From c83adb541edc7eb4729096a73ba3fae08dbb756e Mon Sep 17 00:00:00 2001
From: Minijackson <minijackson@riseup.net>
Date: Fri, 6 Oct 2023 13:35:18 +0200
Subject: [PATCH] pkgs: make package sets extensible

this enables easier overriding of packages, like this:

    nixpkgs.overlays = [
      (final: prev: {
        epnix = prev.epnix.extend (final: prev: {
          epics-base7 = prev.epics-base7.overrideAttrs (oldAttrs: {
            patches = oldAttrs.patches ++ [ ./my.patch ];
          });
        });
      })
    ];
---
 flake.nix        |  2 +-
 pkgs/default.nix | 20 ++++++++++++--------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/flake.nix b/flake.nix
index 47ed831b..88cc7953 100644
--- a/flake.nix
+++ b/flake.nix
@@ -22,7 +22,7 @@
         overlays = [overlay inputs.bash-lib.overlay];
       };
     in {
-      packages = flake-utils.lib.flattenTree (pkgs.recurseIntoAttrs pkgs.epnix);
+      packages = flake-utils.lib.flattenTree pkgs.epnix;
 
       checks =
         {
diff --git a/pkgs/default.nix b/pkgs/default.nix
index 09777425..b062816d 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -1,11 +1,15 @@
-epnixLib: final: prev:
-with prev;
-  recurseIntoAttrs rec {
+epnixLib: final: prev: let
+  inherit (final) callPackage;
+  # From prev, else it somehow causes an infinite recursion
+  inherit (prev) recurseIntoAttrs;
+  recurseExtensible = f: recurseIntoAttrs (final.lib.makeExtensible f);
+in
+  recurseIntoAttrs {
     inherit epnixLib;
 
     mkEpicsPackage = callPackage ./build-support/mk-epics-package.nix {};
 
-    epnix = recurseIntoAttrs rec {
+    epnix = recurseExtensible (self: {
       # EPICS base
 
       epics-base7 = callPackage ./epnix/epics-base {
@@ -16,11 +20,11 @@ with prev;
         version = "3.15.9";
         hash = "sha256-QWScmCEaG0F6OW6LPCaFur4W57oRl822p7wpzbYhOuA=";
       };
-      epics-base = epics-base7;
+      epics-base = self.epics-base7;
 
       # EPICS support modules
 
-      support = recurseIntoAttrs {
+      support = recurseExtensible (_self: {
         asyn = callPackage ./epnix/support/asyn {};
         autosave = callPackage ./epnix/support/autosave {};
         calc = callPackage ./epnix/support/calc {};
@@ -31,7 +35,7 @@ with prev;
         snmp = callPackage ./epnix/support/snmp {};
         sscan = callPackage ./epnix/support/sscan {};
         StreamDevice = callPackage ./epnix/support/StreamDevice {};
-      };
+      });
 
       # EPICS related tools and extensions
 
@@ -61,5 +65,5 @@ with prev;
       # EPNix specific packages
       book = callPackage ./book {};
       manpages = callPackage ./manpages {};
-    };
+    });
   }