Support for Golang GRPC (Experimental) (#4082)

* support for grpc golang

* refactored grpc go generator

* added grpc-go test and refactored

* refactored idl_gen_grpc.cpp

* fixed grpc generate method name

* refactored flatc and fixed line length issue

* added codec to go lib and fixed formatting issues

* fixed spacing issues

CMakeLists.txt

@@ -50,6 +50,8 @@ set(FlatBuffers_Compiler_SRCS
   grpc/src/compiler/schema_interface.h
   grpc/src/compiler/cpp_generator.h
   grpc/src/compiler/cpp_generator.cc
+  grpc/src/compiler/go_generator.h
+  grpc/src/compiler/go_generator.cc
 )
 
 set(FlatHash_SRCS

go/grpc.go

+package flatbuffers
+
+// FlatbuffersCodec implements gRPC-go Codec which is used to encode and decode messages.
+var Codec string = "flatbuffers"
+
+type FlatbuffersCodec struct{}
+
+func (FlatbuffersCodec) Marshal(v interface{}) ([]byte, error) {
+	return v.(*Builder).FinishedBytes(), nil
+}
+
+func (FlatbuffersCodec) Unmarshal(data []byte, v interface{}) error {
+	v.(flatbuffersInit).Init(data, GetUOffsetT(data))
+	return nil
+}
+
+func (FlatbuffersCodec) String() string {
+	return Codec
+}
+
+type flatbuffersInit interface {
+	Init(data []byte, i UOffsetT)
+}

