nixpkgs/pkgs/development/beam-modules/mix-release.nix

{
  stdenv,
  lib,
  elixir,
  erlang,
  hex,
  git,
  rebar,
  rebar3,
  fetchMixDeps,
  findutils,
  ripgrep,
  bbe,
  makeWrapper,
  coreutils,
  gnused,
  gnugrep,
  gawk,
}@inputs:

{
  pname,
  version,
  src,
  nativeBuildInputs ? [ ],
  buildInputs ? [ ],
  meta ? { },
  enableDebugInfo ? false,
  mixEnv ? "prod",
  compileFlags ? [ ],
  # Build a particular named release.
  # see https://hexdocs.pm/mix/1.12/Mix.Tasks.Release.html#content
  mixReleaseName ? "",

  # Options to be passed to the Erlang compiler. As documented in the reference
  # manual, these must be valid Erlang terms. They will be turned into an
  # erlang list and set as the ERL_COMPILER_OPTIONS environment variable.
  # See https://www.erlang.org/doc/man/compile
  erlangCompilerOptions ? [ ],

  # Deterministic Erlang builds remove full system paths from debug information
  # among other things to keep builds more reproducible. See their docs for more:
  # https://www.erlang.org/doc/man/compile
  erlangDeterministicBuilds ? true,

  # Mix dependencies provided as a fixed output derivation
  mixFodDeps ? null,

  # Mix dependencies generated by mix2nix
  #
  # This assumes each dependency is built by buildMix or buildRebar3. Each
  # dependency needs to have a setup hook to add the lib path to $ERL_LIBS.
  # This is how Mix finds dependencies.
  mixNixDeps ? { },

  elixir ? inputs.elixir,
  erlang ? inputs.erlang,
  hex ? inputs.hex.override { inherit elixir; },

  # Remove releases/COOKIE
  #
  # People have different views on the nature of cookies. Some believe that they are
  # secrets, while others believe they are just ids for clustering nodes instead of
  # secrets.
  #
  # If you think cookie is secret, you can set this attr to true, then it will be
  # removed from nix store. If not, you can set it to false.
  #
  # For backward compatibility, it is set to true by default.
  #
  # You can always specify a custom cookie by using RELEASE_COOKIE environment
  # variable, regardless of the value of this attr.
  removeCookie ? true,

  # This reduces closure size, but can lead to some hard to understand runtime
  # errors, so use with caution. See e.g.
  # https://github.com/whitfin/cachex/issues/205
  # https://framagit.org/framasoft/mobilizon/-/issues/1169
  stripDebug ? false,

  ...
}@attrs:
let
  # Remove non standard attributes that cannot be coerced to strings
  overridable = builtins.removeAttrs attrs [
    "compileFlags"
    "erlangCompilerOptions"
    "mixNixDeps"
  ];
in
assert mixNixDeps != { } -> mixFodDeps == null;
assert stripDebug -> !enableDebugInfo;

stdenv.mkDerivation (
  overridable
  // {
    nativeBuildInputs =
      nativeBuildInputs
      ++
        # Erlang/Elixir deps
        [
          erlang
          elixir
          hex
          git
        ]
      ++
        # Mix deps
        (builtins.attrValues mixNixDeps)
      ++
        # other compile-time deps
        [
          findutils
          ripgrep
          bbe
          makeWrapper
        ];

    buildInputs = buildInputs;

    MIX_ENV = mixEnv;
    MIX_DEBUG = if enableDebugInfo then 1 else 0;
    HEX_OFFLINE = 1;

    DEBUG = if enableDebugInfo then 1 else 0; # for Rebar3 compilation
    # The API with `mix local.rebar rebar path` makes a copy of the binary
    # some older dependencies still use rebar.
    MIX_REBAR = "${rebar}/bin/rebar";
    MIX_REBAR3 = "${rebar3}/bin/rebar3";

    ERL_COMPILER_OPTIONS =
      let
        options = erlangCompilerOptions ++ lib.optionals erlangDeterministicBuilds [ "deterministic" ];
      in
      "[${lib.concatStringsSep "," options}]";

    LC_ALL = "C.UTF-8";

    postUnpack =
      ''
        # Mix and Hex
        export MIX_HOME="$TEMPDIR/mix"
        export HEX_HOME="$TEMPDIR/hex"

