feat: add rest transport generation for clients with optional flag

gapic/ads-templates/%namespace/%name/%version/__init__.py.j2

@@ -20,6 +20,7 @@ _lazy_type_to_package_map = {
     '{{ enum.name }}': '{{ enum.ident.package|join('.') }}.types.{{enum.ident.module }}',
 {%- endfor %}
 
+    {# TODO(yonmg): add rest transport service once I know what this is #}
     # Client classes and transports  
 {%- for service in api.services.values() %}
     '{{ service.client_name }}': '{{ service.meta.address.package|join('.') }}.services.{{ service.meta.address.module }}',

gapic/ads-templates/%namespace/%name/__init__.py.j2

@@ -20,6 +20,7 @@ _lazy_type_to_package_map = {
     '{{ enum.name }}': '{{ enum.ident.package|join('.') }}.types.{{enum.ident.module }}',
 {%- endfor %}
 
+    {# TODO(yonmg): add rest transport service once I know what this is #}
     # Client classes and transports  
 {%- for service in api.services.values() %}
     '{{ service.client_name }}': '{{ service.meta.address.package|join('.') }}.services.{{ service.meta.address.module }}',

gapic/generator/generator.py

@@ -274,6 +274,10 @@ def _render_template(
                 if (
                         skip_subpackages
                         and service.meta.address.subpackage != api_schema.subpackage_view
+                        or
+                        'grpc' in template_name and 'grpc' not in opts.transport
+                        or
+                        'rest' in template_name and 'rest' not in opts.transport
                 ):
                     continue
 

gapic/schema/wrappers.py

@@ -980,6 +980,10 @@ def grpc_transport_name(self):
     def grpc_asyncio_transport_name(self):
         return self.name + "GrpcAsyncIOTransport"
 
+    @property
+    def rest_transport_name(self):
+        return self.name + "RestTransport"
+
     @property
     def has_lro(self) -> bool:
         """Return whether the service has a long-running method."""

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

@@ -30,6 +30,7 @@ from .transports.grpc_asyncio import {{ service.grpc_asyncio_transport_name }}
 from .client import {{ service.client_name }}
 
 
+{# TODO(yonmg): handle rest transport async client interaction #}
 class {{ service.async_client_name }}:
     """{{ service.meta.doc|rst(width=72, indent=4) }}"""
 

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

@@ -30,8 +30,13 @@ from google.iam.v1 import policy_pb2 as policy  # type: ignore
 {% endif %}
 {% endfilter %}
 from .transports.base import {{ service.name }}Transport, DEFAULT_CLIENT_INFO
-from .transports.grpc import {{ service.grpc_transport_name }}
-from .transports.grpc_asyncio import {{ service.grpc_asyncio_transport_name }}
+{%- if 'grpc' in opts.transport %}
+from .grpc import {{ service.name }}GrpcTransport
+from .grpc_asyncio import {{ service.name }}GrpcAsyncIOTransport
+{%- endif %}
+{%- if 'rest' in opts.transport %}
+from .rest import {{ service.name }}RestTransport
+{%- endif %}
 
 
 class {{ service.client_name }}Meta(type):
@@ -42,8 +47,13 @@ class {{ service.client_name }}Meta(type):
     objects.
     """
     _transport_registry = OrderedDict()  # type: Dict[str, Type[{{ service.name }}Transport]]
-    _transport_registry['grpc'] = {{ service.grpc_transport_name }}
-    _transport_registry['grpc_asyncio'] = {{ service.grpc_asyncio_transport_name }}
+    {%- if 'grpc' in opts.transport %}
+    _transport_registry['grpc'] = {{ service.name }}GrpcTransport
+    _transport_registry['grpc_asyncio'] = {{ service.name }}GrpcAsyncIOTransport
+    {%- endif %}
+    {%- if 'rest' in opts.transport %}
+    _transport_registry['rest'] = {{ service.name }}RestTransport
+    {%- endif %}
 
     def get_transport_class(cls,
             label: str = None,

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

@@ -5,19 +5,34 @@ from collections import OrderedDict
 from typing import Dict, Type
 
 from .base import {{ service.name }}Transport
+{%- if 'grpc' in opts.transport %}
 from .grpc import {{ service.name }}GrpcTransport
 from .grpc_asyncio import {{ service.name }}GrpcAsyncIOTransport
+{%- endif %}
+{%- if 'rest' in opts.transport %}
+from .rest import {{ service.name }}RestTransport
+{%- endif %}
+
 
 
 # Compile a registry of transports.
 _transport_registry = OrderedDict()  # type: Dict[str, Type[{{ service.name }}Transport]]
+{%- if 'grpc' in opts.transport %}
 _transport_registry['grpc'] = {{ service.name }}GrpcTransport
 _transport_registry['grpc_asyncio'] = {{ service.name }}GrpcAsyncIOTransport
-
+{%- endif %}
+{%- if 'rest' in opts.transport %}
+_transport_registry['rest'] = {{ service.name }}RestTransport
+{%- endif %}
 
