TST: apply environment variable cleanup to all tests

This has no adverse consequence and makes it impossible to forget to
add it to relevant tests, which is important because the tests are not
commonly run with the environment variables set, making the failure
hard to discover.

Author: dnicolodi

tests/conftest.py

@@ -183,3 +183,12 @@ def disable_pip_version_check():
     mpatch = pytest.MonkeyPatch()
     yield mpatch.setenv('PIP_DISABLE_PIP_VERSION_CHECK', '1')
     mpatch.undo()
+
+
+@pytest.fixture(autouse=True, scope='session')
+def cleanenv():
+    # Cannot use the 'monkeypatch' fixture because of scope mismatch.
+    mpatch = pytest.MonkeyPatch()
+    # $MACOSX_DEPLOYMENT_TARGET affects the computation of the platform tag on macOS.
+    yield mpatch.delenv('MACOSX_DEPLOYMENT_TARGET', raising=False)
+    mpatch.undo()

tests/test_tags.py

@@ -40,13 +40,7 @@ def get_abi3_suffix():
 ABI3SUFFIX = get_abi3_suffix()
 
 
-@pytest.fixture()
-def cleanenv(monkeypatch):
-    # $MACOSX_DEPLOYMENT_TARGET affects the computation of the platform tag on macOS.
-    monkeypatch.delenv('MACOSX_DEPLOYMENT_TARGET', raising=False)
-
-
-def test_wheel_tag(cleanenv):
+def test_wheel_tag():
     assert str(mesonpy._tags.Tag()) == f'{INTERPRETER}-{ABI}-{PLATFORM}'
     assert str(mesonpy._tags.Tag(abi='abi3')) == f'{INTERPRETER}-abi3-{PLATFORM}'
 
@@ -118,14 +112,14 @@ def test_tag_purelib_wheel():
     assert str(builder.tag) == 'py3-none-any'
 
 
-def test_tag_platlib_wheel(cleanenv):
+def test_tag_platlib_wheel():
     builder = wheel_builder_test_factory({
         'platlib': [f'extension{SUFFIX}'],
     })
     assert str(builder.tag) == f'{INTERPRETER}-{ABI}-{PLATFORM}'
 
 
-def test_tag_stable_abi(cleanenv):
+def test_tag_stable_abi():
     builder = wheel_builder_test_factory({
         'platlib': [f'extension{ABI3SUFFIX}'],
     }, limited_api=True)
@@ -136,7 +130,7 @@ def test_tag_stable_abi(cleanenv):
 
 @pytest.mark.xfail(sys.version_info < (3, 8) and sys.platform == 'win32', reason='Extension modules suffix without ABI tags')
 @pytest.mark.xfail('__pypy__' in sys.builtin_module_names, reason='PyPy does not support the stable ABI')
-def test_tag_mixed_abi(cleanenv):
+def test_tag_mixed_abi():
     builder = wheel_builder_test_factory({
         'platlib': [f'extension{ABI3SUFFIX}', f'another{SUFFIX}'],
     }, pure=False, limited_api=True)