grpc/src/compiler/go_generator.cc

+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation AN/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <map>
+#include <cctype>
+#include <sstream>
+
+#include "src/compiler/go_generator.h"
+
+template <class T>
+grpc::string as_string(T x) {
+	std::ostringstream out;
+	out << x;
+	return out.str();
+}
+
+namespace grpc_go_generator {
+
+// Returns string with first letter to lowerCase
+grpc::string unexportName(grpc::string s) {
+	if (s.size() <= 0)
+		return s;
+	s[0] = std::tolower(s[0]);
+	return s;
+}
+
+// Returns string with first letter to uppercase
+grpc::string exportName(grpc::string s) {
+	if (s.size() <= 0)
+		return s;
+	s[0] = std::toupper(s[0]);
+	return s;
+}
+
+// Generates imports for the service
+void GenerateImports(grpc_generator::File *file, grpc_generator::Printer *printer,
+                     std::map<grpc::string, grpc::string> vars) {
+	vars["filename"] = file->filename();
+	printer->Print("//Generated by gRPC Go plugin\n");
+	printer->Print("//If you make any local changes, they will be lost\n");
+	printer->Print(vars, "//source: $filename$\n\n");
+	printer->Print(vars, "package $Package$\n\n");
+	if (file->additional_imports() != "") {
+		printer->Print(file->additional_imports().c_str());
+		printer->Print("\n\n");
+	}
+	printer->Print("import (\n");
+	printer->Indent();
+	printer->Print(vars, "$context$ \"golang.org/x/net/context\"\n");
+	printer->Print(vars, "$grpc$ \"google.golang.org/grpc\"\n");
+	printer->Outdent();
+	printer->Print(")\n\n");
+}
+
+// Generates Server method signature source
+void GenerateServerMethodSignature(const grpc_generator::Method *method, grpc_generator::Printer *printer,
+                                   std::map<grpc::string, grpc::string> vars) {
+	vars["Method"] = exportName(method->name());
+	vars["Request"] = method->input_name();
+	vars["Response"] = (vars["CustomMethodIO"] == "") ? method->output_name() : vars["CustomMethodIO"];
+	if (method->NoStreaming()) {
+		printer->Print(vars, "$Method$($context$.Context, *$Request$) (*$Response$, error)");
+	} else if (method->ServerOnlyStreaming()) {
+		printer->Print(vars, "$Method$(*$Request$, $Service$_$Method$Server) error");
+	} else {
+		printer->Print(vars, "$Method$($Service$_$Method$Server) error");
+	}
+}
+
+void GenerateServerMethod(const grpc_generator::Method *method, grpc_generator::Printer *printer,
+                          std::map<grpc::string, grpc::string> vars) {
+	vars["Method"] = exportName(method->name());
+	vars["Request"] = method->input_name();
+	vars["Response"] = (vars["CustomMethodIO"] == "") ? method->output_name() : vars["CustomMethodIO"];
+	vars["FullMethodName"] = "/" + vars["Package"] + "." + vars["Service"] + "/" + vars["Method"];
+	vars["Handler"] = "_" + vars["Service"] + "_" + vars["Method"] + "_Handler";
+	if (method->NoStreaming()) {
+		printer->Print(vars, "func $Handler$(srv interface{}, ctx $context$.Context,\n\tdec func(interface{}) error, interceptor $grpc$.UnaryServerInterceptor) (interface{}, error) {\n");
+		printer->Indent();
+		printer->Print(vars, "in := new($Request$)\n");
+		printer->Print("if err := dec(in); err != nil { return nil, err }\n");
+		printer->Print(vars, "if interceptor == nil { return srv.($Service$Server).$Method$(ctx, in) }\n");
+		printer->Print(vars, "info := &$grpc$.UnaryServerInfo{\n");
+		printer->Indent();
+		printer->Print("Server: srv,\n");
+		printer->Print(vars, "FullMethod: \"$FullMethodName$\",\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+		printer->Print(vars, "handler := func(ctx $context$.Context, req interface{}) (interface{}, error) {\n");
+		printer->Indent();
+		printer->Print(vars, "return srv.($Service$Server).$Method$(ctx, req.(* $Request$))\n");
+		printer->Outdent();
+		printer->Print("}\n");
+		printer->Print("return interceptor(ctx, in, info, handler)\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+		return;
+	}
+	vars["StreamType"] = vars["ServiceUnexported"] + vars["Method"] + "Server";
+	printer->Print(vars, "func $Handler$(srv interface{}, stream $grpc$.ServerStream) error {\n");
+	printer->Indent();
+	if (method->ServerOnlyStreaming()) {
+		printer->Print(vars, "m := new($Request$)\n");
+		printer->Print(vars, "if err := stream.RecvMsg(m); err != nil { return err }\n");
+		printer->Print(vars, "return srv.($Service$Server).$Method$(m, &$StreamType${stream})\n");
+	} else {
+		printer->Print(vars, "return srv.($Service$Server).$Method$(&$StreamType${stream})\n");
+	}
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	bool genSend = method->BidiStreaming() || method->ServerOnlyStreaming();
+	bool genRecv = method->BidiStreaming() || method->ClientOnlyStreaming();
+	bool genSendAndClose = method->ClientOnlyStreaming();
+
+	printer->Print(vars, "type $Service$_$Method$Server interface { \n");
+	printer->Indent();
+	if (genSend) {
+		printer->Print(vars, "Send(* $Response$) error\n");
+	}
+	if (genRecv) {
+		printer->Print(vars, "Recv() (* $Request$, error)\n");
+	}
+	if (genSendAndClose) {
+		printer->Print(vars, "SendAndClose(* $Response$) error\n");
+	}
+	printer->Print(vars, "$grpc$.ServerStream\n");
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	printer->Print(vars, "type $StreamType$ struct {\n");
