default value of 0 for field is not part of enum

[zplzpl]

$ ./flatc.exe --version
flatc version 1.10.0 (Oct  3 2018 12:56:55)

Some sensitive data has been modified.

$ ./flatc.exe ./path/file.fbs --go
error: path\file.fbs(x, y): error: default value of 0 for field fields_merchant_update is not part of enum MerchantCanChanged

enum MerchantCanChanged : byte { x= 1, y, z, v, s}
table ProRequest{
	fields_merchant_update:[MerchantCanChanged];
}

On the flatc.exe 1.5.0 version, it works fine.
How should I fix it?

[vglavnyy]

I have reproduced this error on the HEAD of the master.
@aardappel
Probably this error was introduced by (f431a96).
Before f431a96:

  if (type.enum_def && IsScalar(type.base_type) && !struct_def.fixed &&
      !type.enum_def->attributes.Lookup("bit_flags") &&
      !type.enum_def->ReverseLookup(
          static_cast<int>(StringToInt(field->value.constant.c_str()))))
    Warning("enum " + type.enum_def->name +
            " does not have a declaration for this field\'s default of " +
            field->value.constant);

Since f431a96 (idl_parser.cpp 656-663):

  if (type.enum_def &&
      !type.enum_def->is_union &&
      !type.enum_def->attributes.Lookup("bit_flags") &&
      !type.enum_def->ReverseLookup(static_cast<int>(
                                 StringToInt(field->value.constant.c_str())))) {
    return Error("default value of " + field->value.constant + " for field " +
                 name + " is not part of enum " + type.enum_def->name);
  }

Checking && IsScalar(type.base_type) && !struct_def.fixed check was removed by this commit.

[aardappel]

Hah, didn't spot that, those definitely should be in there. Either of you care to fix it?

[vglavnyy]

@zplzpl Can you fix it and add a test for this case?

[precisionconage]

I can still reproduce this with latest master, e.g. by compiling the following:

enum TestEnum:ubyte {
    Test1 = 1
}

table Test {
    t:TestEnum;
}

root_type Test;

Edit: Never mind, this isn't quite the same issue. It looks like a default must always be provided for fields with an enum type where the enum doesn't contain 0. An attribute to specify a default for that case might be useful, but I'm not sure how much work that would be to implement.

[vglavnyy]

@precisionconage you are right.
Implicit "NONE" field added only for empty enum declarations, like enum TestEnum {}.
I will add tests and fix this issue.