[gRPC] Update the code generator for Python to produce typed handlers (#8326)

* Move `namer.h` and `idl_namer.h` to `include/codegen` so they can be reused from `grpc` dirqectory.

* [gRPC] Update the Python generator to produce typed handlers and Python stubs if requested.

* [gRPC] Document the newly added compiler flags.

tests/PythonTest.sh

@@ -27,6 +27,7 @@ ${test_dir}/../flatc -p -o ${gen_code_path} -I include_test monster_test.fbs --g
 ${test_dir}/../flatc -p -o ${gen_code_path} -I include_test monster_extra.fbs --gen-object-api --python-typing --gen-compare
 ${test_dir}/../flatc -p -o ${gen_code_path} -I include_test arrays_test.fbs --gen-object-api --python-typing
 ${test_dir}/../flatc -p -o ${gen_code_path} -I include_test nested_union_test.fbs --gen-object-api --python-typing
+${test_dir}/../flatc -p -o ${gen_code_path} -I include_test service_test.fbs --grpc --grpc-python-typed-handlers --python-typing --no-python-gen-numpy --gen-onefile
 
 # Syntax: run_tests <interpreter> <benchmark vtable dedupes>
 #                   <benchmark read count> <benchmark build count>

tests/service_test.fbs

@@ -0,0 +1,11 @@
+namespace example;
+
+table HelloRequest {}
+table HelloResponse {}
+
+rpc_service HelloService {
+  Hello(HelloRequest):HelloResponse;
+  StreamClient(HelloRequest):HelloResponse (streaming: "client");
+  StreamServer(HelloRequest):HelloResponse (streaming: "server");
+  Stream(HelloRequest):HelloResponse (streaming: "bidi");
+}

tests/service_test_generated.py

@@ -0,0 +1,58 @@
+# automatically generated by the FlatBuffers compiler, do not modify
+
+# namespace: example
+
+import flatbuffers
+from typing import Any
+class HelloRequest(object):
+    __slots__ = ['_tab']
+
+    @classmethod
+    def GetRootAs(cls, buf, offset: int = 0):
+        n = flatbuffers.encode.Get(flatbuffers.packer.uoffset, buf, offset)
+        x = HelloRequest()
+        x.Init(buf, n + offset)
+        return x
+
+    @classmethod
+    def GetRootAsHelloRequest(cls, buf, offset=0):
+        """This method is deprecated. Please switch to GetRootAs."""
+        return cls.GetRootAs(buf, offset)
+    # HelloRequest
+    def Init(self, buf: bytes, pos: int):
+        self._tab = flatbuffers.table.Table(buf, pos)
+
+def HelloRequestStart(builder: flatbuffers.Builder):
+    builder.StartObject(0)
+
+def HelloRequestEnd(builder: flatbuffers.Builder) -> int:
+    return builder.EndObject()
+
+
+
+class HelloResponse(object):
+    __slots__ = ['_tab']
+
+    @classmethod
+    def GetRootAs(cls, buf, offset: int = 0):
+        n = flatbuffers.encode.Get(flatbuffers.packer.uoffset, buf, offset)
+        x = HelloResponse()
+        x.Init(buf, n + offset)
+        return x
+
+    @classmethod
+    def GetRootAsHelloResponse(cls, buf, offset=0):
+        """This method is deprecated. Please switch to GetRootAs."""
+        return cls.GetRootAs(buf, offset)
+    # HelloResponse
+    def Init(self, buf: bytes, pos: int):
+        self._tab = flatbuffers.table.Table(buf, pos)
+
+def HelloResponseStart(builder: flatbuffers.Builder):
+    builder.StartObject(0)
+
+def HelloResponseEnd(builder: flatbuffers.Builder) -> int:
+    return builder.EndObject()
+
+
+

tests/service_test_generated.pyi

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+import flatbuffers
+
+import flatbuffers
+import typing
+
+uoffset: typing.TypeAlias = flatbuffers.number_types.UOffsetTFlags.py_type
+
+class HelloRequest(object):
+  @classmethod
+  def GetRootAs(cls, buf: bytes, offset: int) -> HelloRequest: ...
+  @classmethod
+  def GetRootAsHelloRequest(cls, buf: bytes, offset: int) -> HelloRequest: ...
+  def Init(self, buf: bytes, pos: int) -> None: ...
+def HelloRequestStart(builder: flatbuffers.Builder) -> None: ...
+def HelloRequestEnd(builder: flatbuffers.Builder) -> uoffset: ...
+class HelloResponse(object):
+  @classmethod
+  def GetRootAs(cls, buf: bytes, offset: int) -> HelloResponse: ...
+  @classmethod
+  def GetRootAsHelloResponse(cls, buf: bytes, offset: int) -> HelloResponse: ...
+  def Init(self, buf: bytes, pos: int) -> None: ...
+def HelloResponseStart(builder: flatbuffers.Builder) -> None: ...
+def HelloResponseEnd(builder: flatbuffers.Builder) -> uoffset: ...
+

