Find full configuration path inside a submodule

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1

I am trying to create a date submodule. Here is a snippet of of it.

options = {
  day = lib.mkOption {
    description = "The day.";
    type = types.nullOr (types.numbers.between 1 31);
    default = null;
  };
  month = lib.mkOption {
    description = "The month.";
    type = types.nullOr (types.numbers.between 1 12);
    default = null;
  };
  year = lib.mkOption {
    description = "The year.";
    type = types.nullOr types.numbers.positive;
    default = null;
  };
...

And I am using it as a submodule as shown below.

options = {
  nixcv = lib.mkOption {
  description = "Your CV.";
    type = types.submodule {
      options = {
        startDate = lib.mkOption {
          description = "The start date.";
          type = types.submoduleWith {
            modules = [./date.nix];
          };
        };
        endDate = lib.mkOption {
          description = "The start date.";
          type = types.submoduleWith {
            modules = [./date.nix];
          };
        };
      };
    };
  };
};

And a basic config shown below.

{
  nixcv = {
    startDate = {
      year = 2021;
      month = 11;
      day = 4;
    };
    endDate = {
      year = 2023;
      month = 12;
      day = 14;
    };
  };
}

Under a certain condition, if a month is not set, I want to throw a meaningful error to the user. Within the date.nix module, I could easily throw "month was not set" but that gives no context for where the problem is in the config. It would be really nice if i could say nixcv.startDate.month is not set etc....

So far I found that I can access the parent of the date module’s name using config._module.arg.name. Alternatively, if I pass options to the submodule, and inspect options._module.args.loc it returns [ "nixcv" "endDate" "_module" "args" ] which I could filter and concat to get what I want.

Is this the best way to access all the parent config names of a submodule or is there a better way?