protogen: Distinguish between empty and nil messages

Refs #59

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

rpc/message/test/message.go

@@ -126,7 +126,6 @@ func testCompatibility(t *testing.T, msgGen func(empty bool) message.Message) {
 		}
 	}
 	t.Run("empty", func(t *testing.T) {
-		t.Skip()
 		msg := msgGen(true)
 		t.Run(fmt.Sprintf("Binary_%T", msg), func(t *testing.T) {
 			compareBinary(t, msg)

util/protogen/internalgengo/proto.go

@@ -174,7 +174,7 @@ func emitMarshalRaw(g *protogen.GeneratedFile, f *protogen.Field, name string) {
 			name += "[i]"
 		}
 
-		g.P("if ", notNil(name), " && ", name, ".StableSize() != 0 {")
+		g.P("if ", notNil(name), " {")
 		g.P(name, ".EmitProtobuf(mm.AppendMessage(", f.Desc.Number(), "))")
 		g.P("}")
 		return