+	printer->Indent();
+	printer->Print(vars, "$grpc$.ServerStream\n");
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	if (genSend) {
+		printer->Print(vars, "func (x *$StreamType$) Send(m *$Response$) error {\n");
+		printer->Indent();
+		printer->Print("return x.ServerStream.SendMsg(m)\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+	}
+	if (genRecv) {
+		printer->Print(vars, "func (x *$StreamType$) Recv() (*$Request$, error) {\n");
+		printer->Indent();
+		printer->Print(vars, "m := new($Request$)\n");
+		printer->Print("if err := x.ServerStream.RecvMsg(m); err != nil { return nil, err }\n");
+		printer->Print("return m, nil\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+	}
+	if (genSendAndClose) {
+		printer->Print(vars, "func (x *$StreamType$) SendAndClose(m *$Response$) error {\n");
+		printer->Indent();
+		printer->Print("return x.ServerStream.SendMsg(m)\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+	}
+
+}
+
+// Generates Client method signature source
+void GenerateClientMethodSignature(const grpc_generator::Method *method, grpc_generator::Printer *printer,
+                                   std::map<grpc::string, grpc::string> vars) {
+	vars["Method"] = exportName(method->name());
+	vars["Request"] = ", in *" + ((vars["CustomMethodIO"] == "") ? method->input_name() : vars["CustomMethodIO"]);
+	if (method->ClientOnlyStreaming() || method->BidiStreaming()) {
+		vars["Request"] = "";
+	}
+	vars["Response"] = "* " + method->output_name();
+	if (method->ClientOnlyStreaming() || method->BidiStreaming() || method->ServerOnlyStreaming()) {
+		vars["Response"] = vars["Service"] + "_" + vars["Method"] + "Client" ;
+	}
+	printer->Print(vars, "$Method$(ctx $context$.Context$Request$, \n\topts... $grpc$.CallOption) ($Response$, error)");
+}
+
+// Generates Client method source
+void GenerateClientMethod(const grpc_generator::Method *method, grpc_generator::Printer *printer,
+                          std::map<grpc::string, grpc::string> vars) {
+	printer->Print(vars, "func (c *$ServiceUnexported$Client) ");
+	GenerateClientMethodSignature(method, printer, vars);
+	printer->Print(" {\n");
+	printer->Indent();
+	vars["Method"] = exportName(method->name());
+	vars["Request"] = (vars["CustomMethodIO"] == "") ? method->input_name() : vars["CustomMethodIO"];
+	vars["Response"] = method->output_name();
+	vars["FullMethodName"] = "/" + vars["Package"] + "." + vars["Service"] + "/" + vars["Method"];
+	if (method->NoStreaming()) {
+		printer->Print(vars, "out := new($Response$)\n");
+		printer->Print(vars, "err := $grpc$.Invoke(ctx, \"$FullMethodName$\", in, out, c.cc, opts...)\n");
+		printer->Print("if err != nil { return nil, err }\n");
+		printer->Print("return out, nil\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+		return;
+	}
+	vars["StreamType"] = vars["ServiceUnexported"] + vars["Method"] + "Client";
+	printer->Print(vars, "stream, err := $grpc$.NewClientStream(ctx, &$MethodDesc$, c.cc, \"$FullMethodName$\", opts...)\n");
+	printer->Print("if err != nil { return nil, err }\n");
+
+	printer->Print(vars, "x := &$StreamType${stream}\n");
+	if (method->ServerOnlyStreaming()) {
+		printer->Print("if err := x.ClientStream.SendMsg(in); err != nil { return nil, err }\n");
+		printer->Print("if err := x.ClientStream.CloseSend(); err != nil { return nil, err }\n");
+	}
+	printer->Print("return x,nil\n");
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	bool genSend = method->BidiStreaming() || method->ClientOnlyStreaming();
+	bool genRecv = method->BidiStreaming() || method->ServerOnlyStreaming();
+	bool genCloseAndRecv = method->ClientOnlyStreaming();
+
+	//Stream interface
+	printer->Print(vars, "type $Service$_$Method$Client interface {\n");
+	printer->Indent();
+	if (genSend) {
+		printer->Print(vars, "Send(*$Request$) error\n");
+	}
+	if (genRecv) {
+		printer->Print(vars, "Recv() (*$Response$, error)\n");
+	}
+	if (genCloseAndRecv) {
+		printer->Print(vars, "CloseAndRecv() (*$Response$, error)\n");
+	}
+	printer->Print(vars, "$grpc$.ClientStream\n");
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	//Stream Client
+	printer->Print(vars, "type $StreamType$ struct{\n");
+	printer->Indent();
+	printer->Print(vars, "$grpc$.ClientStream\n");
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	if (genSend) {
+		printer->Print(vars, "func (x *$StreamType$) Send(m *$Request$) error {\n");
+		printer->Indent();
+		printer->Print("return x.ClientStream.SendMsg(m)\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+	}
+
+	if (genRecv) {
+		printer->Print(vars, "func (x *$StreamType$) Recv() (*$Response$, error) {\n");
+		printer->Indent();
+		printer->Print(vars, "m := new($Response$)\n");
+		printer->Print("if err := x.ClientStream.RecvMsg(m); err != nil { return nil, err }\n");
+		printer->Print("return m, nil\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+	}
+
+	if (genCloseAndRecv) {
+		printer->Print(vars, "func (x *$StreamType$) CloseAndRecv() (*$Response$, error) {\n");
+		printer->Indent();
+		printer->Print("if err := x.ClientStream.CloseSend(); err != nil { return nil, err }\n");
+		printer->Print(vars, "m := new ($Response$)\n");
