feat: add async rest option in setup

gapic/templates/setup.py.j2

@@ -46,6 +46,12 @@ dependencies = [
     {% endif %}
     {% endfor %}
 ]
+extras = {
+    "async_rest": [
+        "google-api-core[grpc] >= 2.20.0, < 3.0.0dev",
+        "google-auth[aiohttp] >= 2.35.0, <3.0.0dev"
+    ],
+}
 url = "https://github.com/googleapis/google-cloud-python/tree/main/packages/{{ api.naming.warehouse_package_name }}"
 
 package_root = os.path.abspath(os.path.dirname(__file__))

gapic/templates/testing/_default_constraints.j2

@@ -1,7 +1,12 @@
+{# TODO(https://github.com/googleapis/gapic-generator-python/issues/2121): Remove the following variable (and the condition later in this file) for async rest transport once support for it is GA. #}
+{% set rest_async_io_enabled = api.all_library_settings[api.naming.proto_package].python_settings.experimental_features.rest_async_io_enabled %}
 {% from '_pypi_packages.j2' import pypi_packages %}
 # This constraints file is required for unit tests.
 # List all library dependencies and extras in this file.
 google-api-core
+{% if rest_async_io_enabled %}
+google-auth[aiohttp]==2.35.0
+{% endif %}
 proto-plus
 protobuf
 {% for package_tuple, package_info in pypi_packages.items() %}

gapic/templates/testing/constraints-3.7.txt.j2

@@ -1,12 +1,19 @@
+{# TODO(https://github.com/googleapis/gapic-generator-python/issues/2121): Remove the following variable (and the condition later in this file) for async rest transport once support for it is GA. #}
+{% set rest_async_io_enabled = api.all_library_settings[api.naming.proto_package].python_settings.experimental_features.rest_async_io_enabled %}
 {% from '_pypi_packages.j2' import pypi_packages %}
 # This constraints file is used to check that lower bounds
 # are correct in setup.py
 # List all library dependencies and extras in this file.
 # Pin the version to the lower bound.
 # e.g., if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have google-cloud-foo==1.14.0
+{% if rest_async_io_enabled %}
+google-api-core==2.20.0
+google-auth[aiohttp]==2.35.0
+{% else %}
 google-api-core==1.34.1
 google-auth==2.14.1
+{% endif %}
 proto-plus==1.22.3
 protobuf==3.20.2
 {% for package_tuple, package_info in pypi_packages.items() %}

noxfile.py

@@ -363,8 +363,6 @@ def showcase_w_rest_async(
             ignore_path = test_directory / ignore_file
             pytest_command.extend(["--ignore", str(ignore_path)])
 
-        # Note: google-auth is re-installed here with aiohttp option to override the version installed in constraints.
-        session.install('--no-cache-dir', '--force-reinstall', "google-auth[aiohttp]")
         session.run(
             *pytest_command,
             env=env,
@@ -485,8 +483,6 @@ def showcase_unit_w_rest_async(
     """Run the generated unit tests with async rest transport against the Showcase library."""
     with showcase_library(session, templates=templates, other_opts=other_opts, rest_async_io_enabled=True) as lib:
         session.chdir(lib)
-        # Note: google-auth is re-installed here with aiohttp option to override the version installed in constraints.
-        session.install('--no-cache-dir', '--force-reinstall', "google-auth[aiohttp]")
         run_showcase_unit_tests(session, rest_async_io_enabled=True)