 __all__ = (
     '{{ service.name }}Transport',
+    {%- if 'grpc' in opts.transport %}
     '{{ service.name }}GrpcTransport',
     '{{ service.name }}GrpcAsyncIOTransport',
+    {%- endif %}
+    {%- if 'rest' in opts.transport %}
+    '{{ service.name }}RestTransport',
+    {%- endif %}
 )
 {% endblock %}

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

@@ -172,7 +172,7 @@ class {{ service.name }}GrpcTransport({{ service.name }}Transport):
                        **kwargs) -> grpc.Channel:
         """Create and return a gRPC channel object.
         Args:
-            address (Optionsl[str]): The host for the channel to use.
+            address (Optional[str]): The host for the channel to use.
             credentials (Optional[~.Credentials]): The
                 authorization credentials to attach to requests. These
                 credentials identify this application to the service. If

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

@@ -0,0 +1,200 @@
+{% extends '_base.py.j2' %}
+
+{% block content %}
+import warnings
+from typing import Callable, Dict, Optional, Sequence, Tuple
+
+{% if service.has_lro %}
+from google.api_core import operations_v1
+{%- endif %}
+from google.api_core import gapic_v1       # type: ignore
+from google import auth                    # type: ignore
+from google.auth import credentials        # type: ignore
+from google.auth.transport.grpc import SslCredentials  # type: ignore
+
+import grpc  # type: ignore
+
+from google.auth.transport.requests import AuthorizedSession
+
+{# TODO: re-add python_import/ python_modules from removed diff/current grpc template code #}
+{% filter sort_lines -%}
+{% for method in service.methods.values() -%}
+{{ method.input.ident.python_import }}
+{{ method.output.ident.python_import }}
+{% endfor -%}
+{% if opts.add_iam_methods %}
+from google.iam.v1 import iam_policy_pb2 as iam_policy  # type: ignore
+from google.iam.v1 import policy_pb2 as policy  # type: ignore
+{% endif %}
+{% endfilter %}
+
+from .base import {{ service.name }}Transport, DEFAULT_CLIENT_INFO
+
+
+class {{ service.name }}RestTransport({{ service.name }}Transport):
+    """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 = 'compute.googleapis.com',
+            credentials: credentials.Credentials = None,
+            credentials_file: str = None,
+            scopes: Sequence[str] = None,
+            ssl_channel_credentials: grpc.ChannelCredentials = None,
+            quota_project_id: Optional[str] = None,
+            client_info: gapic_v1.client_info.ClientInfo = DEFAULT_CLIENT_INFO,
+            ) -> None:
+        """Instantiate the transport.
+
+        Args:
+            host ({% if service.host %}Optional[str]{% else %}str{% endif %}):
+                {{- ' ' }}The hostname to connect to.
+            credentials (Optional[google.auth.credentials.Credentials]): 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.
+
+            credentials_file (Optional[str]): A file with credentials that can
+                be loaded with :func:`google.auth.load_credentials_from_file`.
+                This argument is ignored if ``channel`` is provided.
+            scopes (Optional(Sequence[str])): A list of scopes. This argument is
+                ignored if ``channel`` is provided.
+            ssl_channel_credentials (grpc.ChannelCredentials): SSL credentials
+                for grpc channel. It is ignored if ``channel`` is provided.
+            quota_project_id (Optional[str]): An optional project to use for billing
+                and quota.
+            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're developing	
+                your own client library.
+        """
+        super().__init__(host=host, credentials=credentials)
+        self._session = AuthorizedSession(self._credentials)
+    {%- if service.has_lro %}
+
+    @property
+    def operations_client(self) -> operations_v1.OperationsClient:
+        """Create the client designed to process long-running operations.
+
+        This property caches on the instance; repeated calls return the same
+        client.
+        """
+        # Sanity check: Only create a new client if we do not already have one.
+        if 'operations_client' not in self.__dict__:
+            from google.api_core import grpc_helpers
+            self.__dict__['operations_client'] = operations_v1.OperationsClient(
+                grpc_helpers.create_channel(
+                    self._host,
+                    credentials=self._credentials,
+                    scopes=self.AUTH_SCOPES,
+                )
+            )
+
+        # Return the client from cache.
+        return self.__dict__['operations_client']
+    {%- endif %}
+
+
+    {%- for method in service.methods.values() %}
+    {# TODO(yonmg): consider using enums #}
+        {%- set ns = namespace(http=None) %}
+        {%- for option in method.options.ListFields() %}
+            {%- if option[0].name == 'http' %}
+                {%- set ns.http = option[1] %}
+            {%- endif %}
+        {%- endfor %}
+
+        {%- if ns.http %}
+
+
+    def {{ method.name|snake_case }}(self,
+            request: {{ method.input.ident }}, *,
+            metadata: Sequence[Tuple[str, str]] = (),
+            ) -> {{ method.output.ident }}:
+        r"""Call the {{- ' ' -}}
+        {{ (method.name|snake_case).replace('_',' ')|wrap(
+                width=70, offset=45, indent=8) }}
+        {{- ' ' -}} method over HTTP.
+
+        Args:
+            request (~.{{ method.input.ident }}):
+                The request object.
+                {{ method.input.meta.doc|rst(width=72, indent=16) }}
+            metadata (Sequence[Tuple[str, str]]): Strings which should be
+                sent along with the request as metadata.
+        {%- if not method.void %}
+
+        Returns:
+            ~.{{ method.output.ident }}:
+                {{ method.output.meta.doc|rst(width=72, indent=16) }}
+        {%- endif %}
+        """
+
+        # Check which http method to use
+        {%- if ns.http.get != '' %}
+            {%- set ns.httpMethod = {'method':'get','url':ns.http.get} %}
+        {%- elif ns.http.put != '' %}
+            {%- set ns.httpMethod = {'method':'put','url':ns.http.put} %}
+        {%- elif ns.http.post != '' %}
+            {%- set ns.httpMethod = {'method':'post','url':ns.http.post} %}
+        {%- elif ns.http.delete != '' %}
+            {%- set ns.httpMethod = {'method':'delete','url':ns.http.delete} %}
+        {%- elif ns.http.patch != '' %}
+            {%- set ns.httpMethod = {'method':'patch','url':ns.http.patch} %}
+        {%- elif ns.http.custom != '' %}
+            {%- set ns.httpMethod = {'method':'custom','url':ns.http.custom} %}
+        {%- else %}
+            {%- set ns.httpMethod = None %}
+        {%- endif %}
+
+        {%- if ns.http.body != '' %}
+        # Jsonify the input
+        data = {{ method.output.ident }}.to_json(
+            {%- if ns.http.body == '*' %}
+            request
+            {%- else %}
+            request.body
+            {%- endif %}
+        )
+        {%- endif %}
+
+        {# TODO(yonmg): Write helper method for handling grpc transcoding url #}
+        # TODO(yonmg): need to handle grpc transcoding and parse url correctly
+        #              current impl assumes simpler version of grpc transcoding
+        # Send the request
+        url = 'https://{host}{{ ns.httpMethod['url'] }}'.format(
+            host=self._host,
+            {%- for field in method.input.fields.keys() %}
+            {{ field }}=request.{{ field }},
+            {%- endfor %}
+        )
+        {% if not method.void %}response = {% endif %}self._session.{{ ns.httpMethod['method'] }}(
+            url,
+            {%- if ns.http.body != '' %}
+            json=data,
+            {%- endif %}
+        )
+        {%- if not method.void %}
+        {%- endif %}
+
+        # Return the response
+        return {{ method.output.ident }}.from_json(response.content)
+        {%- else %}
+    # No http annotation found for method {{ method.name|snake_case }}()  
+        {%- endif %}
+    {%- endfor %}
+
+
+__all__ = (
+    '{{ service.name }}RestTransport',
+)
+{% endblock %}

