feat: Introduce compatibility with native namespace packages

noxfile.py

@@ -82,7 +82,7 @@ def mypy(session):
         "types-six",
         "types-mock",
     )
-    session.run("mypy", "google/", "tests/", "tests_async/")
+    session.run("mypy", "-p", "google", "-p", "tests", "-p", "tests_async")
 
 
 @nox.session(python=["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"])

setup.py

@@ -15,7 +15,7 @@
 import io
 import os
 
-from setuptools import find_packages
+from setuptools import find_namespace_packages
 from setuptools import setup
 
 
@@ -58,8 +58,9 @@
     description="Google Authentication Library",
     long_description=long_description,
     url="https://github.com/googleapis/google-auth-library-python",
-    packages=find_packages(exclude=("tests*", "system_tests*")),
-    namespace_packages=("google",),
+    packages=find_namespace_packages(
+        exclude=("tests*", "system_tests*", "docs*", "samples*")
+    ),
     install_requires=DEPENDENCIES,
     extras_require=extras,
     python_requires=">=3.6",

tests/test_packaging.py

@@ -0,0 +1,30 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+import subprocess
+import sys
+
+
+def test_namespace_package_compat(tmp_path):
+    """
+    The ``google`` namespace package should not be masked
+    by the presence of ``google-auth``.
+    """
+    google = tmp_path / "google"
+    google.mkdir()
+    google.joinpath("othermod.py").write_text("")
+    env = dict(os.environ, PYTHONPATH=str(tmp_path))
+    cmd = [sys.executable, "-m", "google.othermod"]
+    subprocess.check_call(cmd, env=env)