Adopt usedevelop=False for tests running in CI

.github/workflows/main.yml

@@ -22,6 +22,8 @@ jobs:
     runs-on: ${{ matrix.platform }}
     env:
       SETUPTOOLS_USE_DISTUTILS: ${{ matrix.distutils }}
+      PY_IGNORE_IMPORTMISMATCH: ${{ contains(matrix.python, 'pypy') && 1 }}
+      TOXENV: native
     steps:
       - uses: actions/checkout@v2
       - name: Setup Python
@@ -31,6 +33,14 @@ jobs:
       - name: Install tox
         run: |
           python -m pip install tox
+      - name: Skip some Pytest plugins on PyPy
+        if: contains(matrix.python, 'pypy') && matrix.distutils == 'local' && matrix.platform != 'windows-latest'
+        # PyPy 3.7 imports `distutils` in its `sysconfig`, which would trigger
+        # `_distutils_hack` and potentially mess imports for `pep517` (used by some plugins)
+        # https://foss.heptapod.net/pypy/pypy/-/blob/8301595a71447bbe58bb61c5ecd83d93cfda5eb0/lib-python/3/sysconfig.py#L461-473
+        # https://foss.heptapod.net/pypy/pypy/-/blob/8301595a71447bbe58bb61c5ecd83d93cfda5eb0/lib_pypy/_sysconfigdata.py#L5
+        # https://github.com/pypa/pep517/blob/a942316305395f8f757f210e2b16f738af73f8b8/pep517/in_process/_in_process.py#L76-L86
+        run: echo 'PYTEST_ADDOPTS=-p no:perf -p no:checkdocs' >> $GITHUB_ENV
       - name: Run tests
         run: tox -- --cov-report xml
       - name: Publish coverage
@@ -51,6 +61,7 @@ jobs:
     runs-on: windows-latest
     env:
       SETUPTOOLS_USE_DISTUTILS: ${{ matrix.distutils }}
+      TOXENV: native
     steps:
       - uses: actions/checkout@v2
       - name: Install Cygwin with Python and tox

conftest.py

@@ -1,9 +1,28 @@
+import os
 import sys
+from importlib.util import spec_from_file_location
 
 import pytest
 
 
-pytest_plugins = 'setuptools.tests.fixtures'
+class _ImportFinder:
+    """Allow in-tree pytest plugins when setuptools is installed from distribution"""
+
+    _root_dir = os.path.dirname(__file__)
+    _handled = ('setuptools.tests', 'pkg_resources.tests')
+
+    @classmethod
+    def find_spec(cls, fullname, _path, _target=None):
+        if all(not fullname.startswith(n) for n in cls._handled):
+            return None
+
+        loc = os.path.join(cls._root_dir, *fullname.split("."))
+        loc = os.path.join(loc, "__init__.py") if os.path.isdir(loc) else f"{loc}.py"
+        return spec_from_file_location(fullname, loc)
+
+
+sys.meta_path.append(_ImportFinder)
+pytest_plugins = ['setuptools.tests.fixtures']
 
 
 def pytest_addoption(parser):

pkg_resources/tests/test_pkg_resources.py

@@ -175,8 +175,10 @@ def test_setuptools_not_imported(self):
         that action doesn't cause setuptools to be imported.
         """
         lines = (
-            'import pkg_resources',
             'import sys',
+            'sys.modules.pop("setuptools", None)',
+            # ^-- make sure test does not fail if imported elsewhere
+            'import pkg_resources',
             (
                 'assert "setuptools" not in sys.modules, '
                 '"setuptools was imported"'

setuptools/tests/test_depends.py

@@ -2,15 +2,19 @@
 
 from setuptools import depends
 
+from . import __name__ as __pkg__
+
 
 class TestGetModuleConstant:
 
-    def test_basic(self):
+    def test_basic(self, monkeypatch):
         """
         Invoke get_module_constant on a module in
         the test package.
         """
-        mod_name = 'setuptools.tests.mod_with_constant'
+        mod_name = f'{__pkg__}.mod_with_constant'
+        monkeypatch.delitem(sys.modules, mod_name, None)
+        # ^-- make sure test does not fail if imported elsewhere
         val = depends.get_module_constant(mod_name, 'value')
         assert val == 'three, sir!'
-        assert 'setuptools.tests.mod_with_constant' not in sys.modules
+        assert mod_name not in sys.modules

setuptools/tests/test_easy_install.py

@@ -466,7 +466,7 @@ def test_setup_requires_honors_fetch_params(self, mock_index, monkeypatch):
                     with contexts.environment(PYTHONPATH=temp_install_dir):
                         cmd = [
                             sys.executable,
-                            '-m', 'setup',
+                            '-c', '__import__("setuptools").setup()',
                             'easy_install',
                             '--index-url', mock_index.url,
                             '--exclude-scripts',

setuptools/tests/test_namespaces.py

@@ -104,31 +104,18 @@ def test_namespace_package_installed_and_cwd(self, tmpdir):
         with test.test.paths_on_pythonpath([str(target)]):
             subprocess.check_call(pkg_resources_imp, cwd=str(pkg_A))
 
-    def test_packages_in_the_same_namespace_installed_and_cwd(self, tmpdir):
+    def test_packages_in_the_same_namespace_installed_and_cwd(self, tmpdir, venv):
         """
         Installing one namespace package and also have another in the same
         namespace in the current working directory, both of them must be
         importable.
         """
         pkg_A = namespaces.build_namespace_package(tmpdir, 'myns.pkgA')
         pkg_B = namespaces.build_namespace_package(tmpdir, 'myns.pkgB')
-        target = tmpdir / 'packages'
-        # use pip to install to the target directory
-        install_cmd = [
-            sys.executable,
-            '-m',
-            'pip.__main__',
-            'install',
-            str(pkg_A),
-            '-t', str(target),
-        ]
-        subprocess.check_call(install_cmd)
-        namespaces.make_site_dir(target)
 
-        # ensure that all packages import and pkg_resources imports
-        pkg_resources_imp = [
-            sys.executable,
-            '-c', 'import pkg_resources; import myns.pkgA; import myns.pkgB',
-        ]
-        with test.test.paths_on_pythonpath([str(target)]):
-            subprocess.check_call(pkg_resources_imp, cwd=str(pkg_B))
+        # Install pkgA regularly
+        venv.run(['python', '-m', 'pip', 'install', str(pkg_A)])
+
+        # ensure that all packages import when running from pkgB dir
+        cmd = ['python', '-c', 'import pkg_resources, myns.pkgA, myns.pkgB']
+        venv.run(cmd, cwd=str(pkg_B))

tox.ini

@@ -10,10 +10,14 @@ deps =
 	# Ideally all the dependencies should be set as "extras"
 commands =
 	pytest {posargs}
-usedevelop = True
+usedevelop =
+    native: False
+    !native: True
 extras = testing
 passenv =
 	SETUPTOOLS_USE_DISTUTILS
+	PY_IGNORE_IMPORTMISMATCH
+	PYTEST_ADDOPTS
 	windir  # required for test_pkg_resources
 	# honor git config in pytest-perf
 	HOME