make cache dir configurable

example/flake.nix

@@ -20,6 +20,7 @@
 
       perSystem = { config, pkgs, ... }: {
         deno-with-packages.lockfiles = [ ./deno.lock ];
+        deno-with-packages.dir = "$FLAKE_ROOT/.deno_cache";
 
         devShells.default = pkgs.mkShell {
           inputsFrom = [ config.flake-root.devShell ];

flake-module.nix

@@ -41,6 +41,7 @@ in
             default = impl.denoWithCache {
               baseDeno = config.deno-with-packages.basePackage;
               sharedCache = config.deno-with-packages.cache;
+              dir = config.deno-with-packages.dir;
             };
           };
 

impl.nix

@@ -109,16 +109,12 @@ EOF
       '';
 
   denoWithCache =
-    { baseDeno, sharedCache }:
+    { baseDeno, sharedCache, dir }:
     pkgs.writeShellScriptBin "deno" ''
       set -euo pipefail
 
-      if [ -n "''${FLAKE_ROOT:-}" ]; then
-        CACHE_DIR="$FLAKE_ROOT/.deno_cache"
-      else
-        echo "FLAKE_ROOT not set. Make sure you're using the flake-root devShell." >&2
-        exit 1
-      fi
+      # Use configured dir, with support for FLAKE_ROOT variable expansion
+      CACHE_DIR="${dir}"
 
       if [ ! -d "$CACHE_DIR" ] || [ ! "$(ls -A "$CACHE_DIR" 2>/dev/null)" ]; then
         echo "Setting up Deno cache at: $CACHE_DIR" >&2