ivanrublev/nestru

nestru's Issues

Optional type hints

Environment

• Elixir version (elixir -v): Elixir 1.14.4 (compiled with Erlang/OTP 25)
• Nestru version (mix deps | grep nestru | head -1): nestru 0.3.3 (Hex package) (mix)

Actual behavior

Having a struct defined like:

defmodule Kratos.Models.UIContainer do
  @moduledoc false

  @derive {Nestru.Decoder, hint: %{nodes: [Kratos.Models.UINode], messages: [Kratos.Models.UIText]}}
  defstruct [
    :action,
    :method,
    :nodes,
    :messages
  ]

  @type t :: %__MODULE__{
          :action => String.t(),
          :method => String.t(),
          :nodes => [Kratos.Models.UINode.t()],
          :messages => [Kratos.Models.UIText.t()] | nil
        }
end

the messages attribute can either be a list or nil.
Currently, when messages comes back as nil from the API, I am expectedly getting a

{:error,
 %{
   get_in_keys: [#Function<8.65378251/3 in Access.key!/1>,
    #Function<8.65378251/3 in Access.key!/1>],
   message: %{message: "The first argument should be a list. Got nil instead."},
   path: ["ui", :messages]
 }}

response.

Expected behavior

Is there a way to handle optional hints? Something like

@derive {Nestru.Decoder,
           hint: %{
             nodes: [Kratos.Models.UINode],
           },
           hint_optional: %{
             messages: [Kratos.Models.UIText]
           }}

maybe.

Error when decoding empty lists from maps

Hi, thanks for your work on this library. I have been using Nestru for a while to decode maps from JSON data into Elixir structs. In the last version of Nestru (0.3.2) the library is returning an error when decoding a map that has an empty list.

Environment

• Elixir version (elixir -v): 1.14.3
• Nestru version (mix deps | grep nestru | head -1): 0.3.2

Actual behavior

Supposing we have defined the following structs:

defmodule Order do
  @derive {Nestru.Decoder, hint: %{items: [LineItem]}}

  defstruct [:id, :items]
end

defmodule LineItem do
  @derive Nestru.Decoder
  defstruct [:amount]
end

If we provide a list with LineItem values for the items field, everything works as expected:

map = %{
  "id" => "A548",
  "items" => [%{"amount" => 150}, %{"amount" => 350}]
}

{:ok, model} = Nestru.decode_from_map(map, Order)

{:ok, %Order{id: "A548", items: [%LineItem{amount: 150}, %LineItem{amount: 350}]}}

However, if we provide an empty list for the items field, an error is raised:

map = %{
  "id" => "A548",
  "items" => [],
}

{:ok, model} = Nestru.decode_from_map(map, Order)

{:error,  %{ get_in_keys: [#Function<8.75249601/3 in Access.key!/1>], message: %{message: "The first argument should be a list. Got [] instead."}, path: ["items"]}}

Expected behavior

The map should be decoded correctly, creating an Order struct with an empty list in the items field:

{:ok, %Order{id: "A548", items: []}}

Additional notes

This new error when providing empty lists appeared in version 0.3.2 of Nestru. In version 0.3.1, the expected behavior shown above occurs instead.

Polymorphic field support could be better

Thanks for your library.
For polymorphic relationships I am comparing it to polymorphic_embed with Ecto.
Nestru seems lacking because it needs explicit type hint. Consider JSON case: there are no type hints usually, but nested types could have different sets of fields, so it should be possible to match on the fields, which is what polymorphic_embed is capable of, but Nestru isn't.