@mischov: I think that this should work, but I did not fully tested it.
defmodule Type.Json do
alias Ecto.Type
@behaviour Ecto.Type
@moduledoc """
To store values that might be any json value.
Not intended as a general replacement for :map.
"""
def type, do: :json
def cast(value) when is_nil(value), do: {:ok, value}
def cast(value) when is_boolean(value), do: {:ok, value}
def cast(value) when is_binary(value), do: {:ok, value}
def cast(value) when is_number(value), do: {:ok, value}
def cast(value) when is_list(value), do: Type.cast({:array, __MODULE__}, value)
def cast(value) when is_map(value), do: Type.cast({:map, __MODULE__}, value)
def cast(_), do: :error
def load(data), do: {:ok, data}
def dump(value) when is_nil(value), do: {:ok, value}
def dump(value) when is_boolean(value), do: {:ok, value}
def dump(value) when is_binary(value), do: {:ok, value}
def dump(value) when is_number(value), do: {:ok, value}
def dump(value) when is_list(value), do: Type.dump({:array, __MODULE__}, value)
def dump(value) when is_map(value), do: Type.dump({:map, __MODULE__}, value)
def dump(_), do: :error
end
