Plumb through venv build isolation

src/pip/_internal/build_env/__init__.py

@@ -6,5 +6,6 @@
 from pip._internal.build_env._base import BuildEnvironment, get_runnable_pip
 from pip._internal.build_env._custom import CustomBuildEnvironment
 from pip._internal.build_env._noop import NoOpBuildEnvironment
+from pip._internal.build_env._venv import VenvBuildEnvironment
 
 BuildIsolationMode = Literal["noop", "custom", "venv"]

src/pip/_internal/build_env/_noop.py

@@ -1,8 +1,10 @@
 from types import TracebackType
-from typing import List, Optional, Type, Iterable
+from typing import TYPE_CHECKING, Iterable, List, Optional, Type
 
 from pip._internal.build_env import BuildEnvironment
-from pip._internal.index.package_finder import PackageFinder
+
+if TYPE_CHECKING:
+    from pip._internal.index.package_finder import PackageFinder
 
 
 class NoOpBuildEnvironment(BuildEnvironment):

src/pip/_internal/cli/cmdoptions.py

@@ -984,6 +984,7 @@ def check_list_path_option(options: Values) -> None:
         "fast-deps",
         "truststore",
         "no-binary-enable-wheel-cache",
+        "venv-isolation",
     ],
     help="Enable new functionality, that may be backward incompatible.",
 )

src/pip/_internal/cli/req_command.py

@@ -308,6 +308,8 @@ def make_requirement_preparer(
 
         if not options.build_isolation:
             build_isolation: BuildIsolationMode = "noop"
+        elif "venv-isolation" in options.features_enabled:
+            build_isolation = "venv"
         else:
             build_isolation = "custom"
 

src/pip/_internal/distributions/sdist.py

@@ -1,7 +1,11 @@
 import logging
 from typing import Iterable, Set, Tuple
 
-from pip._internal.build_env import BuildIsolationMode, CustomBuildEnvironment
+from pip._internal.build_env import (
+    BuildIsolationMode,
+    CustomBuildEnvironment,
+    VenvBuildEnvironment,
+)
 from pip._internal.distributions.base import AbstractDistribution
 from pip._internal.exceptions import InstallationError
 from pip._internal.index.package_finder import PackageFinder
@@ -35,7 +39,7 @@ def prepare_distribution_metadata(
         if should_isolate:
             # Setup an isolated environment and install the build backend static
             # requirements in it.
-            self._prepare_build_backend(finder)
+            self._prepare_build_backend(finder, build_isolation)
             # Check that if the requirement is editable, it either supports PEP 660 or
             # has a setup.py or a setup.cfg. This cannot be done earlier because we need
             # to setup the build backend to verify it supports build_editable, nor can
@@ -60,13 +64,18 @@ def prepare_distribution_metadata(
                 self._raise_missing_reqs(missing)
         self.req.prepare_metadata()
 
-    def _prepare_build_backend(self, finder: PackageFinder) -> None:
+    def _prepare_build_backend(
+        self, finder: PackageFinder, build_isolation: BuildIsolationMode
+    ) -> None:
         # Isolate in a BuildEnvironment and install the build-time
         # requirements.
         pyproject_requires = self.req.pyproject_requires
         assert pyproject_requires is not None
 
-        self.req.build_env = CustomBuildEnvironment()
+        if build_isolation == "custom":
+            self.req.build_env = CustomBuildEnvironment()
+        else:
+            self.req.build_env = VenvBuildEnvironment()
         self.req.build_env.install_requirements(
             finder, pyproject_requires, "overlay", kind="build dependencies"
         )