tests/service_test_grpc.fb.py

@@ -0,0 +1,97 @@
+# Generated by the gRPC FlatBuffers compiler. DO NOT EDIT!
+
+import flatbuffers
+import grpc
+
+from service_test_generated import HelloRequest, HelloResponse
+
+
+def _serialize_to_bytes(table):
+  buf = table._tab.Bytes
+  n = flatbuffers.encode.Get(flatbuffers.packer.uoffset, buf, 0)
+  if table._tab.Pos != n:
+    raise ValueError('must be a top-level table')
+  return bytes(buf)
+
+
+class HelloServiceStub(object):
+  '''Interface exported by the server.'''
+
+  def __init__(self, channel):
+    '''Constructor.
+
+    Args:
+      channel: A grpc.Channel.
+    '''
+
+    self.Hello = channel.unary_unary(
+      method='/example.HelloService/Hello',
+      request_serializer=_serialize_to_bytes,
+      response_deserializer=HelloResponse.GetRootAs)
+
+    self.StreamClient = channel.stream_unary(
+      method='/example.HelloService/StreamClient',
+      request_serializer=_serialize_to_bytes,
+      response_deserializer=HelloResponse.GetRootAs)
+
+    self.StreamServer = channel.unary_stream(
+      method='/example.HelloService/StreamServer',
+      request_serializer=_serialize_to_bytes,
+      response_deserializer=HelloResponse.GetRootAs)
+
+    self.Stream = channel.stream_stream(
+      method='/example.HelloService/Stream',
+      request_serializer=_serialize_to_bytes,
+      response_deserializer=HelloResponse.GetRootAs)
+
+
+class HelloServiceServicer(object):
+  '''Interface exported by the server.'''
+
+  def Hello(self, request, context):
+    context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+    context.set_details('Method not implemented!')
+    raise NotImplementedError('Method not implemented!')
+
+  def StreamClient(self, request_iterator, context):
+    context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+    context.set_details('Method not implemented!')
+    raise NotImplementedError('Method not implemented!')
+
+  def StreamServer(self, request, context):
+    context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+    context.set_details('Method not implemented!')
+    raise NotImplementedError('Method not implemented!')
+
+  def Stream(self, request_iterator, context):
+    context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+    context.set_details('Method not implemented!')
+    raise NotImplementedError('Method not implemented!')
+
+
+def add_HelloServiceServicer_to_server(servicer, server):
+  rpc_method_handlers = {
+    'Hello': grpc.unary_unary_rpc_method_handler(
+      servicer.Hello,
+      request_deserializer=HelloRequest.GetRootAs,
+      response_serializer=_serialize_to_bytes),
+    'StreamClient': grpc.stream_unary_rpc_method_handler(
+      servicer.StreamClient,
+      request_deserializer=HelloRequest.GetRootAs,
+      response_serializer=_serialize_to_bytes),
+    'StreamServer': grpc.unary_stream_rpc_method_handler(
+      servicer.StreamServer,
+      request_deserializer=HelloRequest.GetRootAs,
+      response_serializer=_serialize_to_bytes),
+    'Stream': grpc.stream_stream_rpc_method_handler(
+      servicer.Stream,
+      request_deserializer=HelloRequest.GetRootAs,
+      response_serializer=_serialize_to_bytes),
+  }
+
+  generic_handler = grpc.method_handlers_generic_handler(
+    'example.HelloService', rpc_method_handlers)
+
+  server.add_generic_rpc_handlers((generic_handler,))
+
+

tests/service_test_grpc.fb.pyi

@@ -0,0 +1,27 @@
+# Generated by the gRPC FlatBuffers compiler. DO NOT EDIT!
+
+from __future__ import annotations
+
+import grpc
+import typing
+
+from service_test_generated import HelloRequest, HelloResponse
+
+
+class HelloServiceStub(object):
+  def __init__(self, channel: grpc.Channel) -> None: ...
+  def Hello(self, request: HelloRequest) -> HelloResponse: ...
+  def StreamClient(self, request_iterator: typing.Iterator[HelloRequest]) -> HelloResponse: ...
+  def StreamServer(self, request: HelloRequest) -> typing.Iterator[HelloResponse]: ...
+  def Stream(self, request_iterator: typing.Iterator[HelloRequest]) -> typing.Iterator[HelloResponse]: ...
+
+
+class HelloServiceServicer(object):
+  def Hello(self, request: HelloRequest, context: grpc.ServicerContext) -> HelloResponse: ...
+  def StreamClient(self, request_iterator: typing.Iterator[HelloRequest], context: grpc.ServicerContext) -> HelloResponse: ...
+  def StreamServer(self, request: HelloRequest, context: grpc.ServicerContext) -> typing.Iterator[HelloResponse]: ...
+  def Stream(self, request_iterator: typing.Iterator[HelloRequest], context: grpc.ServicerContext) -> typing.Iterator[HelloResponse]: ...
+
+
+def add_HelloServiceServicer_to_server(servicer: HelloServiceServicer, server: grpc.Server) -> None: ...
+