+		printer->Print("if err := x.ClientStream.RecvMsg(m); err != nil { return nil, err }\n");
+		printer->Print("return m, nil\n");
+		printer->Outdent();
+		printer->Print("}\n\n");
+	}
+}
+
+// Generates client API for the service
+void GenerateService(const grpc_generator::Service *service, grpc_generator::Printer* printer,
+                     std::map<grpc::string, grpc::string> vars) {
+	vars["Service"] = exportName(service->name());
+	// Client Interface
+	printer->Print(vars, "// Client API for $Service$ service\n");
+	printer->Print(vars, "type $Service$Client interface{\n");
+	printer->Indent();
+	for (int i = 0; i < service->method_count(); i++) {
+		GenerateClientMethodSignature(service->method(i).get(), printer, vars);
+		printer->Print("\n");
+	}
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	// Client structure
+	vars["ServiceUnexported"] = unexportName(vars["Service"]);
+	printer->Print(vars, "type $ServiceUnexported$Client struct {\n");
+	printer->Indent();
+	printer->Print(vars, "cc *$grpc$.ClientConn\n");
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	// NewClient
+	printer->Print(vars, "func New$Service$Client(cc *$grpc$.ClientConn) $Service$Client {\n");
+	printer->Indent();
+	printer->Print(vars, "return &$ServiceUnexported$Client{cc}");
+	printer->Outdent();
+	printer->Print("\n}\n\n");
+
+	int unary_methods = 0, streaming_methods = 0;
+	vars["ServiceDesc"] = "_" + vars["Service"] + "_serviceDesc";
+	for (int i = 0; i < service->method_count(); i++) {
+		auto method = service->method(i);
+		if (method->NoStreaming()) {
+			vars["MethodDesc"] = vars["ServiceDesc"] + ".Method[" + as_string(unary_methods) + "]";
+			unary_methods++;
+		} else {
+			vars["MethodDesc"] = vars["ServiceDesc"] + ".Streams[" + as_string(streaming_methods) + "]";
+			streaming_methods++;
+		}
+		GenerateClientMethod(method.get(), printer, vars);
+	}
+
+	//Server Interface
+	printer->Print(vars, "// Server API for $Service$ service\n");
+	printer->Print(vars, "type $Service$Server interface {\n");
+	printer->Indent();
+	for (int i = 0; i < service->method_count(); i++) {
+		GenerateServerMethodSignature(service->method(i).get(), printer, vars);
+		printer->Print("\n");
+	}
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	// Server registration.
+	printer->Print(vars, "func Register$Service$Server(s *$grpc$.Server, srv $Service$Server) {\n");
+	printer->Indent();
+	printer->Print(vars, "s.RegisterService(&$ServiceDesc$, srv)\n");
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+	for (int i = 0; i < service->method_count(); i++) {
+		GenerateServerMethod(service->method(i).get(), printer, vars);
+		printer->Print("\n");
+	}
+
+
+	//Service Descriptor
+	printer->Print(vars, "var $ServiceDesc$ = $grpc$.ServiceDesc{\n");
+	printer->Indent();
+	printer->Print(vars, "ServiceName: \"$Package$.$Service$\",\n");
+	printer->Print(vars, "HandlerType: (*$Service$Server)(nil),\n");
+	printer->Print(vars, "Methods: []$grpc$.MethodDesc{\n");
+	printer->Indent();
+	for (int i = 0; i < service->method_count(); i++) {
+		auto method = service->method(i);
+		vars["Method"] = method->name();
+		vars["Handler"] = "_" + vars["Service"] + "_" + vars["Method"] + "_Handler";
+		if (method->NoStreaming()) {
+			printer->Print("{\n");
+			printer->Indent();
+			printer->Print(vars, "MethodName: \"$Method$\",\n");
+			printer->Print(vars, "Handler: $Handler$, \n");
+			printer->Outdent();
+			printer->Print("},\n");
+		}
+	}
+	printer->Outdent();
+	printer->Print("},\n");
+	printer->Print(vars, "Streams: []$grpc$.StreamDesc{\n");
+	printer->Indent();
+	for (int i = 0; i < service->method_count(); i++) {
+		auto method = service->method(i);
+		vars["Method"] = method->name();
+		vars["Handler"] = "_" + vars["Service"] + "_" + vars["Method"] + "_Handler";
+		if (!method->NoStreaming()) {
+			printer->Print("{\n");
+			printer->Indent();
+			printer->Print(vars, "StreamName: \"$Method$\",\n");
+			printer->Print(vars, "Handler: $Handler$, \n");
+			if (method->ClientOnlyStreaming()) {
+				printer->Print("ClientStreams: true,\n");
+			} else if (method->ServerOnlyStreaming()) {
+				printer->Print("ServerStreams: true,\n");
+			} else {
+				printer->Print("ServerStreams: true,\n");
+				printer->Print("ClientStreams: true,\n");
+			}
+			printer->Outdent();
+			printer->Print("},\n");
+		}
+	}
+	printer->Outdent();
+	printer->Print("},\n");
+	printer->Outdent();
+	printer->Print("}\n\n");
+
+}
+
+
+// Returns source for the service
+grpc::string GenerateServiceSource(grpc_generator::File *file,
+                                   const grpc_generator::Service *service,
+                                   grpc_go_generator::Parameters *parameters) {
+	grpc::string out;
+	auto p = file->CreatePrinter(&out);
+	auto printer = p.get();
+	std::map<grpc::string, grpc::string> vars;
+	vars["Package"] = parameters->package_name;
+	vars["grpc"] = "grpc";
+	vars["context"] = "context";
+	GenerateImports(file, printer, vars);
+	if (parameters->custom_method_io_type != "") {
+		vars["CustomMethodIO"] = parameters->custom_method_io_type;
+	}
+	GenerateService(service, printer, vars);
+	return out;
+}
+}// Namespace grpc_go_generator
\ No newline at end of file

