feat: implement async rest transport constructor

.github/workflows/tests.yaml

@@ -140,7 +140,8 @@ jobs:
     strategy:
       matrix:
         python: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
-        variant: ['', _alternative_templates, _mixins, _alternative_templates_mixins]
+        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2121) Remove `_w_rest_async` variant when async rest is GA.
+        variant: ['', _alternative_templates, _mixins, _alternative_templates_mixins, _w_rest_async]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4

gapic/generator/generator.py

@@ -294,9 +294,12 @@ def _render_template(
                         ('transport' in template_name
                          and not self._is_desired_transport(template_name, opts))
                         or
-                        # TODO(yon-mg) - remove when rest async implementation resolved
-                        # temporarily stop async client gen while rest async is unkown
-                        ('async' in template_name and 'grpc' not in opts.transport)
+                        # TODO(https://github.com/googleapis/gapic-generator-python/issues/2121): Remove this condition when async rest is GA.
+                        ('async_client' in template_name and 'grpc' not in opts.transport and
+                         not api_schema.all_library_settings[api_schema.naming.proto_package].python_settings.experimental_features.rest_async_io_enabled)
+                        or
+                        ('rest_asyncio' in template_name and
+                         not api_schema.all_library_settings[api_schema.naming.proto_package].python_settings.experimental_features.rest_async_io_enabled)
                         or
                         ('rest_base' in template_name and 'rest' not in opts.transport)
                 ):

gapic/templates/%namespace/%name_%version/%sub/services/%service/client.py.j2

@@ -1,3 +1,5 @@
+{# 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 %}
 {% extends '_base.py.j2' %}
 
 {% block content %}
@@ -62,6 +64,10 @@ from .transports.grpc_asyncio import {{ service.grpc_asyncio_transport_name }}
 {% endif %}
 {% if 'rest' in opts.transport %}
 from .transports.rest import {{ service.name }}RestTransport
+{# TODO(#2121): Remove this condition when async rest is GA. #}
+{% if rest_async_io_enabled %}
+from .transports.rest_asyncio import Async{{ service.name }}RestTransport
+{% endif %}{# if rest_async_io_enabled #}
 {% endif %}
 
 
@@ -79,6 +85,10 @@ class {{ service.client_name }}Meta(type):
     {% endif %}
     {% if "rest" in opts.transport %}
     _transport_registry["rest"] = {{ service.name }}RestTransport
+    {# TODO(#2121): Remove this condition when async rest is GA. #}
+    {% if rest_async_io_enabled %}
+    _transport_registry["rest_asyncio"] = Async{{ service.name }}RestTransport
+    {% endif %}{# if rest_async_io_enabled #}
     {% endif %}
 
     def get_transport_class(cls,

gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/rest_asyncio.py.j2

@@ -0,0 +1,80 @@
+{# 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 %}
+{% extends '_base.py.j2' %}
+
+{% block content %}
+
+from google.api_core import gapic_v1
+
+from typing import Any, Optional
+
+from .rest_base import _Base{{ service.name }}RestTransport
+
+from .base import DEFAULT_CLIENT_INFO as BASE_DEFAULT_CLIENT_INFO
+
+{# TODO (https://github.com/googleapis/gapic-generator-python/issues/2128): Update `rest_version` to include the transport dependency version. #}
+DEFAULT_CLIENT_INFO = gapic_v1.client_info.ClientInfo(
+    gapic_version=BASE_DEFAULT_CLIENT_INFO.gapic_version,
+    grpc_version=None,
+    rest_version=None,
+)
+
+class Async{{service.name}}RestTransport(_Base{{ service.name }}RestTransport):
+    """Asynchronous REST backend transport for {{ service.name }}.
+
+    {{ service.meta.doc|rst(width=72, indent=4) }}
+
+    This class defines the same methods as the primary client, so the
+    primary client can load the underlying transport implementation
+    and call it.
+
+    It sends JSON representations of protocol buffers over HTTP/1.1
+    """
+    def __init__(self, *,
+            host: str{% if service.host %} = '{{ service.host }}'{% endif %},
+            {# TODO (https://github.com/googleapis/gapic-generator-python/issues/2129): Update the default type for credentials. #}
+            credentials: Optional[Any] = None,
+            client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+            url_scheme: str = 'https',
+            ) -> None:
+        """Instantiate the transport.
+
+       {% if not opts.rest_numeric_enums %}
+       NOTE: This async REST transport functionality is currently in a beta
+       state (preview). We welcome your feedback via a GitHub issue in
+       this library's repository. Thank you!
+       {% endif %}
+
+        Args:
+            host ({% if service.host %}Optional[str]{% else %}str{% endif %}):
+                {{ ' ' }}The hostname to connect to {% if service.host %}(default: '{{ service.host }}'){% endif %}.
+            {# TODO (https://github.com/googleapis/gapic-generator-python/issues/2129): Update the default type for credentials. #}
+            credentials (Optional[Any]): The
+                authorization credentials to attach to requests. These
+                credentials identify the application to the service; if none
+                are specified, the client will attempt to ascertain the
+                credentials from the environment.
+            client_info (google.api_core.gapic_v1.client_info.ClientInfo):
+                The client info used to send a user-agent string along with
+                API requests. If ``None``, then default info will be used.
+                Generally, you only need to set this if you are developing
+                your own client library.
+            url_scheme (str): the protocol scheme for the API endpoint.  Normally
+                "https", but for testing or local servers,
+                "http" can be specified.
+        """
+        # Run the base constructor
+        super().__init__(
+            host=host,
+            credentials=credentials,
+            client_info=client_info,
+            always_use_jwt_access=False,
+            url_scheme=url_scheme,
+            api_audience=None
+        )
+
+    @property
+    def kind(self) -> str:
+        return "rest_asyncio"
+
+{% endblock %}

