Pluggable templates (#20)

Author: lukesneeringer

packages/gapic-generator/gapic/cli/generate.py

@@ -32,9 +32,14 @@
 @click.option('--output', type=click.File('wb'), default=sys.stdout.buffer,
               help='Where to output the `CodeGeneratorResponse`. '
                    'Defaults to stdout.')
+@click.option('--templates', type=click.Path(exists=True), default=None,
+              help='Which templates to use to generate a library. '
+                   'Defaults to the templates included in gapic-generator, '
+                   'which generate client libraries for Python 3.4 and up.')
 def generate(
         request: typing.BinaryIO,
-        output: typing.BinaryIO) -> None:
+        output: typing.BinaryIO,
+        templates: str = None) -> None:
     """Generate a full API client description."""
 
     # Load the protobuf CodeGeneratorRequest.
@@ -57,7 +62,7 @@ def generate(
     # Translate into a protobuf CodeGeneratorResponse; this reads the
     # individual templates and renders them.
     # If there are issues, error out appropriately.
-    res = generator.Generator(api_schema=api_schema).get_response()
+    res = generator.Generator(api_schema, templates=templates).get_response()
 
     # Output the serialized response.
     output.write(res.SerializeToString())

packages/gapic-generator/gapic/generator/generator.py

@@ -12,13 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import io
 import os
 from typing import Any, Iterable, Mapping, Sequence
 
 import jinja2
 
-from google.protobuf.compiler.plugin_pb2 import CodeGeneratorRequest
 from google.protobuf.compiler.plugin_pb2 import CodeGeneratorResponse
 
 from gapic import utils
@@ -30,25 +28,32 @@
 class Generator:
     """A protoc code generator for client libraries.
 
-    This class receives a :class:`~.plugin_pb2.CodeGeneratorRequest` (as per
-    the protoc plugin contract), and provides an interface for getting
-    a :class:`~.plugin_pb2.CodeGeneratorResponse`.
-
-    That request with one or more protocol buffers which collectively
-    describe an API.
+    This class receives a :class:`~.api.API`, a representation of the API
+    schema, and provides an interface for getting a
+    :class:`~.plugin_pb2.CodeGeneratorResponse` (which it does through
+    rendering templates).
 
     Args:
-        request (CodeGeneratorRequest): A request protocol buffer as provided
-            by protoc. See ``plugin.proto``.
+        api_schema (~.API): An API schema object, which is sent to every
+            template as the ``api`` variable.
+        templates (str): Optional. Path to the templates to be
+            rendered. If this is not provided, the templates included with
+            this application are used.
     """
-    def __init__(self, api_schema: api.API) -> None:
+    def __init__(self, api_schema: api.API, *,
+                 templates: str = None) -> None:
         self._api = api_schema
 
+        # If explicit templates were not provided, use our default.
+        if not templates:
+            templates = os.path.join(
+                os.path.realpath(os.path.dirname(__file__)),
+                '..', 'templates',
+            )
+
         # Create the jinja environment with which to render templates.
         self._env = jinja2.Environment(
-            loader=loader.TemplateLoader(
-                searchpath=os.path.join(_dirname, '..', 'templates'),
-            ),
+            loader=loader.TemplateLoader(searchpath=templates),
             undefined=jinja2.StrictUndefined,
         )
 
@@ -173,9 +178,6 @@ def _get_output_filename(
         return filename
 
 
-_dirname = os.path.realpath(os.path.dirname(__file__))
-
-
 __all__ = (
     'Generator',
 )

packages/gapic-generator/tests/unit/generator/test_generator.py

@@ -41,6 +41,14 @@ def test_constructor():
     assert 'wrap' in g._env.filters
 
 
+def test_custom_template_directory():
+    # Create a generator.
+    g = generator.Generator(api_schema=make_api(), templates='/templates/')
+
+    # Assert that the Jinja loader will pull from the correct location.
+    assert g._env.loader.searchpath == ['/templates/']
+
+
 def test_get_response():
     # Create a generator with mock data.
     #