gapic/utils/options.py

@@ -14,7 +14,7 @@
 
 from collections import defaultdict
 from os import path
-from typing import Any, DefaultDict, Dict, FrozenSet, List, Optional, Tuple
+from typing import Any, DefaultDict, Dict, FrozenSet, List, Optional, Tuple, Set
 
 import dataclasses
 import json
@@ -40,6 +40,8 @@ class Options:
     lazy_import: bool = False
     old_naming: bool = False
     add_iam_methods: bool = False
+    # TODO(yonmg): should there be an enum for transport type?
+    transport: List[str] = None
 
     # Class constants
     PYTHON_GAPIC_PREFIX: str = 'python-gapic-'
@@ -49,6 +51,7 @@ class Options:
         'samples',              # output dir
         'lazy-import',          # requires >= 3.7
         'add-iam-methods',      # microgenerator implementation for `reroute_to_grpc_interface`
+        'transport',            # transport type (i.e. grpc, rest, custom.[something], etc?)
     ))
 
     @classmethod
@@ -86,7 +89,7 @@ def build(cls, opt_string: str) -> 'Options':
             # Throw away other options not meant for us.
             if not opt.startswith(cls.PYTHON_GAPIC_PREFIX):
                 continue
-
+            
             # Set the option, using a key with the "python-gapic-" prefix
             # stripped.
             #
@@ -121,6 +124,7 @@ def tweak_path(p):
 
         # Build the options instance.
         sample_paths = opts.pop('samples', [])
+
         answer = Options(
             name=opts.pop('name', ['']).pop(),
             namespace=tuple(opts.pop('namespace', [])),
@@ -134,6 +138,7 @@ def tweak_path(p):
             lazy_import=bool(opts.pop('lazy-import', False)),
             old_naming=bool(opts.pop('old-naming', False)),
             add_iam_methods=bool(opts.pop('add-iam-methods', False)),
+            transport=opts.pop('transport', ['grpc'])[0].split('+')
         )
 
         # Note: if we ever need to recursively check directories for sample

tests/unit/schema/wrappers/test_service.py

@@ -59,6 +59,7 @@ def test_service_properties():
     assert service.transport_name == 'ThingDoerTransport'
     assert service.grpc_transport_name == 'ThingDoerGrpcTransport'
     assert service.grpc_asyncio_transport_name == 'ThingDoerGrpcAsyncIOTransport'
+    assert service.rest_transport_name == 'ThingDoerRestTransport'
 
 
 def test_service_host():