gapic/templates/tests/unit/gapic/%name_%version/%sub/test_%service.py.j2

@@ -1,3 +1,5 @@
+{# 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 %}
 {% extends "_base.py.j2" %}
 
 {% block content %}
@@ -1041,9 +1043,17 @@ def test_transport_adc(transport_class):
         transport_class()
         adc.assert_called_once()
 
-{{ test_macros.transport_kind_test(service, opts) }}
-
-{{ test_macros.transport_kind_test(service, opts, is_async=True) }}
+{% set configs = [] %}
+{% for transport_name in opts.transport %}
+    {% do configs.append({'service':service, 'transport_name':transport_name, 'is_async':false}) %}
+{# TODO(#2121): Remove this condition when async rest is GA. #}
+{% if 'grpc' in transport_name or rest_async_io_enabled %}
+    {% do configs.append({'service':service, 'transport_name':transport_name + "_asyncio", 'is_async':true}) %}
+{% endif %}
+{% endfor %}
+{% for conf in configs %}
+{{ test_macros.transport_kind_test(**conf) }}
+{% endfor %}
 
 {% if 'grpc' in opts.transport %}
 def test_transport_grpc_default():

gapic/templates/tests/unit/gapic/%name_%version/%sub/test_macros.j2

@@ -1877,33 +1877,19 @@ def test_{{ method_name }}_empty_call():
         assert args[0] == {{ method.input.ident }}()
 {% endmacro %}
 
+{% macro get_credentials(is_async=False) %}
+{{-'async_anonymous_credentials()' if is_async else 'ga_credentials.AnonymousCredentials()'-}}
+{% endmacro %}
 
-{% macro transport_kind_test(service, opts, is_async=False) %}
-@pytest.mark.parametrize("transport_name", [
-    {% if is_async %}
-    {% if "grpc" in opts.transport %}
-    "grpc_asyncio",
-    {% endif %}
-    {% else %}{# if not is_async #}
-    {% if "grpc" in opts.transport%}
-    "grpc",
-    {% endif %}
-    {% if "rest" in opts.transport %}
-    "rest",
-    {% endif %}
-    {% endif %}{# is_async #}
-])
-{% if is_async %}
-@pytest.mark.asyncio
-async def test_transport_kind_async(transport_name):
-    transport = {{ service.async_client_name }}.get_transport_class(transport_name)(
-        credentials=async_anonymous_credentials(),
-    )
-{% else %}
-def test_transport_kind(transport_name):
-    transport = {{ service.client_name }}.get_transport_class(transport_name)(
-        credentials=ga_credentials.AnonymousCredentials(),
+{% macro get_client(service, is_async) %}
+{{-service.async_client_name if is_async else service.client_name-}}
+{% endmacro %}
+
+{% macro transport_kind_test(service, transport_name, is_async) %}
+def test_transport_kind_{{transport_name}}():
+    transport = {{ get_client(service, is_async) }}.get_transport_class("{{transport_name}}")(
+        credentials={{get_credentials(is_async)}}
     )
-{% endif %}
-    assert transport.kind == transport_name
-{% endmacro %}
+    assert transport.kind == "{{ transport_name }}"
+
+{% endmacro %}

noxfile.py

@@ -174,12 +174,31 @@ def fragment(session, use_ads_templates=False):
 def fragment_alternative_templates(session):
     fragment(session, use_ads_templates=True)
 
+# `_add_python_settings` consumes a path to a temporary directory (str) i.e. tmp_dir and 
+# python settings i.e. python_settings (Dict) and modifies the service yaml within 
+# tmp_dir to include python settings. The primary purpose of this function is to modify 
+# the service yaml and include `rest_async_io_enabled=True` to test the async rest
+# optional feature.
+def _add_python_settings(tmp_dir, python_settings):
+    return f"""
+import yaml
+from pathlib import Path
+temp_file_path = Path(f"{tmp_dir}/showcase_v1beta1.yaml")
+with temp_file_path.open('r') as file:
+    data = yaml.safe_load(file)
+    data['publishing']['library_settings'] = {python_settings}
+
+with temp_file_path.open('w') as file:
+    yaml.safe_dump(data, file, default_flow_style=False, sort_keys=False)
+"""
 
+# TODO(https://github.com/googleapis/gapic-generator-python/issues/2121): `rest_async_io_enabled` must be removed once async rest is GA.
 @contextmanager
 def showcase_library(
     session, templates="DEFAULT", other_opts: typing.Iterable[str] = (),
     include_service_yaml=True,
     retry_config=True,
+    rest_async_io_enabled=False
 ):
     """Install the generated library into the session for showcase tests."""
 
