From d1de5d4748abc179161a40957514554e21525843 Mon Sep 17 00:00:00 2001
From: Luna Nova <git@lunnova.dev>
Date: Wed, 26 Mar 2025 18:05:55 -0700
Subject: [PATCH] lib.lists: undeprecate crossLists

mapCartesianProduct's output's order relies on the iteration order of the input attrset
encouraging picking non-meaningful names or arbitrary prefixed underscores if your usecase
requires a specific order.

See this thread for examples of clunkiness required to achieve a specific ordering.
https://discourse.nixos.org/t/lib-crosslists-is-deprecated-use-lib-cartesianproductofsets-instead/41824/10
---
 lib/lists.nix | 16 ++--------------
 1 file changed, 2 insertions(+), 14 deletions(-)

diff --git a/lib/lists.nix b/lib/lists.nix
index 3d324e545dd4..7da712c0bf4d 100644
--- a/lib/lists.nix
+++ b/lib/lists.nix
@@ -1814,7 +1814,7 @@ rec {
     => [ "13" "14" "23" "24" ]
     ```
 
-    The following function call is equivalent to the one deprecated above:
+    If you have an attrset already, consider mapCartesianProduct:
 
     ```nix
     mapCartesianProduct (x: "${toString x.a}${toString x.b}") { a = [1 2]; b = [3 4]; }
@@ -1822,19 +1822,7 @@ rec {
     ```
     :::
   */
-  crossLists = warn ''
-    lib.crossLists is deprecated, use lib.mapCartesianProduct instead.
-
-    For example, the following function call:
-
-    nix-repl> lib.crossLists (x: y: x+y) [[1 2] [3 4]]
-    [ 4 5 5 6 ]
-
-    Can now be replaced by the following one:
-
-    nix-repl> lib.mapCartesianProduct ({x,y}: x+y) { x = [1 2]; y = [3 4]; }
-    [ 4 5 5 6 ]
-  '' (f: foldl (fs: args: concatMap (f: map f args) fs) [ f ]);
+  crossLists = f: foldl (fs: args: concatMap (f: map f args) fs) [ f ];
 
   /**
     Remove duplicate elements from the `list`. O(n^2) complexity.