Add an optional implementation of streams using generics (#7057)

cmd/protoc-gen-go-grpc/grpc.go

@@ -174,8 +174,13 @@ func generateFileContent(gen *protogen.Plugin, file *protogen.File, g *protogen.
 
  g.P("// This is a compile-time assertion to ensure that this generated file")
  g.P("// is compatible with the grpc package it is being compiled against.")
- g.P("// Requires gRPC-Go v1.62.0 or later.")
- g.P("const _ = ", grpcPackage.Ident("SupportPackageIsVersion8")) // When changing, update version number above.
+ if *useGenericStreams {
+ g.P("// Requires gRPC-Go v1.64.0 or later.")
+ g.P("const _ = ", grpcPackage.Ident("SupportPackageIsVersion9"))
+ } else {
+ g.P("// Requires gRPC-Go v1.62.0 or later.")
+ g.P("const _ = ", grpcPackage.Ident("SupportPackageIsVersion8")) // When changing, update version number above.
+ }
  g.P()
  for _, service := range file.Services {
  genService(gen, file, g, service)
@@ -299,12 +304,27 @@ func clientSignature(g *protogen.GeneratedFile, method *protogen.Method) string
  if !method.Desc.IsStreamingClient() && !method.Desc.IsStreamingServer() {
  s += "*" + g.QualifiedGoIdent(method.Output.GoIdent)
  } else {
- s += method.Parent.GoName + "_" + method.GoName + "Client"
+ if *useGenericStreams {
+ s += clientStreamInterface(g, method)
+ } else {
+ s += method.Parent.GoName + "_" + method.GoName + "Client"
+ }
  }
  s += ", error)"
  return s
 }
 
+func clientStreamInterface(g *protogen.GeneratedFile, method *protogen.Method) string {
+ typeParam := g.QualifiedGoIdent(method.Input.GoIdent) + ", " + g.QualifiedGoIdent(method.Output.GoIdent)
+ if method.Desc.IsStreamingClient() && method.Desc.IsStreamingServer() {
+ return g.QualifiedGoIdent(grpcPackage.Ident("BidiStreamingClient")) + "[" + typeParam + "]"
+ } else if method.Desc.IsStreamingClient() {
+ return g.QualifiedGoIdent(grpcPackage.Ident("ClientStreamingClient")) + "[" + typeParam + "]"
+ } else { // i.e. if method.Desc.IsStreamingServer()
+ return g.QualifiedGoIdent(grpcPackage.Ident("ServerStreamingClient")) + "[" + g.QualifiedGoIdent(method.Output.GoIdent) + "]"
+ }
+}
+
 func genClientMethod(gen *protogen.Plugin, file *protogen.File, g *protogen.GeneratedFile, method *protogen.Method, index int) {
  service := method.Parent
  fmSymbol := helper.formatFullMethodSymbol(service, method)
@@ -323,11 +343,17 @@ func genClientMethod(gen *protogen.Plugin, file *protogen.File, g *protogen.Gene
  g.P()
  return
  }
- streamType := unexport(service.GoName) + method.GoName + "Client"
+
+ streamImpl := unexport(service.GoName) + method.GoName + "Client"
+ if *useGenericStreams {
+ typeParam := g.QualifiedGoIdent(method.Input.GoIdent) + ", " + g.QualifiedGoIdent(method.Output.GoIdent)
+ streamImpl = g.QualifiedGoIdent(grpcPackage.Ident("GenericClientStream")) + "[" + typeParam + "]"
+ }
+
  serviceDescVar := service.GoName + "_ServiceDesc"
  g.P("stream, err := c.cc.NewStream(ctx, &", serviceDescVar, ".Streams[", index, `], `, fmSymbol, `, cOpts...)`)
  g.P("if err != nil { return nil, err }")
- g.P("x := &", streamType, "{stream}")
+ g.P("x := &", streamImpl, "{ClientStream: stream}")
  if !method.Desc.IsStreamingClient() {
  g.P("if err := x.ClientStream.SendMsg(in); err != nil { return nil, err }")
  g.P("if err := x.ClientStream.CloseSend(); err != nil { return nil, err }")
@@ -336,11 +362,20 @@ func genClientMethod(gen *protogen.Plugin, file *protogen.File, g *protogen.Gene
  g.P("}")
  g.P()
 
+ // Auxiliary types aliases, for backwards compatibility.
+ if *useGenericStreams {
+ g.P("// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.")
+ g.P("type ", service.GoName, "_", method.GoName, "Client = ", clientStreamInterface(g, method))
+ g.P()
+ return
+ }
+
+ // Stream auxiliary types and methods, if we're not taking advantage of the
+ // pre-implemented generic types and their methods.
  genSend := method.Desc.IsStreamingClient()
  genRecv := method.Desc.IsStreamingServer()
  genCloseAndRecv := !method.Desc.IsStreamingServer()
 
