _wrapper(args=None):
     # type: (Optional[List[str]]) -> int

src/pip/_internal/utils/filesystem.py

@@ -7,7 +7,7 @@ import stat
 import sys
 from contextlib import contextmanager
 from tempfile import NamedTemporaryFile
-from typing import TYPE_CHECKING, cast
+from typing import Any, BinaryIO, Iterator, List, Union, cast
 
 # NOTE: retrying is not annotated in typeshed as on 2017-07-17, which is
 #       why we ignore the type on this import.
@@ -16,9 +16,6 @@ from pip._vendor.retrying import retry  # type: ignore
 from pip._internal.utils.compat import get_path_uid
 from pip._internal.utils.misc import format_size
 
-if TYPE_CHECKING:
-    from typing import Any, BinaryIO, Iterator, List, Union
-
 
 def check_path_owner(path):
     # type: (str) -> bool
@@ -96,7 +93,7 @@ def adjacent_tmp_file(path, **kwargs):
         suffix='.tmp',
         **kwargs
     ) as f:
-        result = cast('BinaryIO', f)
+        result = cast(BinaryIO, f)
         try:
             yield result
         finally:

src/pip/_internal/utils/filetypes.py

@@ -1,12 +1,10 @@
 """Filetype information.
 """
-from typing import TYPE_CHECKING
+
+from typing import Tuple
 
 from pip._internal.utils.misc import splitext
 
-if TYPE_CHECKING:
-    from typing import Tuple
-
 WHEEL_EXTENSION = '.whl'
 BZ2_EXTENSIONS = ('.tar.bz2', '.tbz')  # type: Tuple[str, ...]
 XZ_EXTENSIONS = ('.tar.xz', '.txz', '.tlz',