function compileList(schema, name, result) {
  var exclude = [];

  schema.include.forEach(function (includedSchema) {
    result = compileList(includedSchema, name, result);
  });

  schema[name].forEach(function (currentType) {
    result.forEach(function (previousType, previousIndex) {
      if (previousType.tag === currentType.tag && previousType.kind === currentType.kind) {
        exclude.push(previousIndex);
      }
    });

    result.push(currentType);
  });

  return result.filter(function (type, index) {
    return exclude.indexOf(index) === -1;
  });
}
Display an error message if a mandatory option does not have a value.
Lazy calling after checking for help flags from leaf subcommand.

@api private