Added backwards compatible --no-union-value-namespacing

Change-Id: Ia78dd3b0f213e9ffa49dcec699dcbb21fe6517da
Tested: on Linux.

include/flatbuffers/idl.h

@@ -347,6 +347,7 @@ struct IDLOptions {
   bool generate_name_strings;
   bool escape_proto_identifiers;
   bool generate_object_based_api;
+  bool union_value_namespacing;
 
   // Possible options for the more general generator below.
   enum Language { kJava, kCSharp, kGo, kMAX };
@@ -368,6 +369,7 @@ struct IDLOptions {
       generate_name_strings(false),
       escape_proto_identifiers(false),
       generate_object_based_api(false),
+      union_value_namespacing(true),
       lang(IDLOptions::kJava) {}
 };
 

src/flatc.cpp

@@ -195,6 +195,8 @@ int main(int argc, const char *argv[]) {
       } else if(arg == "--scoped-enums") {
         opts.prefixed_enums = false;
         opts.scoped_enums = true;
+      } else if (arg == "--no-union-value-namespacing") {
+        opts.union_value_namespacing = false;
       } else if(arg == "--gen-mutable") {
         opts.mutable_buffer = true;
       } else if(arg == "--gen-name-strings") {

src/idl_parser.cpp

@@ -1216,10 +1216,12 @@ CheckedError Parser::ParseEnum(bool is_union, EnumDef **dest) {
       EXPECT(kTokenIdentifier);
       if (is_union) {
         ECHECK(ParseNamespacing(&full_name, &value_name));
-        // Since we can't namespace the actual enum identifiers, turn
-        // namespace parts into part of the identifier.
-        value_name = full_name;
-        std::replace(value_name.begin(), value_name.end(), '.', '_');
+        if (opts.union_value_namespacing) {
+          // Since we can't namespace the actual enum identifiers, turn
+          // namespace parts into part of the identifier.
+          value_name = full_name;
+          std::replace(value_name.begin(), value_name.end(), '.', '_');
+        }
       }
       auto prevsize = enum_def.vals.vec.size();
       auto value = enum_def.vals.vec.size()