Fix compiler when using ERL_COMPILER_OPTIONS=deterministic #762

Activity

1. ju1m commented on Nov 25, 2025

   

   ju1m

   on Nov 25, 2025

   More actions

   The current approach assumes something more than not having ERL_COMPILER_OPTIONS=deterministic, namely that the source given by module_info still exists, which is not the case when building each mix app in ephemeral sandboxes like nix does by default.
   See in nix the source is deterministically in /build/source/, but actually exists only during the build of the mix app:

   iex(1)> Bonfire.UI.Me.Stickyheader.module_info() |> get_in([:compile])
   [
     version: ~c"9.0.2",
     options: [:no_spawn_compiler_process, :from_core, :no_core_prepare,
      :no_auto_import],
     source: ~c"/build/source/lib/components/profile/stickyheader.ex"
   ]
   

   So that by the time the dependency (Bonfire.UI.Me.Stickyheader) is used (through $ERL_LIBS), its /build/source/ is long gone (actually it's now the /build/source/ of the current mix app using that dependency).
2. ju1m commented on Nov 25, 2025

   

   ju1m

   on Nov 25, 2025

   Last edited by ju1m

   More actions

   When using nixpkgs's buildMix, a workaround is to build into $out/src/ instead of /build/source/, so that module_info returns a path inside $out, which, being the final output path of the package into the Nix store, still exists when building dependent packages:

   buildMix {
      erlangDeterministicBuilds = false;
   
      # Explanation: sadly disabling erlangDeterministicBuilds is not enough
      # for `mix compile.surface` to work across packages, as it:
      # - needs to access the content of the source path of the dependencies,
      # - and, uses as source path the actual path where the dependencies were built.
      # Since buildMix's installPhase only copies $src into $out/src,
      # that is not enough: module_info/1 will return /build/source instead of $out/src,
      # so build into $out/src, which will remain reachable after the build.
      # Issue: https://github.com/surface-ui/surface/issues/762#issuecomment-3577030748
      postUnpack = previousArgs.postUnpack or "" + ''
        mkdir -p $out
        mv $sourceRoot $out/src
        sourceRoot=$out/src
        src=$(mktemp -d)
      '';
      postInstall = previousArgs.postInstall or "" + ''
        src=$out/src
        rm -rf _build
      '';
   
     […snip…]
   }

   Which now records an existing source:, enabling compile.surface to correctly generate all the .hooks.js of the dependencies:

   iex(1)> Bonfire.UI.Me.Stickyheader.module_info() |> get_in([:compile])
   [
     version: ~c"9.0.2",
     options: [:no_spawn_compiler_process, :from_core, :no_core_prepare,
      :no_auto_import],
     source: ~c"/nix/store/xhkblhd0jnw3ynvyk66jf9cglyh2h5lb-bonfire_ui_me-0.1.0/src/lib/components/profile/stickyheader.ex"
   ]
   
3. ju1m

   added 2 commits that reference this issue on Apr 3, 2026

   beamPackages: build in $out/src and disable erlangDeterministicBuilds…

   ...

   9668fa8

   beamPackages: build in $out/src and disable erlangDeterministicBuilds…

   ...

   eede973
4. ju1m

   added a commit that references this issue on Jun 11, 2026

   beamPackages: build in $out/src

   ...

   be226f1
5. ju1m

   added 3 commits that reference this issue on Jul 17, 2026

   beamPackages: build in $out/src

   ...

   5ab752c

   beamPackages: build in $out/src

   ...

   4e1d122

   beamPackages: build in $out/src

   ...

   31c4f5e
6. ju1m

   added 2 commits that reference this issue on Aug 20, 2026

   beamPackages: build in $out/src

   ...

   6259bc1

   beamPackages.buildMix: compile non-deterministic deps in $out/src

   ...

   1b113c3