utils/env: use isolated build for build.py envs

src/poetry/utils/env/__init__.py

@@ -35,7 +35,8 @@
     from collections.abc import Iterator
 
     from cleo.io.io import IO
-    from poetry.core.poetry import Poetry as CorePoetry
+
+    from poetry.poetry import Poetry
 
 
 @contextmanager
@@ -56,7 +57,7 @@ def ephemeral_environment(
 
 @contextmanager
 def build_environment(
-    poetry: CorePoetry, env: Env | None = None, io: IO | None = None
+    poetry: Poetry, env: Env | None = None, io: IO | None = None
 ) -> Iterator[Env]:
     """
     If a build script is specified for the project, there could be additional build
@@ -66,7 +67,10 @@ def build_environment(
     environment is returned.
     """
     if not env or poetry.package.build_script:
-        with ephemeral_environment(executable=env.python if env else None) as venv:
+        with ephemeral_environment(
+            executable=env.python if env else None,
+            flags={"no-pip": True, "no-setuptools": True, "no-wheel": True},
+        ) as venv:
             if io:
                 requires = [
                     f"<c1>{requirement}</c1>"
@@ -78,16 +82,10 @@ def build_environment(
                     f" {', '.join(requires)}"
                 )
 
-            output = venv.run_pip(
-                "install",
-                "--disable-pip-version-check",
-                "--ignore-installed",
-                "--no-input",
-                *poetry.pyproject.build_system.requires,
-            )
+            from poetry.utils.isolated_build import IsolatedEnv
 
-            if io and io.is_debug() and output:
-                io.write_error(output)
+            isolated_env = IsolatedEnv(venv, poetry.pool)
+            isolated_env.install(poetry.pyproject.build_system.requires)
 
             yield venv
     else:

tests/utils/env/test_env.py

@@ -24,13 +24,17 @@
 from poetry.utils.env import SystemEnv
 from poetry.utils.env import VirtualEnv
 from poetry.utils.env import build_environment
+from poetry.utils.env import ephemeral_environment
 
 
 if TYPE_CHECKING:
+    from typing import Iterator
+
     from pytest_mock import MockerFixture
 
     from poetry.poetry import Poetry
     from tests.types import FixtureDirGetter
+    from tests.types import SetProjectContext
 
 MINIMAL_SCRIPT = """\
 
@@ -463,35 +467,29 @@ def test_env_finds_fallback_executables_for_generic_env(
 
 
 @pytest.fixture
-def extended_without_setup_poetry(fixture_dir: FixtureDirGetter) -> Poetry:
-    poetry = Factory().create_poetry(fixture_dir("extended_project_without_setup"))
-
-    return poetry
+def extended_without_setup_poetry(
+    fixture_dir: FixtureDirGetter, set_project_context: SetProjectContext
+) -> Iterator[Poetry]:
+    with set_project_context("extended_project_without_setup") as cwd:
+        yield Factory().create_poetry(cwd)
 
 
 def test_build_environment_called_build_script_specified(
-    mocker: MockerFixture, extended_without_setup_poetry: Poetry, tmp_path: Path
+    mocker: MockerFixture,
+    extended_without_setup_poetry: Poetry,
 ) -> None:
-    project_env = MockEnv(path=tmp_path / "project")
-    ephemeral_env = MockEnv(path=tmp_path / "ephemeral")
+    patched_install = mocker.patch("poetry.utils.isolated_build.IsolatedEnv.install")
 
-    mocker.patch(
-        "poetry.utils.env.ephemeral_environment"
-    ).return_value.__enter__.return_value = ephemeral_env
+    with ephemeral_environment() as project_env:
+        import poetry.utils.env
+
+        spy = mocker.spy(poetry.utils.env, "ephemeral_environment")
+
+        with build_environment(extended_without_setup_poetry, project_env):
+            assert patched_install.call_count == 1
+            assert patched_install.call_args == mocker.call(["poetry-core", "cython"])
 
-    with build_environment(extended_without_setup_poetry, project_env) as env:
-        assert env == ephemeral_env
-        assert env.executed == [  # type: ignore[attr-defined]
-            [
-                str(sys.executable),
-                str(env.pip_embedded),
-                "install",
-                "--disable-pip-version-check",
-                "--ignore-installed",
-                "--no-input",
-                *extended_without_setup_poetry.pyproject.build_system.requires,
-            ]
-        ]
+        assert spy.call_count == 1
 
 
 def test_build_environment_not_called_without_build_script_specified(