Split _setup_isolation for readability

src/pip/_internal/distributions/sdist.py

@@ -32,32 +32,24 @@ 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. For regular requirements such a sanity
+ # check is done in load_pyproject_toml. For editables this cannot be done
+ # earlier because we support editable installation of projects with
+ # pyproject.toml with setup.cfg and no setup.py (sigh). And we need to setup
+ # the build backend to verify it supports build_editable. It also can not be
+ # done later, because merely calling get_requires_for_build_wheel() for the
+ # setuptools __legacy__ backend creates the egg-info directory, including
+ # UNKNOWN.egg-info if it is misconfigured, and we don't want that.
+ 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 merely calling _get_build_requires_wheel()
- # for the setuptools __legacy__ backend creates the egg-info directory,
- # including UNKNOWN.egg-info if it is misconfigured, and we don't want that.
- 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.
@@ -102,8 +94,19 @@ 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(