change the way import-dhall works

dhallToNix.nix

@@ -1,18 +0,0 @@
-{pkgs ? import <nixpkgs> {}}: code: let
-  codeString = builtins.toString code;
-  file =
-    if builtins.isPath code
-    then code
-    else builtins.toFile "dhall-expr" codeString;
-  drv = pkgs.stdenvNoCC.mkDerivation {
-    name = "dhall-expr-as-nix";
-    src = ./.;
-    buildCommand = ''
-      cd $src
-      dhall-to-nix < ${file} > $out
-    '';
-
-    nativeBuildInputs = [pkgs.dhall-nix];
-  };
-in
-  import "${drv}" (import ./runtime.nix pkgs.lib)

flake.nix

@@ -33,7 +33,6 @@
       devShells.default = pkgs.mkShell {
         nativeBuildInputs = [self.packages.${system}.dhall self.packages.${system}.dhall-nix];
       };
-      lib.dhallToNix = import ./dhallToNix.nix {inherit pkgs;};
     })
     // {
       overlays.default = final: prev: {
@@ -44,6 +43,8 @@
               sha256 = "157x95yw9hibpifa8figawgclnc1d1bapmbp1zw60l2viy936b83";
             };
             inherit (self.packages.${prev.emptyDirectory.system}) dhall-nix-lib;
+            dhall-to-nix-package = super.callPackage ./pkgs/dhall-to-nix-package.nix {};
+            import-dhall-package = path: let drv = super.callPackage (path + "/package.nix") { buildDhallDirectoryPackage = self.dhall-to-nix-package; }; in import "${drv}" (import ./runtime.nix final.lib);
           };
         });
         inherit (self.packages.${prev.system}) dhall dhall-nix dhall-nixpkgs;

pkgs/dhall-to-nix-package.nix

@@ -0,0 +1,44 @@
+{ dhall, dhall-nix, stdenvNoCC, lndir }:
+
+{ name
+
+  # Expressions to add to the cache before interpreting the code
+, dependencies ? []
+  # The root path of the expression
+, src
+, ...
+}:
+
+let
+  cache = ".cache";
+
+  data = ".local/share";
+
+  cacheDhall = "${cache}/dhall";
+
+  dataDhall = "${data}/dhall";
+
+  sourceFile = "source.dhall";
+
+in
+  stdenvNoCC.mkDerivation {
+    name = "${name}.nix";
+    inherit src;
+    nativeBuildInputs = [lndir dhall dhall-nix];
+    buildInputs = dependencies;
+    configurePhase = ''
+    mkdir -p ${cacheDhall}
+
+    for dependency in $buildInputs; do
+      lndir -silent $dependency/${cacheDhall} ${cacheDhall}
+    done
+
+    export XDG_CACHE_HOME=$PWD/${cache}
+    '';
+    buildPhase = ''
+      cat package.dhall | dhall resolve | dhall normalize > resolved.dhall
+      '';
+    installPhase = ''
+      dhall-to-nix < resolved.dhall > $out
+    '';
+  }