grpc/src/compiler/go_generator.h

+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_INTERNAL_COMPILER_GO_GENERATOR_H
+#define GRPC_INTERNAL_COMPILER_GO_GENERATOR_H
+
+//go generator is used to generate GRPC code for serialization system, such as flatbuffers
+#include <memory>
+#include <vector>
+
+#include "src/compiler/schema_interface.h"
+
+namespace grpc_go_generator {
+
+struct Parameters {
+	//Defines the custom parameter types for methods
+	//eg: flatbuffers uses flatbuffers.Builder as input for the client and output for the server
+	grpc::string custom_method_io_type;
+
+	//Package name for the service
+	grpc::string package_name;
+};
+
+// Return the source of the generated service file.
+grpc::string GenerateServiceSource(grpc_generator::File *file,
+                                   const grpc_generator::Service *service,
+                                   grpc_go_generator::Parameters *parameters);
+
+}
+
+#endif  // GRPC_INTERNAL_COMPILER_GO_GENERATOR_H

grpc/src/compiler/schema_interface.h

@@ -59,6 +59,8 @@ namespace grpc_generator {
 
     virtual grpc::string input_type_name() const = 0;
     virtual grpc::string output_type_name() const = 0;
+    virtual grpc::string input_name() const = 0;
+    virtual grpc::string output_name() const = 0;
 
     virtual bool NoStreaming() const = 0;
     virtual bool ClientOnlyStreaming() const = 0;
@@ -98,6 +100,7 @@ namespace grpc_generator {
     virtual grpc::string package() const = 0;
     virtual std::vector<grpc::string> package_parts() const = 0;
     virtual grpc::string additional_headers() const = 0;
+    virtual grpc::string additional_imports() const = 0;
 
     virtual int service_count() const = 0;
     virtual std::unique_ptr<const Service> service(int i) const = 0;

grpc/tests/go_test.go

+package testing
+
+import (
+	"../../tests/MyGame/Example"
+
+	"net"
+	"testing"
+
+	"github.com/google/flatbuffers/go"
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+)
+
+type server struct{}
+
+// test used to send and receive in grpc methods
+var test string = "Flatbuffers"
+var addr string = "0.0.0.0:50051"
+
+// gRPC server store method
+func (s *server) Store(context context.Context, in *Example.Monster) (*flatbuffers.Builder, error) {
+	b := flatbuffers.NewBuilder(0)
+	i := b.CreateString(test)
+	Example.StatStart(b)
+	Example.StatAddId(b, i)
+	b.Finish(Example.StatEnd(b))
+	return b, nil
+
+}
+
+// gRPC server retrieve method
+func (s *server) Retrieve(context context.Context, in *Example.Stat) (*flatbuffers.Builder, error) {
+	b := flatbuffers.NewBuilder(0)
+	i := b.CreateString(test)
+	Example.MonsterStart(b)
+	Example.MonsterAddName(b, i)
+	b.Finish(Example.MonsterEnd(b))
+	return b, nil
+}
+
+func StoreClient(c Example.MonsterStorageClient, t *testing.T) {
+	b := flatbuffers.NewBuilder(0)
+	i := b.CreateString(test)
+	Example.MonsterStart(b)
+	Example.MonsterAddName(b, i)
+	b.Finish(Example.MonsterEnd(b))
+	out, err := c.Store(context.Background(), b)
+	if err != nil {
+		t.Fatal("Store client failed: %v", err)
+	}
+	if string(out.Id()) != test {
+		t.Errorf("StoreClient failed: expected=%s, got=%s\n", test, out.Id())
+		t.Fail()
+	}
+}
+
+func RetrieveClient(c Example.MonsterStorageClient, t *testing.T) {
+	b := flatbuffers.NewBuilder(0)
+	i := b.CreateString(test)
+	Example.StatStart(b)
+	Example.StatAddId(b, i)
+	b.Finish(Example.StatEnd(b))
+	out, err := c.Retrieve(context.Background(), b)
+	if err != nil {
+		t.Fatal("Retrieve client failed: %v", err)
+	}
+	if string(out.Name()) != test {
+		t.Errorf("RetrieveClient failed: expected=%s, got=%s\n", test, out.Name())
+		t.Fail()
+	}
+}
+
+func TestGRPC(t *testing.T) {
+	lis, err := net.Listen("tcp", addr)
+	if err != nil {
+		t.Fatalf("Failed to listen: %v", err)
+	}
+	ser := grpc.NewServer(grpc.CustomCodec(flatbuffers.FlatbuffersCodec{}))
+	Example.RegisterMonsterStorageServer(ser, &server{})
+	go func() {
+		if err := ser.Serve(lis); err != nil {
+			t.Fatalf("Failed to serve: %v", err)
+			t.FailNow()
+		}
+	}()
+	conn, err := grpc.Dial(addr, grpc.WithInsecure(), grpc.WithCodec(flatbuffers.FlatbuffersCodec{}))
+	if err != nil {
+		t.Fatal("Failed to connect: %v", err)
+	}
+	defer conn.Close()
+	client := Example.NewMonsterStorageClient(conn)
+	StoreClient(client, t)
+	RetrieveClient(client, t)
+}

