`apply_changes/1` does not convert nested schemaless validation changeset

Elixir version

1.16.3

Database and Version

13.16

Ecto Versions

3.12.3

Database Adapter and Versions (postgrex, myxql, etc)

0.19.1

Current behavior

Sometimes it's useful to validate maps without a schema, to avoid having to define another embedded struct or to do dynamic validations:

defmodule MySchema do
  use Ecto.Schema
  import Ecto.Changeset

  @primary_key false
  embedded_schema do
    field :extended, :map
  end

  def changeset(struct \\ %__MODULE__{}, params) do
    struct
    |> cast(params, [:extended])
    |> update_change(:extended, fn extended ->
      {%{}, %{foo: :integer, bar: :integer}}
      |> cast(extended || %{}, [:foo, :bar])
      |> validate_required([:bar])
    end)
  end
end

test "apply_changes/1 for nested schemaless changeset" do
  params = %{"extended" => %{"foo" => 1, "bar" => 2}}
  changeset = MySchema.changeset(%MySchema{}, params)

  %MySchema{extended: %{foo: 1, bar: 2}} = apply_changes(changeset)
end

Expected behavior

apply_changes/1 should convert the nested changeset to a map with atom keys.

elixir-ecto / ecto

`apply_changes/1` does not convert nested schemaless validation changeset #4514