Split _setup_isolation for readability

src/pip/_internal/distributions/sdist.py

@@ -32,33 +32,22 @@ def prepare_distribution_metadata(
  # Set up the build isolation, if this requirement should be isolated
  should_isolate = self.req.use_pep517 and build_isolation
  if should_isolate:
- self._setup_isolation(finder)
+ # Setup an isolated environment and install the build backend static
+ # requirements in it.
+ self._prepare_build_backend(finder)
+ # 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
+ # it be done later, because we want to avoid installing build requirements
+ # needlessly. Doing it here also works around setuptools generating
+ # UNKNOWN.egg-info when running get_requires_for_build_wheel on a directory
+ # without setup.py nor setup.cfg.
+ self.req.isolated_editable_sanity_check()
+ # Install the dynamic build requirements.
+ self._install_build_reqs(finder)
 
  self.req.prepare_metadata()
 
- def _setup_isolation(self, finder: PackageFinder) -> None:
- self._prepare_build_backend(finder)
- # 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 it be done
- # later, because we want to avoid installing build requirements needlessly.
- # Doing it here also works around setuptools generating UNKNOWN.egg-info when
- # running get_requires_for_build_wheel on a directory without setup.py nor
- # setup.cfg.
- self.req.isolated_editable_sanity_check()
- # Install any extra build dependencies that the backend requests.
- # This must be done in a second pass, as the pyproject.toml
- # dependencies must be installed before we can call the backend.
- if (
- self.req.editable
- and self.req.permit_editable_wheels
- and self.req.supports_pyproject_editable()
- ):
- build_reqs = self._get_build_requires_editable()
- else:
- build_reqs = self._get_build_requires_wheel()
- self._install_build_reqs(finder, build_reqs)
-
  def _prepare_build_backend(self, finder: PackageFinder) -> None:
  # Isolate in a BuildEnvironment and install the build-time
  # requirements.
@@ -103,8 +92,19 @@ def _get_build_requires_editable(self) -> Iterable[str]:
  with backend.subprocess_runner(runner):
  return backend.get_requires_for_build_editable()
 
- def _install_build_reqs(self, finder: PackageFinder, reqs: Iterable[str]) -> None:
- conflicting, missing = self.req.build_env.check_requirements(reqs)
+ def _install_build_reqs(self, finder: PackageFinder) -> None:
+ # Install any extra build dependencies that the backend requests.
+ # This must be done in a second pass, as the pyproject.toml
+ # dependencies must be installed before we can call the backend.
+ if (
+ self.req.editable
+ and self.req.permit_editable_wheels
+ and self.req.supports_pyproject_editable()
+ ):
+ build_reqs = self._get_build_requires_editable()
+ else:
+ build_reqs = self._get_build_requires_wheel()
+ conflicting, missing = self.req.build_env.check_requirements(build_reqs)
  if conflicting:
  self._raise_conflicts("the backend dependencies", conflicting)
  self.req.build_env.install_requirements(