class T::Props::Decorator

def prop_defined(name, cls, rules={})
  cls = T::Utils.resolve_alias(cls)
  if T::Utils::Nilable.is_union_with_nilclass(cls)
    # :_tnilable is introduced internally for performance purpose so that clients do not need to call
    # T::Utils::Nilable.is_tnilable(cls) again.
    # It is strictly internal: clients should always use T::Props::Utils.required_prop?() or
    # T::Props::Utils.optional_prop?() for checking whether a field is required or optional.
    rules[:_tnilable] = true
  end
  name = name.to_sym
  type = cls
  if !cls.is_a?(Module)
    cls = convert_type_to_class(cls)
  end
  type_object = smart_coerce(type, enum: rules[:enum])
  prop_validate_definition!(name, cls, rules, type_object)
  # Retrive the possible underlying object with T.nilable.
  type = T::Utils::Nilable.get_underlying_type(type)
  sensitivity_and_pii = {sensitivity: rules[:sensitivity]}
  if defined?(Opus) && defined?(Opus::Sensitivity) && defined?(Opus::Sensitivity::Utils)
    sensitivity_and_pii = Opus::Sensitivity::Utils.normalize_sensitivity_and_pii_annotation(sensitivity_and_pii)
    # We check for Class so this is only applied on concrete
    # documents/models; We allow mixins containing props to not
    # specify their PII nature, as long as every class into which they
    # are ultimately included does.
    #
    if sensitivity_and_pii[:pii] && @class.is_a?(Class) && !T.unsafe(@class).contains_pii?
      raise ArgumentError.new(
        'Cannot include a pii prop in a class that declares `contains_no_pii`'
      )
    end
  end
  rules = rules.merge(
    # TODO: The type of this element is confusing. We should refactor so that
    # it can be always `type_object` (a PropType) or always `cls` (a Module)
    type: type,
    type_object: type_object,
    accessor_key: "@#{name}".to_sym,
    sensitivity: sensitivity_and_pii[:sensitivity],
    pii: sensitivity_and_pii[:pii],
    # extra arbitrary metadata attached by the code defining this property
    extra: rules[:extra]&.freeze,
  )
  validate_not_missing_sensitivity(name, rules)
  # for backcompat (the `:array` key is deprecated but because the name is
  # so generic it's really hard to be sure it's not being relied on anymore)
  if type.is_a?(T::Types::TypedArray)
    inner = T::Utils::Nilable.get_underlying_type(type.type)
    if inner.is_a?(Module)
      rules[:array] = inner
    end
  end
  rules[:setter_proc] = T::Props::Private::SetterFactory.build_setter_proc(@class, name, rules).freeze
  add_prop_definition(name, rules)
  # NB: using `without_accessors` doesn't make much sense unless you also define some other way to
  # get at the property (e.g., Chalk::ODM::Document exposes `get` and `set`).
  define_getter_and_setter(name, rules) unless rules[:without_accessors]
  if rules[:foreign] && rules[:foreign_hint_only]
    raise ArgumentError.new(":foreign and :foreign_hint_only are mutually exclusive.")
  end
  handle_foreign_option(name, cls, rules, rules[:foreign]) if rules[:foreign]
  handle_foreign_hint_only_option(name, cls, rules[:foreign_hint_only]) if rules[:foreign_hint_only]
  handle_redaction_option(name, rules[:redaction]) if rules[:redaction]
end