Phoenix: (UndefinedFunctionError) function Poison.decode!/1 is undefined (module Poison is not available)

[GildedHonour]

recently I've begun getting plenty of errors in the console:

[error] Ranch protocol #PID<0.680.0> of listener MyAppWeb.Endpoint.HTTP (cowboy_clear) terminated
** (exit) an exception was raised:
    ** (UndefinedFunctionError) function Poison.decode!/1 is undefined (module Poison is not available)
        Poison.decode!("[\"3\",\"3\",\"phoenix:live_reload\",\"phx_join\",{}]")
        (phoenix) lib/phoenix/socket/serializers/v2_json_serializer.ex:30: Phoenix.Socket.V2.JSONSerializer.decode!/2
        (phoenix) lib/phoenix/transports/websocket.ex:126: Phoenix.Transports.WebSocket.ws_handle/3
        (phoenix) lib/phoenix/endpoint/cowboy2_websocket.ex:44: Phoenix.Endpoint.Cowboy2WebSocket.websocket_handle/2
        (cowboy) /home/user_123/my_app/deps/cowboy/src/cowboy_websocket.erl:454: :cowboy_websocket.handler_call/6
        (cowboy) /home/user_123/my_app/deps/cowboy/src/cowboy_http.erl:201: :cowboy_http.loop/2
        (stdlib) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

mix

  defp deps do
    [
      {:phoenix, github: "phoenixframework/phoenix", override: true},
      {:phoenix_pubsub, "~> 1.0"},
      {:phoenix_ecto, "~> 3.3"},
      {:postgrex, "~> 0.13.5"},
      {:phoenix_html, "~> 2.11"},
      {:phoenix_live_reload, "~> 1.1", only: :dev},
      {:gettext, "~> 0.15.0"},
      {:cowboy, "~> 2.4", override: true},
      {:yamerl, "~> 0.7.0"},
      {:earmark, "~> 1.2"},
      {:edeliver, "~> 1.5"},
      {:distillery, "~> 1.5"},
      {:httpoison, "~> 1.1"},
      {:swoosh, "~> 0.15"},
      {:gen_smtp, "~> 0.12.0"}
    ]
  end

[wojtekmach]

I think the reason is you had a project generated before 1.4-dev and now that you depend on master you'll need to do the following:

1. add {:jason, "~> 1.0"}, to your mix.exs deps
2. add config :phoenix, :json_library, Jason to your config/config.exs

and you should be good to go. You can of course still use Poison, but Jason is recommended and is the default for new 1.4 projects.

[GildedHonour]

Didn't work, the error remained. Adding poison in dependencies - worked.

El 14 de julio de 2018 1:24:44 GMT+07:00, Wojtek Mach [e-mail] escribió:

I think the reason is you had a project generated before 1.4-dev and
now that you depend on master you'll need to do the following:

1. add {:jason, "~> 1.0"}, to your mix.exs deps
2. add config :phoenix, :json_library, Jason to your
   config/config.exs

and you should be good to go. You can of course still use Poison, but
Jason is recommended and is the default for new 1.4 projects.

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[chrismccord]

As @wojtekmach said, 1.4 promotes Jason as the default encoder and following his steps should work but you may need to mix clean first. Phoenix also falls back to Poison if no configuration has been set, which requires Poison in your deps. We will be sure to highlight these changes in the upgrade guide. Thanks!

[GildedHonour]

I know what he said. And I said - that didn't work.

[venkatvb]

Thanks @wojtekmach @chrismccord. It worked for me 👍

[sir-ko]

I'm running into the same issue, but as @GildedHonour already mentioned: adding poison in dependencies works for now. Thanks

[spinlock99]

I just updated phoenix_swagger and started getting this error. My project was created post 1.4 so I already have the Json configured in mix.exs and config.exs.

To fix the issue I had to add:

{:poison, "~> 3.1"}

to my deps in mix.exs