Remove pkg_resources usages from req_install

src/pip/_internal/req/req_install.py

@@ -10,7 +10,6 @@ import uuid
 import zipfile
 from typing import Any, Collection, Dict, Iterable, List, Optional, Sequence, Union
 
-from pip._vendor import pkg_resources
 from pip._vendor.packaging.markers import Marker
 from pip._vendor.packaging.requirements import Requirement
 from pip._vendor.packaging.specifiers import SpecifierSet
@@ -54,6 +53,7 @@ from pip._internal.utils.misc import (
     hide_url,
     redact_auth_from_url,
 )
+from pip._internal.utils.packaging import safe_extra
 from pip._internal.utils.subprocess import runner_with_spinner_message
 from pip._internal.utils.temp_dir import TempDirectory, tempdir_kinds
 from pip._internal.utils.virtualenv import running_under_virtualenv
@@ -119,15 +119,14 @@ class InstallRequirement:
         if extras:
             self.extras = extras
         elif req:
-            self.extras = {pkg_resources.safe_extra(extra) for extra in req.extras}
+            self.extras = {safe_extra(extra) for extra in req.extras}
         else:
             self.extras = set()
         if markers is None and req:
             markers = req.marker
         self.markers = markers
 
-        # This holds the pkg_resources.Distribution object if this requirement
-        # is already available:
+        # This holds the Distribution object if this requirement is already installed.
         self.satisfied_by: Optional[BaseDistribution] = None
         # Whether the installation process should try to uninstall an existing
         # distribution before installing this requirement.
@@ -216,7 +215,7 @@ class InstallRequirement:
     def name(self) -> Optional[str]:
         if self.req is None:
             return None
-        return pkg_resources.safe_name(self.req.name)
+        return self.req.name
 
     @functools.lru_cache()  # use cached_property in python 3.8+
     def supports_pyproject_editable(self) -> bool:

src/pip/_internal/utils/packaging.py

@@ -1,10 +1,13 @@
 import functools
 import logging
-from typing import Optional, Tuple
+import re
+from typing import NewType, Optional, Tuple, cast
 
 from pip._vendor.packaging import specifiers, version
 from pip._vendor.packaging.requirements import Requirement
 
+NormalizedExtra = NewType("NormalizedExtra", str)
+
 logger = logging.getLogger(__name__)
 
 
@@ -40,3 +43,15 @@ def get_requirement(req_string: str) -> Requirement:
     # minimize repeated parsing of the same string to construct equivalent
     # Requirement objects.
     return Requirement(req_string)
+
+
+def safe_extra(extra: str) -> NormalizedExtra:
+    """Convert an arbitrary string to a standard 'extra' name
+
+    Any runs of non-alphanumeric characters are replaced with a single '_',
+    and the result is always lowercased.
+
+    This function is duplicated from ``pkg_resources``. Note that this is not
+    the same to either ``canonicalize_name`` or ``_egg_link_name``.
+    """
+    return cast(NormalizedExtra, re.sub("[^A-Za-z0-9.-]+", "_", extra).lower())