From 596b3663a53de13a7f56d0b052c094214fbad49d Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Sat, 30 Apr 2022 12:57:50 +0200
Subject: [PATCH] pkgs/top-level/config.nix: Add warnUndeclaredOptions

---
 pkgs/top-level/config.nix  | 16 +++++++++++++++-
 pkgs/top-level/default.nix |  6 ++----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/pkgs/top-level/config.nix b/pkgs/top-level/config.nix
index d553b624039e..ae132d69a4e9 100644
--- a/pkgs/top-level/config.nix
+++ b/pkgs/top-level/config.nix
@@ -1,6 +1,6 @@
 # This file defines the structure of the `config` nixpkgs option.
 
-{ lib, ... }:
+{ config, lib, ... }:
 
 with lib;
 
@@ -28,6 +28,11 @@ let
 
     /* Config options */
 
+    warnUndeclaredOptions = mkOption {
+      description = "Whether to warn when <literal>config</literal> contains an unrecognized attribute.";
+      default = false;
+    };
+
     doCheckByDefault = mkMassRebuild {
       feature = "run <literal>checkPhase</literal> by default";
     };
@@ -113,6 +118,15 @@ let
 
 in {
 
+  freeformType =
+    let t = lib.types.attrsOf lib.types.raw;
+    in t // {
+      merge = loc: defs:
+        lib.mapAttrs
+          (k: v: lib.warnIf config.warnUndeclaredOptions "undeclared Nixpkgs option set: config.${k}" v)
+          (t.merge loc defs);
+    };
+
   inherit options;
 
 }
diff --git a/pkgs/top-level/default.nix b/pkgs/top-level/default.nix
index e95a0db78c3c..b32aabc3a1fd 100644
--- a/pkgs/top-level/default.nix
+++ b/pkgs/top-level/default.nix
@@ -79,15 +79,13 @@ in let
       ./config.nix
       ({ options, ... }: {
         _file = "nixpkgs.config";
-        # filter-out known options, FIXME: remove this eventually
-        config = builtins.intersectAttrs options config1;
+        config = config1;
       })
     ];
   };
 
   # take all the rest as-is
-  config = lib.showWarnings configEval.config.warnings
-    (config1 // builtins.removeAttrs configEval.config [ "_module" ]);
+  config = lib.showWarnings configEval.config.warnings configEval.config;
 
   # A few packages make a new package set to draw their dependencies from.
   # (Currently to get a cross tool chain, or forced-i686 package.) Rather than