`pkgxdev/dev@v1`: Elixir not working without manual `ERL_ROOTDIR` adjustment

[gaggle]

I ran into problems using pkgxdev/dev@v1 with Elixir. The workflow fails unless I add the following workaround, which sets ERL_ROOTDIR explicitly. With this in place, Elixir runs fine:

.github/actions/elixir-setup/action.yml

name: Elixir setup
description: Setup Elixir for a given path
runs:
  using: composite
  steps:
    - uses: pkgxdev/dev@v1
    - shell: bash
      run: |
        unset ERL_ROOTDIR
        ERL_BIN="$(command -v erl)"
        ERL_BIN_REAL="$(readlink -f "$ERL_BIN")"
        ERL_DIR="$(dirname "$(dirname "$ERL_BIN_REAL")")"
        if [ -d "$ERL_DIR/lib/erlang" ]; then
          ERL_BASE="$ERL_DIR/lib/erlang"
        else
          ERL_BASE="$ERL_DIR"
        fi
        echo "ERL_BASE=$ERL_BASE" >> "$GITHUB_ENV"
        echo "ERL_ROOTDIR=$ERL_BASE" >> "$GITHUB_ENV"

.github/workflows/ci.yml

name: ci
on:
  push:
    branches: main
  workflow_dispatch:
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v5
      - uses: ./.github/actions/elixir-setup
      - run: elixir -e "IO.puts(1 + 2)"

.pkgx.yaml

dependencies:
  elixir-lang.org: =1.15.6
  erlang.org: =26.1.1

Is this something that should be fixed in pkgxdev/dev@v1 itself, or is it expected that workflows need to add this step? Or does this point to something about the packages themselves?

[jhheider]

so. this works fine in a shell with dev:

jacob@illithid bar % vi pkgx.yaml
jacob@illithid bar % dev
 ✓  ~/.pkgx/elixir-lang.org/v1.15.6
 ✓  ~/.pkgx/erlang.org/v26.1.1
env +erlang.org=26.1.1 +elixir-lang.org=1.15.6
jacob@illithid bar % elixir -e 'IO.puts(1+2)'
3
jacob@illithid bar % env | grep ERL
ERL_ROOTDIR=/Users/jacob/.pkgx/erlang.org/v26.1.1/lib/erlang
jacob@illithid bar % cat pkgx.yaml
dependencies:
  elixir-lang.org: =1.15.6
  erlang.org: =26.1.1

so, what is ERL_ROOTDIR set to in your CI (both in the inner action, and in the job) if you don't modify it? it should be being set by erlang.org to:

runtime:
  env:
    ERL_ROOTDIR: ${{prefix}}/lib/erlang

it's possible there's some issue with the env propagating up from the lower action.

this:

dev/action.js

Lines 41 to 44 in 0e5d6c3

	} else {
	let v = replaceEnvVars(value);
	fs.appendFileSync(process.env["GITHUB_ENV"], `${key}=${v}\n`);
	}

, should be copying the env to the file, so adding cat $GITHUB_ENV (though, be careful if there's secret data) could also be illustrative.

[gaggle]

@jhheider good points. I've created a sample repo to illustrate the issue.

This simple pkgxdev/dev-based workflow fails:

steps:
      - uses: actions/checkout@v5
      - uses: pkgxdev/dev@v1
      - run: elixir -e "IO.puts(1 + 2)"

Error:

/home/runner/.pkgx/erlang.org/v26.1.1/bin/erl: 57: exec: ${ERL_ROOTDIR:-/home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang}/erts-14.1/bin/erlexec: not found

(via this run)

Inspecting its env shows:

ERL_ROOTDIR: ${ERL_ROOTDIR:-/home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang}

---

By contrast, a workflow that explicitly sets ERL_ROOTDIR works fine (this run, via this action):

ERL_ROOTDIR: /home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang
ERL_BASE: /home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang

I tested variations:

• Adding only ERL_BASE → still fails (run).
• Setting only ERL_ROOTDIR → works (run).

The consistent pattern seems to be: ERL_ROOTDIR must be explicitly set (is it the ${ERL_ROOTDIR:-...} defaulting that doesn’t resolve properly in CI?).

Do you think this is something pkgx or pkgxdev/dev should handle?

[gaggle]

Gentlest possible /poke @jhheider

[jhheider]

Sorry, coming back. That suggests that something else in your CI might be setting ERL_ROOTDIR, so the conditional set isn't working. It should be supported in even quite old versions of bash, and that's ubunutu 24.

Can you re-run those last two, and add a env | grep ERL_, to see how they're resolving in practice?

[gaggle]

Thanks for looking further into this @jhheider. To be sure there's no over-complications I've applied your suggestion to this simple workflow that avoids the action-pattern in favor of simple steps:

runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v5
      - uses: pkgxdev/dev@v1
      - run: cat $GITHUB_ENV
      - run: env | grep ERL_
      - run: elixir -e "IO.puts(1 + 2)"

It fails with the same error raised in this thread:

Run elixir -e "IO.puts(1 + 2)"
/home/runner/.pkgx/erlang.org/v26.1.1/bin/erl: 57: exec: ${ERL_ROOTDIR:-/home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang}/erts-14.1/bin/erlexec: not found

The env | grep step outputs:

Run env | grep ERL_
ERL_ROOTDIR=${ERL_ROOTDIR:-/home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang}

(via this run)

This avoids confusing matters with my attempts at actions and conditional logic, focusing on the core issue of pkgxdev/dev@v1 appearing to not be a able to run Elixir like how it works from my terminal.

[jhheider]

It looks like an escaping issue. The value in the env is uninterpreted. So, that's probably a dev issue. I'll take a look.

[gaggle]

Gentle ping, wonder if I can help bring more light or solutions to this?

[jhheider]

so, the problem is that it's never evalling when writing to GITHUB_ENV:

https://github.com/pkgxdev/dev/blob/main/action.js

% export ERL_ROOTDIR='${ERL_ROOTDIR:-/home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang}'
% echo $ERL_ROOTDIR ${ERL_ROOTDIR:-/home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang}
% pkgx node
Welcome to Node.js v25.1.0.
Type ".help" for more information.
> const replaceEnvVars = (str) => {
|   const value = str
|     .replaceAll(
|       /\$\{([a-zA-Z0-9_]+):\+:\$[a-zA-Z0-9_]+\}/g,
|       (_, key) => ((v) => v ? `:${v}` : "")(process.env[key]),
|     )
|     .replaceAll(/\$\{([a-zA-Z0-9_]+)\}/g, (_, key) => process.env[key] ?? "")
|     .replaceAll(/\$([a-zA-Z0-9_]+)/g, (_, key) => process.env[key] ?? "");
|   return value;
| };
undefined
> replaceEnvVars('${ERL_ROOTDIR:-/home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang}')
'${ERL_ROOTDIR:-/home/runner/.pkgx/erlang.org/v26.1.1/lib/erlang}'
>

that's being fed here: fs.appendFileSync(process.env["GITHUB_ENV"], ${key}=${v}\n);. so, it looks like the shell isn't getting an opportunity to deal with it. i think i have a fix.

[jhheider]

can you test changing your reference to: - uses: pkgxdev/dev@fix-erlang, and see if that helps?