feat: Introduce compatibility with native namespace packages (#561)

* feat: Introduce compatibility with native namespace packages

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: parthea

google/__init__.py

@@ -63,15 +63,11 @@
 # Only include packages under the 'google' namespace. Do not include tests,
 # benchmarks, etc.
 packages = [
-    package for package in setuptools.find_packages() if package.startswith("google")
+    package
+    for package in setuptools.find_namespace_packages()
+    if package.startswith("google")
 ]
 
-# Determine which namespaces are needed.
-namespaces = ["google"]
-if "google.cloud" in packages:
-    namespaces.append("google.cloud")
-
-
 setuptools.setup(
     name=name,
     version=version,
@@ -97,7 +93,6 @@
     ],
     platforms="Posix; MacOS X; Windows",
     packages=packages,
-    namespace_packages=namespaces,
     install_requires=dependencies,
     extras_require=extras,
     python_requires=">=3.7",

setup.py

@@ -0,0 +1,28 @@
+# Copyright 2023 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-api-core``.
+    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)