From 9cd9d8fe3cca6b03618ca3a7014f55f63983737f Mon Sep 17 00:00:00 2001
From: Wroclaw <wroclaw223@outlook.com>
Date: Mon, 17 Jun 2024 07:40:18 +0200
Subject: [PATCH] pkgs/overlay: create selfExpr

adds a package that references nixpkgs
config of nixpkgs that created it is retained
---
 pkgs/overlays/selfExpr.nix | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 pkgs/overlays/selfExpr.nix

diff --git a/pkgs/overlays/selfExpr.nix b/pkgs/overlays/selfExpr.nix
new file mode 100644
index 0000000..391f32c
--- /dev/null
+++ b/pkgs/overlays/selfExpr.nix
@@ -0,0 +1,21 @@
+{ nixpkgsPath ? <nixpkgs> }:
+
+self: super: {
+  selfExpr = let
+    config = builtins.removeAttrs self.config [ "_undeclared" ];
+    configJson = builtins.toJSON config;
+  in
+    self.writeTextFile {
+    name = "nixpkgs-self";
+    destination = "/default.nix";
+    text = ''
+      { ... } @ args:
+
+      import ${builtins.toString nixpkgsPath} {
+        config = (builtins.fromJSON '''
+          ${configJson}
+        ''') // args.config or {};
+      } // builtins.removeAttrs args [ "config" ]
+    '';
+  };
+}