elixir

Enable Elixir with:

languages.elixir.enable = true;

Since devenv 2.4.1, this also provides erl, erlc, and escript from the Erlang runtime used to build your selected Elixir package. Selecting a different languages.elixir.package automatically selects its matching runtime.

For custom packages that do not expose their Erlang dependency, set languages.elixir.erlang.package explicitly to the runtime used to build that package.

Choosing an Elixir version

You can pin an exact Elixir version, including release candidates, starting from 1.15.0:

languages.elixir.version = "1.17.3";

devenv selects the newest Erlang/OTP runtime that this Elixir version supports, and builds the Elixir language server with the same Elixir. Versions come from beam-overlay. To use languages.elixir.version or languages.elixir.versionFile, run the following command:

devenv inputs add beam-overlay github:zeeetech/beam-overlay --follows nixpkgs

Reading the version from a file

If your project already pins Elixir for asdf or mise, point devenv at that file:

languages.elixir.versionFile = ./.tool-versions;

devenv reads the elixir line, such as elixir 1.17.3-otp-27. A file that holds only the version, such as .elixir-version, works too. The -otp-27 part is ignored. devenv always picks the newest Erlang/OTP that the Elixir version supports.

Mix home directory

devenv sets MIX_HOME to .devenv/state/mix. Each project gets its own Hex, Rebar, archives (like phx_new) and escripts. These are built for one Elixir and Erlang/OTP version, so a shared ~/.mix can break when projects use different versions. Escripts installed with mix escript.install are on PATH.

To keep using a shared directory, set env.MIX_HOME to its full path:

env.MIX_HOME = "/home/alice/.mix";

Fetching dependencies

devenv can run mix deps.get for you when you enter the shell:

languages.elixir.mix.deps.enable = true;

It installs Hex and Rebar first if they are missing. After that, it only runs again when mix.exs, mix.lock, the Elixir package or MIX_HOME changes, or when the deps directory or Hex is gone.

If your mix.exs is not at the root of the devenv project, set languages.elixir.directory:

languages.elixir.directory = "./backend";

Options

languages.elixir.enable

Whether to enable tools for Elixir development.

Type: boolean

Default:

false

Example:

true

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix

languages.elixir.package

Which Elixir package to use.

Type: package

Default:

pkgs.beamPackages.elixir

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix

languages.elixir.directory

The Mix project’s root directory, where mix.exs lives. Defaults to the root of the devenv project. Can be an absolute path or one relative to the root of the devenv project.

Type: string

Default:

config.devenv.root

Example:

"./directory"

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix

languages.elixir.erlang.package

The Erlang runtime to include in the environment alongside Elixir. Defaults to the runtime used to build the selected Elixir package. Set this explicitly for custom packages that do not expose their Erlang dependency.

Type: package

Default:

the Erlang runtime used to build languages.elixir.package

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix

languages.elixir.lsp.enable

Whether to enable Elixir Language Server.

Type: boolean

Default:

true

Example:

true

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix

languages.elixir.lsp.package

The Elixir language server package to use.

Type: package

Default:

pkgs.beamPackages.elixir-ls.override { elixir = languages.elixir.package; }

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix

languages.elixir.mix.deps.enable

Whether to fetch Mix dependencies with mix deps.get when entering the shell. It only runs again when mix.exs, mix.lock, the Elixir package or MIX_HOME changes, or when the deps directory or Hex is missing. Hex and Rebar are installed into MIX_HOME first if they are missing.

Type: boolean

Default:

false

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix

languages.elixir.version

The Elixir version to use. This automatically sets languages.elixir.package using beam-overlay, together with the newest Erlang/OTP runtime that the version supports. Elixir 1.15.0 and newer are available, including release candidates.

Type: null or string

Default:

null

Example:

"1.17.3"

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix

languages.elixir.versionFile

A file to read the Elixir version from. This can be an asdf or mise .tool-versions file with a line like elixir 1.17.3-otp-27, or a file that holds only the version, like .elixir-version. This automatically sets languages.elixir.package using beam-overlay. The -otp-NN suffix is ignored: devenv picks the newest Erlang/OTP that the Elixir version supports.

languages.elixir.versionFile = ./.tool-versions;

Type: null or absolute path

Default:

null

Example:

./.tool-versions

Declared by:

• https://github.com/cachix/devenv/blob/main/src/modules/languages/elixir.nix