Helper module for more ergonomic ecto model json encoding

ecto_json_encoder.ex

defmodule EctoEncoder do
  def encode(struct, opts \\ []) do
    struct
    |> Map.from_struct
    |> (fn x -> if opts[:take] !== nil, do: Map.take(x, opts[:take]), else: x end).()
    |> Map.drop([:__meta__|(opts[:drop] || [])])
    |> Enum.reduce(%{}, fn
      {_, %Ecto.Association.NotLoaded{}}, acc -> acc
      {key, value}, acc -> Map.put(acc, key, value)
    end)
  end

  defmacro generate_encoder(encoder_opts \\ []) do
    quote do
      defimpl Jason.Encoder, for: __MODULE__ do
        def encode(x, opts), do: EctoEncoder.encode(x, unquote(encoder_opts)) |> Jason.Encoder.encode(opts)
      end
    end
  end

  defmacro generate_encoder_for(module, encoder_opts \\ []) do
    quote do
      defimpl Jason.Encoder, for: unquote(module) do
        def encode(x, opts), do: EctoEncoder.encode(x, unquote(encoder_opts)) |> Jason.Encoder.encode(opts)
      end
    end
  end
end