        # Rebar
        export REBAR_GLOBAL_CONFIG_DIR="$TEMPDIR/rebar3"
        export REBAR_CACHE_DIR="$TEMPDIR/rebar3.cache"

        ${lib.optionalString (mixFodDeps != null) ''
          # Compilation of the dependencies will require that the dependency path is
          # writable, thus a copy to the $TEMPDIR is inevitable here.
          export MIX_DEPS_PATH="$TEMPDIR/deps"
          cp --no-preserve=mode -R "${mixFodDeps}" "$MIX_DEPS_PATH"
        ''}
      ''
      + (attrs.postUnpack or "");

    configurePhase =
      attrs.configurePhase or ''
        runHook preConfigure

        ${./mix-configure-hook.sh}

        # This is needed for projects that have a specific compile step
        # the dependency needs to be compiled in order for the task
        # to be available.
        #
        # Phoenix projects for example will need compile.phoenix.
        mix deps.compile --no-deps-check --skip-umbrella-children

        # Symlink dependency sources. This is needed for projects that require
        # access to the source of their dependencies. For example, Phoenix
        # projects need javascript assets to build asset bundles.
        ${lib.optionalString (mixNixDeps != { }) ''
          mkdir -p deps

          ${lib.concatMapStringsSep "\n" (dep: ''
            dep_name=$(basename ${dep} | cut -d '-' -f2)
            dep_path="deps/$dep_name"
            if [ -d "${dep}/src" ]; then
              ln -s ${dep}/src $dep_path
            fi
          '') (builtins.attrValues mixNixDeps)}
        ''}

        # Symlink deps to build root. Similar to above, but allows for mixFodDeps
        # Phoenix projects to find javascript assets.
        ${lib.optionalString (mixFodDeps != null) ''
          ln -s ../deps ./
        ''}

        runHook postConfigure
      '';

    buildPhase =
      attrs.buildPhase or ''
        runHook preBuild

        mix compile --no-deps-check ${lib.concatStringsSep " " compileFlags}

        runHook postBuild
      '';

    installPhase =
      attrs.installPhase or ''
        runHook preInstall

        mix release ${mixReleaseName} --no-deps-check --path "$out"

        runHook postInstall
      '';

    postFixup =
      ''
        echo "removing files for Microsoft Windows"
        rm -f "$out"/bin/*.bat

        echo "wrapping programs in $out/bin with their runtime deps"
        for f in $(find $out/bin/ -type f -executable); do
          wrapProgram "$f" \
            --prefix PATH : ${
              lib.makeBinPath [
                coreutils
                gnused
                gnugrep
                gawk
              ]
            }
        done
      ''
      + lib.optionalString removeCookie ''
        if [ -e $out/releases/COOKIE ]; then
          echo "removing $out/releases/COOKIE"
          rm $out/releases/COOKIE
        fi
      ''
      + ''
        if [ -e $out/erts-* ]; then
          # ERTS is included in the release, then erlang is not required as a runtime dependency.
          # But, erlang is still referenced in some places. To removed references to erlang,
          # following steps are required.

          # 1. remove references to erlang from plain text files
          for file in $(rg "${erlang}/lib/erlang" "$out" --files-with-matches); do
            echo "removing references to erlang in $file"
            substituteInPlace "$file" --replace "${erlang}/lib/erlang" "$out"
          done

          # 2. remove references to erlang from .beam files
          #
          # No need to do anything, because it has been handled by "deterministic" option specified
          # by ERL_COMPILER_OPTIONS.

          # 3. remove references to erlang from normal binary files
          for file in $(rg "${erlang}/lib/erlang" "$out" --files-with-matches --binary --iglob '!*.beam'); do
            echo "removing references to erlang in $file"
            # use bbe to substitute strings in binary files, because using substituteInPlace
            # on binaries will raise errors
            bbe -e "s|${erlang}/lib/erlang|$out|" -o "$file".tmp "$file"
            rm -f "$file"
            mv "$file".tmp "$file"
          done

          # References to erlang should be removed from output after above processing.
        fi
      ''
      + lib.optionalString stripDebug ''
        # Strip debug symbols to avoid hardreferences to "foreign" closures actually
        # not needed at runtime, while at the same time reduce size of BEAM files.
        erl -noinput -eval 'lists:foreach(fun(F) -> io:format("Stripping ~p.~n", [F]), beam_lib:strip(F) end, filelib:wildcard("'"$out"'/**/*.beam"))' -s init stop
      '';
  }
)