@@ -220,6 +239,25 @@ def showcase_library(
                 external=True,
                 silent=True,
             )
+            # TODO(https://github.com/googleapis/gapic-generator-python/issues/2121): The section below updates the showcase service yaml
+            # to test experimental async rest transport. It must be removed once support for async rest is GA.
+            if rest_async_io_enabled:
+                # Install pyYAML for yaml.
+                session.install("pyYAML")
+
+                python_settings = [
+                    {
+                        'version': 'google.showcase.v1beta1',
+                        'python_settings': {
+                            'experimental_features': {
+                                'rest_async_io_enabled': True
+                            }
+                        }
+                    }
+                ]
+                update_service_yaml = _add_python_settings(tmp_dir, python_settings)
+                session.run("python", "-c" f"{update_service_yaml}")
+            # END TODO section to remove.
         if retry_config:
             session.run(
                 "curl",
@@ -392,6 +430,19 @@ def showcase_unit(
         run_showcase_unit_tests(session)
 
 
+# TODO: `showcase_unit_w_rest_async` nox session runs showcase unit tests with the
+# experimental async rest transport and must be removed once support for async rest is GA.
+# See related issue: https://github.com/googleapis/gapic-generator-python/issues/2121.
+@nox.session(python=ALL_PYTHON)
+def showcase_unit_w_rest_async(
+    session, templates="DEFAULT", other_opts: typing.Iterable[str] = (),
+):
+    """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)
+        run_showcase_unit_tests(session)
+
+
 @nox.session(python=ALL_PYTHON)
 def showcase_unit_alternative_templates(session):
     with showcase_library(

tests/integration/goldens/asset/tests/unit/gapic/asset_v1/test_asset_service.py

@@ -16405,26 +16405,25 @@ def test_transport_adc(transport_class):
         transport_class()
         adc.assert_called_once()
 
-@pytest.mark.parametrize("transport_name", [
-    "grpc",
-    "rest",
-])
-def test_transport_kind(transport_name):
-    transport = AssetServiceClient.get_transport_class(transport_name)(
-        credentials=ga_credentials.AnonymousCredentials(),
+def test_transport_kind_grpc():
+    transport = AssetServiceClient.get_transport_class("grpc")(
+        credentials=ga_credentials.AnonymousCredentials()
     )
-    assert transport.kind == transport_name
+    assert transport.kind == "grpc"
 
 
-@pytest.mark.parametrize("transport_name", [
-    "grpc_asyncio",
-])
-@pytest.mark.asyncio
-async def test_transport_kind_async(transport_name):
-    transport = AssetServiceAsyncClient.get_transport_class(transport_name)(
-        credentials=async_anonymous_credentials(),
+def test_transport_kind_grpc_asyncio():
+    transport = AssetServiceAsyncClient.get_transport_class("grpc_asyncio")(
+        credentials=async_anonymous_credentials()
+    )
+    assert transport.kind == "grpc_asyncio"
+
+
+def test_transport_kind_rest():
+    transport = AssetServiceClient.get_transport_class("rest")(
+        credentials=ga_credentials.AnonymousCredentials()
     )
-    assert transport.kind == transport_name
+    assert transport.kind == "rest"
 
 
 def test_transport_grpc_default():

tests/integration/goldens/credentials/tests/unit/gapic/credentials_v1/test_iam_credentials.py

@@ -3490,26 +3490,25 @@ def test_transport_adc(transport_class):
         transport_class()
         adc.assert_called_once()
 
-@pytest.mark.parametrize("transport_name", [
-    "grpc",
-    "rest",
-])
-def test_transport_kind(transport_name):
-    transport = IAMCredentialsClient.get_transport_class(transport_name)(
-        credentials=ga_credentials.AnonymousCredentials(),
+def test_transport_kind_grpc():
+    transport = IAMCredentialsClient.get_transport_class("grpc")(
+        credentials=ga_credentials.AnonymousCredentials()
     )
-    assert transport.kind == transport_name
+    assert transport.kind == "grpc"
 
 
-@pytest.mark.parametrize("transport_name", [
-    "grpc_asyncio",
-])
-@pytest.mark.asyncio
-async def test_transport_kind_async(transport_name):
-    transport = IAMCredentialsAsyncClient.get_transport_class(transport_name)(
-        credentials=async_anonymous_credentials(),
+def test_transport_kind_grpc_asyncio():
+    transport = IAMCredentialsAsyncClient.get_transport_class("grpc_asyncio")(
+        credentials=async_anonymous_credentials()
+    )
+    assert transport.kind == "grpc_asyncio"
+
+
+def test_transport_kind_rest():
+    transport = IAMCredentialsClient.get_transport_class("rest")(
+        credentials=ga_credentials.AnonymousCredentials()
     )
-    assert transport.kind == transport_name
+    assert transport.kind == "rest"
 
 
 def test_transport_grpc_default():