Import all subfiles of a bazel local cache (content-addressable hash for each artifact) into the nix store, one derivation each

importBazelLocalCache.nix

{ nixpkgs ? import <nixpkgs> {} }:
let
  inherit (nixpkgs) lib;

  importBazelLocalCache = cacheDir:
    let
      fileList = lib.mapAttrs
        (dirname: type:
          # sanity check
          assert lib.assertMsg (type == "directory" || type == "regular")
            "${dirname} is of type ${type}, which is not supported";
          # prepend cache dir
          builtins.path { path = cacheDir + ("/" + dirname); })
        (builtins.readDir cacheDir);
    in
      nixpkgs.runCommand "bazel-cache" {} (''
        mkdir $out
      ''
      + (lib.concatStringsSep "\n"
          (lib.mapAttrsToList
            (dirname: path:
              "ln -s ${lib.escapeShellArg path} " # <- space
                   + "$out/${lib.escapeShellArg dirname}")
             fileList)));

in
  importBazelLocalCache