Add ReleaseRuntimeProvider for exs config at runtime

[kloenk]

Changes

This lets the user define elixir code as config.

I plane to use this in my approach for OIDC as with this the config can easily define functions to apply roles base on claims in the token.

Tests

• Automated tests have been added
• This PR does not require tests

Changelog

• Entry has been added to changelog
• This PR does not make a user-facing change
  At this time the config is just an extra way to configure, so the user does not yet have to be aware of it.

Documentation

• Docs have been updated
• This change does not need a documentation update

Dark mode

• The UI has been tested both in dark and light mode
• This PR does not change the UI

[ruslandoga]

👋 @kloenk

I think this should be already possible by mounting a custom config/runtime.exs

$ docker run --rm -t ghcr.io/ruslandoga/analytics:my-build ls releases/0.0.1
consolidated        iex                 runtime.exs         start_clean.boot    vm.args
elixir              plausible.rel       start.boot          start_clean.script
env.sh              remote.vm.args      start.script        sys.config
$ docker run --rm -t ghcr.io/ruslandoga/analytics:my-build head releases/0.0.1/runtime.exs
import Config
import Plausible.ConfigHelpers
require Logger

if config_env() in [:dev, :test] do
  Envy.load(["config/.env.#{config_env()}"])
end

if config_env() == :small_dev do
  Envy.load(["config/.env.dev"])
$ docker run --rm -t -v ./config.exs:/app/releases/0.0.1/runtime.exs ghcr.io/ruslandoga/analytics:my-build head releases/0.0.1/runtime.exs
import Config

raise "oops"
$ docker run --rm -t -v ./config.exs:/app/releases/0.0.1/runtime.exs ghcr.io/ruslandoga/analytics:my-build
ERROR! Config provider Config.Reader failed with:
** (RuntimeError) oops
    /app/releases/0.0.1/runtime.exs:3: (file)
    (elixir 1.16.0) src/elixir.erl:405: :elixir.eval_external_handler/3
    (stdlib 5.2) erl_eval.erl:750: :erl_eval.do_apply/7
    (elixir 1.16.0) src/elixir.erl:378: :elixir.eval_forms/4
    (elixir 1.16.0) lib/module/parallel_checker.ex:112: Module.ParallelChecker.verify/1
    (elixir 1.16.0) lib/code.ex:568: Code.validated_eval_string/3
    (elixir 1.16.0) lib/config.ex:290: Config.__eval__!/3
    (elixir 1.16.0) lib/config/reader.ex:92: Config.Reader.read!/2

[kloenk]

As I don't use docker and my package gets installed into a immutable place (nix) this is less convenient. So the approach in this PR would be favorable for me, but I could work around it as well.

[ruslandoga]

Right, I think allowing extra config might be a useful escape hatch for the configurations not covered by the current env vars (like #3799). I explored a bit and it seems like it isn't necessary to implement a custom config reader. The default one could be reused and there are multiple ways to do it, here's the approach I like:

1. we would add an intermediary config that allows import

_mix.exs

  defp releases do
    [
      plausible: [
        config_providers: [
          {Config.Reader, path: {:system, "RELEASE_ROOT", "/import_config.exs"}, imports: []}
        ]
      ]
    ]
  end

2. we would check for an env var like EXTRA_CONFIG_PATH and conditionally import another config

_{rel/overlays/import_config.exs}

import Conifg

if extra_config_path = System.get_env("EXTRA_CONFIG_PATH") do
  import_config extra_config_path
end

PR: #3906

[ruslandoga]

I'm going to close this as #3906 has been merged.

[ruslandoga]

@kloenk thank you!