Diffo.Type.Dynamic is an Ash.Type.NewType for values whose exact type is not known until runtime. The :type field holds the Ash.Type.NewType module and :value holds the cast value.

Dynamic is limited to types that have storage_type: :map — that is, Ash.TypedStruct and Ash.Type.NewType subtypes of :struct, :map, :union, :keyword, or :tuple. Scalar Ash types such as Ash.Type.Date or Ash.Type.Decimal are not supported.

In practice, Diffo.Type.Dynamic is used as a member of Diffo.Type.Value and is not typically used as a standalone attribute type. Outstanding comparison is implemented inline via defoutstanding.

Nil handling

iex> Ash.Type.cast_input(Diffo.Type.Dynamic, nil, [])
{:ok, nil}

iex> Ash.Type.dump_to_native(Diffo.Type.Dynamic, nil, [])
{:ok, nil}

iex> Ash.Type.cast_stored(Diffo.Type.Dynamic, nil, [])
{:ok, nil}

Invalid types

Scalar Ash types and modules that are not Ash.Type.NewType with storage_type: :map are rejected at cast time:

iex> Ash.Type.cast_input(Diffo.Type.Dynamic, %Diffo.Type.Dynamic{type: Ash.Type.Date, value: ~D[2026-01-01]}, [])
{:error, "Dynamic type Ash.Type.Date must be an Ash.Type.NewType with storage_type :map"}

iex> Ash.Type.cast_input(Diffo.Type.Dynamic, %Diffo.Type.Dynamic{type: Diffo.Type.NonExistent, value: nil}, [])
{:error, "Dynamic type Diffo.Type.NonExistent must be an Ash.Type.NewType with storage_type :map"}

Checking type compatibility

Use is_valid?/1 to check whether a module is usable as a Dynamic type before constructing a %Diffo.Type.Dynamic{}:

iex> Diffo.Type.Dynamic.is_valid?(Ash.Type.Date)
false

iex> Diffo.Type.Dynamic.is_valid?(Diffo.Type.NonExistent)
false

Constraints

iex> Diffo.Type.Dynamic.dynamic_constraints(nil)
[]