Production code is missing typespecs

[gorbak25]

Expected behavior:
Forma works in self-contained releases.

Actual behavior:
Forma is working well in the dev environment. Forma isn't working at all in compiled releases as the typespecs the library is using are stripped away during compilation. Trying to use forma in production code results in the following error:

        ** (Protocol.UndefinedError) protocol Enumerable not implemented for nil of type Atom. This protocol is implemented for the following type(s): Ecto.Adapters.SQL.Stream, Postgrex.Stream, DBConnection.Stream, DBConnection.PrepareStream, GenEvent.Stream, HashSet, Date.Range, IO.Stream, Map, File.Stream, Stream, MapSet, Range, HashDict, List, Function
            (elixir) lib/enum.ex:1: Enumerable.impl_for!/1
            (elixir) lib/enum.ex:141: Enumerable.reduce/3
            (elixir) lib/enum.ex:3023: Enum.map/2
            (forma) lib/forma/typespecs.ex:6: Forma.Typespecs.compile/1
            (forma) lib/forma/types.ex:32: Forma.Types.compile/1
            (forma) lib/forma/types.ex:23: Forma.Types.handle_call/3
            (stdlib) gen_server.erl:661: :gen_server.try_handle_call/4
            (stdlib) gen_server.erl:690: :gen_server.handle_msg/6
    (elixir) lib/gen_server.ex:1009: GenServer.call/3
    (forma) lib/forma.ex:96: Forma.parse/3

[frekw]

Hi @grzegorz225!

That sounds weird, we're using it successfully across multiple production deployments (both using mix release as well as Distillery).

Could you provide a bit more information/example code to reproduce?

[gorbak25]

@frekw Here is an minimal example which showcases the problem:
https://github.com/gorbak25/forma-bug
The demo tries to decode a simple json encoded payload each second and prints it to stdout, there is a test which tests decoding data using forma.
The tests pass and the app works correctly in both dev and prod environments - iex -S mix & MIX_ENV=prod iex -S mix

The app does not work as a compiled release:

1. mix release
2. _build/dev/rel/forma_demo/bin/forma_demo start

In the demo I'm getting the same error as in my other project.
I'm using Elixir 1.9.4 on OTP 22

[frekw]

@grzegorz225 interesting, I haven't seen that behaviour with mix release before.

Adding the following configuration keeps the typespec metadata around even when assembling a release:

  def project do
    [
      app: :forma_demo,
      version: "0.1.0",
      elixir: "~> 1.9",
      start_permanent: Mix.env() == :prod,
      deps: deps(),
      releases: [
        forma_demo: [strip_beams: false]
      ]
    ]
  end

[frekw]

See https://hexdocs.pm/mix/Mix.Tasks.Release.html#module-options for more information.