include/flatbuffers/idl.h

@@ -708,9 +708,15 @@ extern std::string BinaryMakeRule(const Parser &parser,
                                   const std::string &path,
                                   const std::string &file_name);
 
-// Generate GRPC interfaces.
+// Generate GRPC Cpp interfaces.
 // See idl_gen_grpc.cpp.
-bool GenerateGRPC(const Parser &parser,
+bool GenerateCppGRPC(const Parser &parser,
+                     const std::string &path,
+                     const std::string &file_name);
+
+// Generate GRPC Go interfaces.
+// See idl_gen_grpc.cpp.
+bool GenerateGoGRPC(const Parser &parser,
                     const std::string &path,
                     const std::string &file_name);
 

src/flatc.cpp

@@ -33,6 +33,9 @@ struct Generator {
   const char *generator_opt_short;
   const char *generator_opt_long;
   const char *lang_name;
+  bool (*generateGRPC)(const flatbuffers::Parser &parser,
+                       const std::string &path,
+                       const std::string &file_name);
   flatbuffers::IDLOptions::Language lang;
   const char *generator_help;
 
@@ -43,45 +46,50 @@ struct Generator {
 
 const Generator generators[] = {
   { flatbuffers::GenerateBinary,   "-b", "--binary", "binary",
+    nullptr,
     flatbuffers::IDLOptions::kMAX,
     "Generate wire format binaries for any data definitions",
     flatbuffers::BinaryMakeRule },
   { flatbuffers::GenerateTextFile, "-t", "--json", "text",
+    nullptr,
     flatbuffers::IDLOptions::kMAX,
     "Generate text output for any data definitions",
     flatbuffers::TextMakeRule },
   { flatbuffers::GenerateCPP,      "-c", "--cpp", "C++",
+    flatbuffers::GenerateCppGRPC,
     flatbuffers::IDLOptions::kMAX,
     "Generate C++ headers for tables/structs",
     flatbuffers::CPPMakeRule },
   { flatbuffers::GenerateGo,       "-g", "--go", "Go",
+    flatbuffers::GenerateGoGRPC,
     flatbuffers::IDLOptions::kGo,
     "Generate Go files for tables/structs",
     flatbuffers::GeneralMakeRule },
   { flatbuffers::GenerateGeneral,  "-j", "--java", "Java",
+    nullptr,
     flatbuffers::IDLOptions::kJava,
     "Generate Java classes for tables/structs",
     flatbuffers::GeneralMakeRule },
   { flatbuffers::GenerateJS,       "-s", "--js", "JavaScript",
+    nullptr,
     flatbuffers::IDLOptions::kMAX,
     "Generate JavaScript code for tables/structs",
     flatbuffers::JSMakeRule },
   { flatbuffers::GenerateGeneral,  "-n", "--csharp", "C#",
+    nullptr,
     flatbuffers::IDLOptions::kCSharp,
     "Generate C# classes for tables/structs",
     flatbuffers::GeneralMakeRule },
   { flatbuffers::GeneratePython,   "-p", "--python", "Python",
+    nullptr,
     flatbuffers::IDLOptions::kMAX,
     "Generate Python files for tables/structs",
     flatbuffers::GeneralMakeRule },
   { flatbuffers::GeneratePhp, nullptr, "--php", "PHP",
+    nullptr,
     flatbuffers::IDLOptions::kMAX,
     "Generate PHP files for tables/structs",
     flatbuffers::GeneralMakeRule },
-  { flatbuffers::GenerateGRPC, nullptr, "--grpc", "GRPC",
-    flatbuffers::IDLOptions::kMAX,
-    "Generate GRPC interfaces",
-    flatbuffers::CPPMakeRule },
 };
 