- // Stream auxiliary types and methods.
  g.P("type ", service.GoName, "_", method.GoName, "Client interface {")
  if genSend {
  g.P("Send(*", method.Input.GoIdent, ") error")
@@ -355,27 +390,27 @@ func genClientMethod(gen *protogen.Plugin, file *protogen.File, g *protogen.Gene
  g.P("}")
  g.P()
 
- g.P("type ", streamType, " struct {")
+ g.P("type ", streamImpl, " struct {")
  g.P(grpcPackage.Ident("ClientStream"))
  g.P("}")
  g.P()
 
  if genSend {
- g.P("func (x *", streamType, ") Send(m *", method.Input.GoIdent, ") error {")
+ g.P("func (x *", streamImpl, ") Send(m *", method.Input.GoIdent, ") error {")
  g.P("return x.ClientStream.SendMsg(m)")
  g.P("}")
  g.P()
  }
  if genRecv {
- g.P("func (x *", streamType, ") Recv() (*", method.Output.GoIdent, ", error) {")
+ g.P("func (x *", streamImpl, ") Recv() (*", method.Output.GoIdent, ", error) {")
  g.P("m := new(", method.Output.GoIdent, ")")
  g.P("if err := x.ClientStream.RecvMsg(m); err != nil { return nil, err }")
  g.P("return m, nil")
  g.P("}")
  g.P()
  }
  if genCloseAndRecv {
- g.P("func (x *", streamType, ") CloseAndRecv() (*", method.Output.GoIdent, ", error) {")
+ g.P("func (x *", streamImpl, ") CloseAndRecv() (*", method.Output.GoIdent, ", error) {")
  g.P("if err := x.ClientStream.CloseSend(); err != nil { return nil, err }")
  g.P("m := new(", method.Output.GoIdent, ")")
  g.P("if err := x.ClientStream.RecvMsg(m); err != nil { return nil, err }")
@@ -396,7 +431,11 @@ func serverSignature(g *protogen.GeneratedFile, method *protogen.Method) string
  reqArgs = append(reqArgs, "*"+g.QualifiedGoIdent(method.Input.GoIdent))
  }
  if method.Desc.IsStreamingClient() || method.Desc.IsStreamingServer() {
- reqArgs = append(reqArgs, method.Parent.GoName+"_"+method.GoName+"Server")
+ if *useGenericStreams {
+ reqArgs = append(reqArgs, serverStreamInterface(g, method))
+ } else {
+ reqArgs = append(reqArgs, method.Parent.GoName+"_"+method.GoName+"Server")
+ }
  }
  return method.GoName + "(" + strings.Join(reqArgs, ", ") + ") " + ret
 }
@@ -442,6 +481,17 @@ func genServiceDesc(file *protogen.File, g *protogen.GeneratedFile, serviceDescV
  g.P()
 }
 
+func serverStreamInterface(g *protogen.GeneratedFile, method *protogen.Method) string {
+ typeParam := g.QualifiedGoIdent(method.Input.GoIdent) + ", " + g.QualifiedGoIdent(method.Output.GoIdent)
+ if method.Desc.IsStreamingClient() && method.Desc.IsStreamingServer() {
+ return g.QualifiedGoIdent(grpcPackage.Ident("BidiStreamingServer")) + "[" + typeParam + "]"
+ } else if method.Desc.IsStreamingClient() {
+ return g.QualifiedGoIdent(grpcPackage.Ident("ClientStreamingServer")) + "[" + typeParam + "]"
+ } else { // i.e. if method.Desc.IsStreamingServer()
+ return g.QualifiedGoIdent(grpcPackage.Ident("ServerStreamingServer")) + "[" + g.QualifiedGoIdent(method.Output.GoIdent) + "]"
+ }
+}
+
 func genServerMethod(gen *protogen.Plugin, file *protogen.File, g *protogen.GeneratedFile, method *protogen.Method, hnameFuncNameFormatter func(string) string) string {
  service := method.Parent
  hname := fmt.Sprintf("_%s_%s_Handler", service.GoName, method.GoName)
@@ -464,23 +514,38 @@ func genServerMethod(gen *protogen.Plugin, file *protogen.File, g *protogen.Gene
  g.P()
  return hname
  }
- streamType := unexport(service.GoName) + method.GoName + "Server"
+
+ streamImpl := unexport(service.GoName) + method.GoName + "Server"
+ if *useGenericStreams {
+ typeParam := g.QualifiedGoIdent(method.Input.GoIdent) + ", " + g.QualifiedGoIdent(method.Output.GoIdent)
+ streamImpl = g.QualifiedGoIdent(grpcPackage.Ident("GenericServerStream")) + "[" + typeParam + "]"
+ }
+
  g.P("func ", hnameFuncNameFormatter(hname), "(srv interface{}, stream ", grpcPackage.Ident("ServerStream"), ") error {")
  if !method.Desc.IsStreamingClient() {
  g.P("m := new(", method.Input.GoIdent, ")")
  g.P("if err := stream.RecvMsg(m); err != nil { return err }")
- g.P("return srv.(", service.GoName, "Server).", method.GoName, "(m, &", streamType, "{stream})")
+ g.P("return srv.(", service.GoName, "Server).", method.GoName, "(m, &", streamImpl, "{ServerStream: stream})")
  } else {
- g.P("return srv.(", service.GoName, "Server).", method.GoName, "(&", streamType, "{stream})")
+ g.P("return srv.(", service.GoName, "Server).", method.GoName, "(&", streamImpl, "{ServerStream: stream})")
  }
  g.P("}")
  g.P()
 
