1 files changed, 76 insertions, 0 deletions
diff --git a/setuptools/tests/test_distutils_adoption.py b/setuptools/tests/test_distutils_adoption.py
new file mode 100644
index 00000000..b6b9c00e
--- /dev/null
+++ b/setuptools/tests/test_distutils_adoption.py
@@ -0,0 +1,76 @@
+import os
+import sys
+import functools
+import subprocess
+import platform
+
+import pytest
+import jaraco.envs
+import path
+
+
+IS_PYPY = '__pypy__' in sys.builtin_module_names
+
+
+class VirtualEnv(jaraco.envs.VirtualEnv):
+    name = '.env'
+    # Some version of PyPy will import distutils on startup, implicitly
+    # importing setuptools, and thus leading to BackendInvalid errors
+    # when upgrading Setuptools. Bypass this behavior by avoiding the
+    # early availability and need to upgrade.
+    create_opts = ['--no-setuptools']
+
+    def run(self, cmd, *args, **kwargs):
+        cmd = [self.exe(cmd[0])] + cmd[1:]
+        return subprocess.check_output(cmd, *args, cwd=self.root, **kwargs)
+
+
+@pytest.fixture
+def venv(tmp_path, tmp_src):
+    env = VirtualEnv()
+    env.root = path.Path(tmp_path / 'venv')
+    env.req = str(tmp_src)
+    return env.create()
+
+
+def popen_text(call):
+    """
+    Augment the Popen call with the parameters to ensure unicode text.
+    """
+    return functools.partial(call, universal_newlines=True) \
+        if sys.version_info < (3, 7) else functools.partial(call, text=True)
+
+
+def find_distutils(venv, imports='distutils', env=None, **kwargs):
+    py_cmd = 'import {imports}; print(distutils.__file__)'.format(**locals())
+    cmd = ['python', '-c', py_cmd]
+    if platform.system() == 'Windows':
+        env['SYSTEMROOT'] = os.environ['SYSTEMROOT']
+    return popen_text(venv.run)(cmd, env=env, **kwargs)
+
+
+def test_distutils_stdlib(venv):
+    """
+    Ensure stdlib distutils is used when appropriate.
+    """
+    env = dict(SETUPTOOLS_USE_DISTUTILS='stdlib')
+    assert venv.name not in find_distutils(venv, env=env).split(os.sep)
+
+
+def test_distutils_local_with_setuptools(venv):
+    """
+    Ensure local distutils is used when appropriate.
+    """
+    env = dict(SETUPTOOLS_USE_DISTUTILS='local')
+    loc = find_distutils(venv, imports='setuptools, distutils', env=env)
+    assert venv.name in loc.split(os.sep)
+
+
+@pytest.mark.xfail('IS_PYPY', reason='pypy imports distutils on startup')
+def test_distutils_local(venv):
+    """
+    Even without importing, the setuptools-local copy of distutils is
+    preferred.
+    """
+    env = dict(SETUPTOOLS_USE_DISTUTILS='local')
+    assert venv.name in find_distutils(venv, env=env).split(os.sep)