How to install Erlang or Elixir with Observer using the Nix package manager?

Question

Every time I install Erlang, I end up without Observer. Used the commands below on a Ubuntu laptop with Xmonad and a Debian 9 running in the cloud , and seemingly they both resulted in the same package being installed:

• nix-env -iA pkgs.beam.packages.erlangR22
• nix-env -iA nixpkgs.beam.interpreters.erlang
• nix-env -iA nixpkgs.beam.interpreters.erlangR22_odbc_javac

The Nixpkgs manuals 15.2. BEAM Languages (Erlang, Elixir & LFE) section (Version 19.09.1484.84586a4514d) does not mention Observer at all. It has a fairly recent update by DianaOlympos that does mention it, albeit I tried all these packages, but no joy:

Many Erlang/OTP distributions available in beam.interpreters have versions with ODBC and/or Java enabled or without wx (no observer support). For example, there's beam.interpreters.erlangR22_odbc_javac , which corresponds to beam.interpreters.erlangR22 and beam.interpreters.erlangR22_nox , which corresponds to beam.interpreters.erlangR22 .

Shane Sveller pointed it out that the wxGTK package needs to be set up using propagatedBuildInputs , but not sure how to do that. (Simply just installing wxGTK then Erlang doesn't work of course; was naive enough to try it. Also found out that chapter 20 of Nix Pills is exactly about this topic.)

This is also kind of a follow-up to the question " How to install Erlang/Elixir on a non-NixOS system? ", but I didn't realize it then that Observer is missing...

---

update: Apparently, it works somewhere out of the box . (Probably on NixOS.)

Answer 1

I have an overwrite for erlang, such that wx support is enabled:

{ pkgs ? import <nixpkgs> {} }:

with pkgs;

let
  inherit (lib) optionals;

  erlang_wx = erlangR21.override {
    wxSupport = true;
  };

  elixir = (beam.packagesWith erlang_wx).elixir.override {
    version = "1.9.2";
    rev = "ffe7a577cc80f37381dc289c820842d346002364";
    sha256 = "19yn6nx6r627f5zbyc7ckgr96d6b45sgwx95n2gp2imqwqvpj8wc";
  };
in

mkShell {
  buildInputs = [ elixir git ]

    # For file_system on Linux.
    ++ optionals stdenv.isLinux [ inotify-tools wxGTK ]

    # For file_system on macOS.
    ++ optionals stdenv.isDarwin (with darwin.apple_sdk.frameworks; [
      # For file_system on macOS.
      CoreFoundation
      CoreServices
      wxmac
    ]);
}

Save this (as shell.nix for example), and just run it:

$ nix-shell shell.nix

# or, if you are in the same directory:
$ nix-shell

Works on my machine!

---

Note: wxmac in buildInputs is specific to MacOS (and wxGTK to Linux). To find the right package for your OS, here are the available wx packages .

Answer 2

Kind of ashamed to admit that I am an idiot, but Observer was there all this time ( along with net_adm )...

For some reason, it wouldn't autocomplete on the erl shell, but once observer:start(). was typed in and executed, it would recognize the module, and provide a list of available functions when hitting the Tab key.

I probably messed up translating between iex and erl ( observer.start(). and other combinations), and I assumed that the resulting error message (together with no autocompletion) means that the module was missing.