 const char *g_program_name = nullptr;
@@ -170,6 +178,7 @@ int main(int argc, const char *argv[]) {
   bool print_make_rules = false;
   bool raw_binary = false;
   bool schema_binary = false;
+  bool grpc_enabled = false;
   std::vector<std::string> filenames;
   std::vector<const char *> include_directories;
   std::vector<const char *> conform_include_directories;
@@ -243,6 +252,8 @@ int main(int argc, const char *argv[]) {
       } else if(arg == "--version") {
         printf("flatc version %s\n", FLATC_VERSION);
         exit(0);
+      } else if(arg == "--grpc") {
+        grpc_enabled = true;
       } else {
         for (size_t i = 0; i < num_generators; ++i) {
           if (arg == generators[i].generator_opt_long ||
@@ -360,6 +371,17 @@ int main(int argc, const char *argv[]) {
               printf("%s\n", flatbuffers::WordWrap(
                   make_rule, 80, " ", " \\").c_str());
           }
+          if (grpc_enabled) {
+            if (generators[i].generateGRPC != nullptr) {
+              if (!generators[i].generateGRPC(*g_parser, output_path, filebase)) {
+                    Error(std::string("Unable to generate GRPC interface for") +
+                          generators[i].lang_name);
+              }
+            } else {
+                Error(std::string("GRPC interface generator not implemented for ") +
+                      generators[i].lang_name);
+            }
+          }
         }
       }
 

src/idl_gen_grpc.cpp

@@ -19,8 +19,10 @@
 #include "flatbuffers/flatbuffers.h"
 #include "flatbuffers/idl.h"
 #include "flatbuffers/util.h"
+#include "flatbuffers/code_generators.h"
 
 #include "src/compiler/cpp_generator.h"
+#include "src/compiler/go_generator.h"
 
 namespace flatbuffers {
 
@@ -52,6 +54,14 @@ class FlatBufMethod : public grpc_generator::Method {
     return GRPCType(*method_->response);
   }
 
+  std::string input_name() const {
+    return (*method_->request).name;
+  }
+
+  std::string output_name() const {
+    return (*method_->response).name;
+  }
+
   bool NoStreaming() const { return streaming_ == kNone; }
   bool ClientOnlyStreaming() const { return streaming_ == kClient; }
   bool ServerOnlyStreaming() const { return streaming_ == kServer; }
@@ -159,6 +169,10 @@ class FlatBufFile : public grpc_generator::File {
     return "#include \"flatbuffers/grpc.h\"\n";
   }
 
+  std::string additional_imports() const {
+    return "import \"github.com/google/flatbuffers/go\"";
+  }
+
   int service_count() const {
     return static_cast<int>(parser_.services_.vec.size());
   };
@@ -178,7 +192,47 @@ class FlatBufFile : public grpc_generator::File {
   const std::string &file_name_;
 };
 
-bool GenerateGRPC(const Parser &parser,
+class GoGRPCGenerator : public flatbuffers::BaseGenerator {
+ public:
+  GoGRPCGenerator(const Parser &parser, const std::string &path,
+                  const std::string &file_name)
+    : BaseGenerator(parser, path, file_name, "", "" /*Unused*/),
+      parser_(parser), path_(path), file_name_(file_name) {}
+
+  bool generate() {
+    FlatBufFile file(parser_, file_name_);
+    grpc_go_generator::Parameters p;
+    p.custom_method_io_type = "flatbuffers.Builder";
+    for (int i = 0; i < file.service_count(); i++) {
+      auto service = file.service(i);
+      const Definition *def = parser_.services_.vec[i];
+      p.package_name = LastNamespacePart(*(def->defined_namespace));
+      std::string output = grpc_go_generator::GenerateServiceSource(&file, service.get(), &p);
+      std::string filename = NamespaceDir(*def->defined_namespace) + def->name + "_grpc.go";
+      if (!flatbuffers::SaveFile(filename.c_str(), output, false))
+        return false;
+    }
+    return true;
+  }
+
+ protected:
+  const Parser &parser_;
+  const std::string &path_, &file_name_;
+};
+
+bool GenerateGoGRPC(const Parser &parser,
+                    const std::string &path,
+                    const std::string &file_name) {
+  int nservices = 0;
+  for (auto it = parser.services_.vec.begin();
+       it != parser.services_.vec.end(); ++it) {
+    if (!(*it)->generated) nservices++;
+  }
+  if (!nservices) return true;
+  return GoGRPCGenerator(parser, path, file_name).generate();
+}
+
+bool GenerateCppGRPC(const Parser &parser,
                   const std::string &/*path*/,
                   const std::string &file_name) {
 