+ // Auxiliary types aliases, for backwards compatibility.
+ if *useGenericStreams {
+ g.P("// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.")
+ g.P("type ", service.GoName, "_", method.GoName, "Server = ", serverStreamInterface(g, method))
+ g.P()
+ return hname
+ }
+
+ // Stream auxiliary types and methods, if we're not taking advantage of the
+ // pre-implemented generic types and their methods.
  genSend := method.Desc.IsStreamingServer()
  genSendAndClose := !method.Desc.IsStreamingServer()
  genRecv := method.Desc.IsStreamingClient()
 
- // Stream auxiliary types and methods.
  g.P("type ", service.GoName, "_", method.GoName, "Server interface {")
  if genSend {
  g.P("Send(*", method.Output.GoIdent, ") error")
@@ -495,25 +560,25 @@ func genServerMethod(gen *protogen.Plugin, file *protogen.File, g *protogen.Gene
  g.P("}")
  g.P()
 
- g.P("type ", streamType, " struct {")
+ g.P("type ", streamImpl, " struct {")
  g.P(grpcPackage.Ident("ServerStream"))
  g.P("}")
  g.P()
 
  if genSend {
- g.P("func (x *", streamType, ") Send(m *", method.Output.GoIdent, ") error {")
+ g.P("func (x *", streamImpl, ") Send(m *", method.Output.GoIdent, ") error {")
  g.P("return x.ServerStream.SendMsg(m)")
  g.P("}")
  g.P()
  }
  if genSendAndClose {
- g.P("func (x *", streamType, ") SendAndClose(m *", method.Output.GoIdent, ") error {")
+ g.P("func (x *", streamImpl, ") SendAndClose(m *", method.Output.GoIdent, ") error {")
  g.P("return x.ServerStream.SendMsg(m)")
  g.P("}")
  g.P()
  }
  if genRecv {
- g.P("func (x *", streamType, ") Recv() (*", method.Input.GoIdent, ", error) {")
+ g.P("func (x *", streamImpl, ") Recv() (*", method.Input.GoIdent, ", error) {")
  g.P("m := new(", method.Input.GoIdent, ")")
  g.P("if err := x.ServerStream.RecvMsg(m); err != nil { return nil, err }")
  g.P("return m, nil")

cmd/protoc-gen-go-grpc/main.go

@@ -44,6 +44,7 @@ import (
 const version = "1.3.0"
 
 var requireUnimplemented *bool
+var useGenericStreams *bool
 
 func main() {
  showVersion := flag.Bool("version", false, "print the version and exit")
@@ -55,6 +56,7 @@ func main() {
 
  var flags flag.FlagSet
  requireUnimplemented = flags.Bool("require_unimplemented_servers", true, "set to false to match legacy behavior")
+ useGenericStreams = flags.Bool("use_generic_streams_experimental", false, "set to true to use generic types for streaming client and server objects; this flag is EXPERIMENTAL and may be changed or removed in a future release")
 
  protogen.Options{
  ParamFunc: flags.Set,

cmd/protoc-gen-go-grpc/protoc-gen-go-grpc_test.sh

@@ -30,7 +30,7 @@ popd
 
 protoc \
  --go-grpc_out="${TEMPDIR}" \
- --go-grpc_opt=paths=source_relative \
+ --go-grpc_opt=paths=source_relative,use_generic_streams_experimental=true \
  "examples/route_guide/routeguide/route_guide.proto"
 
 GOLDENFILE="examples/route_guide/routeguide/route_guide_grpc.pb.go"