pnpm.fetchDeps: add serve script

This script allows users to reuse the cached dependencies outside of
derivations.

Signed-off-by: Sefa Eyeoglu <contact@scrumplex.net>
(cherry picked from commit 728d48285e)

pkgs/development/tools/pnpm/fetch-deps/default.nix

@@ -1,6 +1,7 @@
 {
   stdenvNoCC,
   fetchurl,
+  callPackage,
   jq,
   moreutils,
   cacert,
@@ -29,7 +30,7 @@
             outputHashAlgo = "sha256";
           };
     in
-    stdenvNoCC.mkDerivation (
+    stdenvNoCC.mkDerivation (finalAttrs: (
       args'
       // {
         name = "${pname}-pnpm-deps";
@@ -69,12 +70,19 @@
           runHook postFixup
         '';
 
+        passthru = {
+          serve = callPackage ./serve.nix {
+            inherit pnpm;
+            pnpmDeps = finalAttrs.finalPackage;
+          };
+        };
+
         dontConfigure = true;
         dontBuild = true;
         outputHashMode = "recursive";
       }
       // hash'
-    );
+    ));
 
   configHook = makeSetupHook {
     name = "pnpm-config-hook";

pkgs/development/tools/pnpm/fetch-deps/serve.nix

@@ -0,0 +1,30 @@
+{ writeShellApplication, pnpm, pnpmDeps }:
+writeShellApplication {
+  name = "serve-pnpm-store";
+
+  runtimeInputs = [
+    pnpm
+  ];
+
+  text = ''
+    storePath=$(mktemp -d)
+
+    clean() {
+      echo "Cleaning up temporary store at '$storePath'..."
+
+      rm -rf "$storePath"
+    }
+
+    echo "Copying pnpm store '${pnpmDeps}' to temporary store..."
+
+    cp -Tr "${pnpmDeps}" "$storePath"
+    chmod -R +w "$storePath"
+
+    echo "Run 'pnpm install --store-dir \"$storePath\"' to install packages from this store."
+
+    trap clean EXIT
+
+    pnpm server start \
+      --store-dir "$storePath"
+  '';
+}