From b63f684b3d0b2e3d904ccc6348718adc7c6f93d4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20=C4=8Cun=C3=A1t?= <v@cunat.cz>
Date: Wed, 4 Mar 2020 11:58:03 +0100
Subject: [PATCH] lib.callPackages(With): guard against a repeated mistake

For example see the parent commit.
---
 lib/customisation.nix | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/customisation.nix b/lib/customisation.nix
index ac234e3b8c6f..dc5dd7691976 100644
--- a/lib/customisation.nix
+++ b/lib/customisation.nix
@@ -131,7 +131,12 @@ rec {
       origArgs = auto // args;
       pkgs = f origArgs;
       mkAttrOverridable = name: _: makeOverridable (newArgs: (f newArgs).${name}) origArgs;
-    in lib.mapAttrs mkAttrOverridable pkgs;
+    in
+      if lib.isDerivation pkgs then throw
+        ("function `callPackages` was called on a *single* derivation "
+          + ''"${pkgs.name or "<unknown-name>"}";''
+          + " did you mean to use `callPackage` instead?")
+      else lib.mapAttrs mkAttrOverridable pkgs;
 
 
   /* Add attributes to each output of a derivation without changing