beam27Packages.elixir : mix help failed

[ngn999]

Nixpkgs version

• Unstable (25.05)

Describe the bug

mix help

15:25:16.588 [error] beam/beam_load.c(583): Error loading function 'Elixir.Mix.Tasks.Hex.Organization':auth/2: op init y:
please re-compile this module with an Erlang/OTP 27 compiler or update your Erlang/OTP version

15:25:16.588 [error] beam/beam_load.c(583): Error loading function 'Elixir.Mix.Tasks.Hex.Owner':add_owner/4: op init y:
please re-compile this module with an Erlang/OTP 27 compiler or update your Erlang/OTP version

15:25:16.589 [error] beam/beam_load.c(583): Error loading function 'Elixir.Mix.Tasks.Hex.Registry':build/2: op init y:
please re-compile this module with an Erlang/OTP 27 compiler or update your Erlang/OTP version

15:25:16.589 [error] beam/beam_load.c(583): Error loading function 'Elixir.Mix.Tasks.Hex.Info':format_releases/2: op allocate_zero u u:
please re-compile this module with an Erlang/OTP 27 compiler or update your Erlang/OTP version

Steps to reproduce

Expected behaviour

mix help should print normal info.

Screenshots

No response

Relevant log output

Additional context

beam26Packages.elixir works.

System metadata

• system: "aarch64-darwin"
• host os: Darwin 24.3.0, macOS 15.3.2
• multi-user?: yes
• sandbox: no
• version: nix-env (Nix) 2.24.11
• channels(root): "nixpkgs"
• nixpkgs: /nix/store/dbg8dsy231ckdqdz6hjwzmp9cfa6bfqf-source

Notify maintainers

@ankhers @sgiath

Note for maintainers: Please tag this issue in your pull request description. (i.e. Resolves #ISSUE.)

I assert that this issue is relevant for Nixpkgs

• I assert that this is a bug and not a support request.
• I assert that this is not a duplicate of an existing issue.
• I assert that I have read the NixOS Code of Conduct and agree to abide by it.

Is this issue important to you?

Add a 👍 reaction to issues you find important.

[ankhers]

This is not a bug. This is just how Elixir/Erlang works. Simply run

$ mix local.hex

and it will fix this for you.

---

The reason this happens is that mix uses archives in order to provide you with some amount of functionality. One of these is the interface to hex, which is where you are seeing this error. And, at least by default, mix will install these archives globally.

What is happening is that you previously used a different version of Erlang in order to originally compile the hex archive. Now that you changed Erlang versions, you just need to recompile the package.

An alternative would be to install these archives per project to avoid this type of issue. You can specify the MIX_ARCHIVES environment variable to tell mix where to install these archives. The default location is ~/.mix/archives (https://hexdocs.pm/mix/Mix.html#module-environment-variables).

[ngn999]

Thanks.
You are right.