try to split out package

flake.nix

@@ -13,20 +13,7 @@
       with nixpkgs.legacyPackages.${system}; {
         packages =
         {
-          default = 
-            rustPlatform.buildRustPackage {
-              name = "${productName}";
-              version = "${productVersion}";
-
-              src = lib.cleanSource ./.;
-
-              cargoSha256 = "sha256-d84QNj9SIRUwtlsa9sdYKuYf0oCptdGm7pDs3eGTcBg=";
-
-              preConfigure = ''
-                export LIBCLANG_PATH="${llvmPackages.libclang.lib}/lib";
-              '';
-              nativeBuildInputs = [ cargo clang cmake ];
-            };
+          default = import ./package.nix
         };
   
         devShells.default = mkShell {

module.nix

@@ -43,6 +43,7 @@ let
   };
 
   # config.services.blockstream-electrs = config.services.blockstream-electrs;
+  myPackage = import ./package.nix;
   nbLib = config.nix-bitcoin.lib;
   secretsDir = config.nix-bitcoin.secretsDir;
   bitcoind = config.services.bitcoind;
@@ -77,7 +78,7 @@ in {
         # electrs only uses the working directory for reading electrs.toml
         WorkingDirectory = config.services.blockstream-electrs.dataDir;
         ExecStart = ''
-          ${config.pkgs.blockstream-electrs}/bin/electrs \
+          ${myPackage}/bin/electrs \
           --log-filters=INFO \
           --network=${bitcoind.makeNetworkName "bitcoin" "regtest"} \
           --db-dir='${config.services.blockstream-electrs.dataDir}' \

package.nix

@@ -0,0 +1,15 @@
+{config, pkgs, lib, ...}:
+
+rustPlatform.buildRustPackage {
+  name = "${productName}";
+  version = "${productVersion}";
+
+  src = lib.cleanSource ./.;
+
+  cargoSha256 = "sha256-d84QNj9SIRUwtlsa9sdYKuYf0oCptdGm7pDs3eGTcBg=";
+
+  preConfigure = ''
+    export LIBCLANG_PATH="${llvmPackages.libclang.lib}/lib";
+  '';
+  nativeBuildInputs = [ cargo clang cmake ];
+}