tests/MyGame/Example/MonsterStorage_grpc.go

+//Generated by gRPC Go plugin
+//If you make any local changes, they will be lost
+//source: monster_test
+
+package Example
+
+import "github.com/google/flatbuffers/go"
+
+import (
+  context "golang.org/x/net/context"
+  grpc "google.golang.org/grpc"
+)
+
+// Client API for MonsterStorage service
+type MonsterStorageClient interface{
+  Store(ctx context.Context, in *flatbuffers.Builder, 
+  	opts... grpc.CallOption) (* Stat, error)  
+  Retrieve(ctx context.Context, in *flatbuffers.Builder, 
+  	opts... grpc.CallOption) (* Monster, error)  
+}
+
+type monsterStorageClient struct {
+  cc *grpc.ClientConn
+}
+
+func NewMonsterStorageClient(cc *grpc.ClientConn) MonsterStorageClient {
+  return &monsterStorageClient{cc}
+}
+
+func (c *monsterStorageClient) Store(ctx context.Context, in *flatbuffers.Builder, 
+	opts... grpc.CallOption) (* Stat, error) {
+  out := new(Stat)
+  err := grpc.Invoke(ctx, "/Example.MonsterStorage/Store", in, out, c.cc, opts...)
+  if err != nil { return nil, err }
+  return out, nil
+}
+
+func (c *monsterStorageClient) Retrieve(ctx context.Context, in *flatbuffers.Builder, 
+	opts... grpc.CallOption) (* Monster, error) {
+  out := new(Monster)
+  err := grpc.Invoke(ctx, "/Example.MonsterStorage/Retrieve", in, out, c.cc, opts...)
+  if err != nil { return nil, err }
+  return out, nil
+}
+
+// Server API for MonsterStorage service
+type MonsterStorageServer interface {
+  Store(context.Context, *Monster) (*flatbuffers.Builder, error)  
+  Retrieve(context.Context, *Stat) (*flatbuffers.Builder, error)  
+}
+
+func RegisterMonsterStorageServer(s *grpc.Server, srv MonsterStorageServer) {
+  s.RegisterService(&_MonsterStorage_serviceDesc, srv)
+}
+
+func _MonsterStorage_Store_Handler(srv interface{}, ctx context.Context,
+	dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+  in := new(Monster)
+  if err := dec(in); err != nil { return nil, err }
+  if interceptor == nil { return srv.(MonsterStorageServer).Store(ctx, in) }
+  info := &grpc.UnaryServerInfo{
+    Server: srv,
+    FullMethod: "/Example.MonsterStorage/Store",
+  }
+  
+  handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+    return srv.(MonsterStorageServer).Store(ctx, req.(* Monster))
+  }
+  return interceptor(ctx, in, info, handler)
+}
+
+
+func _MonsterStorage_Retrieve_Handler(srv interface{}, ctx context.Context,
+	dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+  in := new(Stat)
+  if err := dec(in); err != nil { return nil, err }
+  if interceptor == nil { return srv.(MonsterStorageServer).Retrieve(ctx, in) }
+  info := &grpc.UnaryServerInfo{
+    Server: srv,
+    FullMethod: "/Example.MonsterStorage/Retrieve",
+  }
+  
+  handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+    return srv.(MonsterStorageServer).Retrieve(ctx, req.(* Stat))
+  }
+  return interceptor(ctx, in, info, handler)
+}
+
+
+var _MonsterStorage_serviceDesc = grpc.ServiceDesc{
+  ServiceName: "Example.MonsterStorage",
+  HandlerType: (*MonsterStorageServer)(nil),
+  Methods: []grpc.MethodDesc{
+    {
+      MethodName: "Store",
+      Handler: _MonsterStorage_Store_Handler, 
+    },
+    {
+      MethodName: "Retrieve",
+      Handler: _MonsterStorage_Retrieve_Handler, 
+    },
+  },
+  Streams: []grpc.StreamDesc{
+  },
+}
+