README

A set of Nix tools to work with Elixir's Phoenix web framework, with Elixir 12 and Phoenix 1.6. The goal is reproducible builds, but we also get virtual environments with this setup. For example, one could replace asdf with nix shells.

Elixir 12 and Phoenix 1.6 bring some important changes. For Nix users, the most important is probably switching out webpack for esbuild to handle front end dependencies, meaning no dependency on Node.js and no additional setup required when compiling a Phoenix app. A big win for reproducibility.

The phx-shell.nix is standalone, and should be modified to work with the flake.nix expression.

An example workflow might look something like this:

• pop into a Nix shell (especially if you're using a different Elixir version): nix-shell phx-shell.nix. You're now in an environment which specifies Elixir 12 and sets up some env vars you would expect, the mix2nix tool for handling Mix dependencies in Nix, and the mix phx.new task for generating Phoenix projects.
• set up your Phoenix project as you usually would: mix phx.new my-project.
• copy the flake.nix and shell.nix files into your project directory.
• Notice that the flake imports a deps.nix file, which doesn't exist yet. This is where mix2nix comes in: run mix2nix > deps.nix. This will look at your mix.lock file, query hex for the dependency binaries, and add them to the nix store. Now your environment and your build will query the nix store instead of fetching dependencies externally.
• You can now run nix build to build a Mix release (which will be under result/bin/my-project-name) or hack on the project further with nix develop. Check out the flake docs for more commands.