Implement basic async gRPC support

betterproto/templates/main.py

@@ -1,12 +1,15 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
-# source: {{ description.filename }}
+# sources: {{ ', '.join(description.files) }}
 # plugin: python-betterproto
 {% if description.enums %}import enum
 {% endif %}
 from dataclasses import dataclass
-from typing import Dict, List
+from typing import AsyncGenerator, Dict, List, Optional
 
 import betterproto
+{% if description.services %}
+import grpclib
+{% endif %}
 {% for i in description.imports %}
 
 {{ i }}
@@ -48,3 +51,36 @@ class {{ message.name }}(betterproto.Message):
 
 
 {% endfor %}
+{% for service in description.services %}
+class {{ service.name }}Stub(betterproto.ServiceStub):
+    {% for method in service.methods %}
+    async def {{ method.py_name }}(self{% if method.input_message and method.input_message.properties %}, *, {% for field in method.input_message.properties %}{{ field.name }}: {% if field.zero == "None" %}Optional[{{ field.type }}]{% else %}{{ field.type }}{% endif %} = {{ field.zero }}{% if not loop.last %}, {% endif %}{% endfor %}{% endif %}) -> {% if method.server_streaming %}AsyncGenerator[{{ method.output }}, None]{% else %}{{ method.output }}{% endif %}:
+        request = {{ method.input }}()
+        {% for field in method.input_message.properties %}
+            {% if field.field_type == 'message' %}
+        if {{ field.name }} is not None:
+            request.{{ field.name }} = {{ field.name }}
+            {% else %}
+        request.{{ field.name }} = {{ field.name }}
+            {% endif %}
+        {% endfor %}
+
+        {% if method.server_streaming %}
+        async for response in self._unary_stream(
+            "{{ method.route }}",
+            {{ method.input }},
+            {{ method.output }},
+            request,
+        ):
+            yield response
+        {% else %}
+        return await self._unary_unary(
+            "{{ method.route }}",
+            {{ method.input }},
+            {{ method.output }},
+            request,
+        )
+        {% endif %}
+
+    {% endfor %}
+{% endfor %}