lib: deprecate fold (#456532)

2 files changed, 12 insertions, 13 deletions

diff --git a/lib/lists.nix b/lib/lists.nix
index a59613f06ef3..fa2a526d1602 100644
--- a/lib/lists.nix
+++ b/lib/lists.nix
@@ -9,7 +9,6 @@ let
     min
     id
     warn
-    pipe
     ;
   inherit (lib.attrsets) mapAttrs attrNames;
   inherit (lib) max;
@@ -144,10 +143,13 @@ rec {
     fold' 0;
 
   /**
-    `fold` is an alias of `foldr` for historic reasons
+    `fold` is an alias of `foldr` for historic reasons.
+
+    ::: {.warning}
+    This function will be removed in 26.05.
+    :::
   */
-  # FIXME(Profpatsch): deprecate?
-  fold = foldr;
+  fold = warn "fold has been deprecated, use foldr instead" foldr;
 
   /**
     “left fold”, like `foldr`, but from the left:
diff --git a/lib/tests/misc.nix b/lib/tests/misc.nix
index e4f2222b7685..e24ffa29d4f7 100644
--- a/lib/tests/misc.nix
+++ b/lib/tests/misc.nix
@@ -1288,25 +1288,23 @@ runTests {
     expected = [ 15 ];
   };
 
-  testFold =
+  testFoldr =
     let
-      f = op: fold: fold op 0 (range 0 100);
-      # fold with associative operator
+      f = op: foldr: foldr op 0 (range 0 100);
+      # foldr with associative operator
       assoc = f builtins.add;
-      # fold with non-associative operator
+      # foldr with non-associative operator
       nonAssoc = f builtins.sub;
     in
     {
       expr = {
         assocRight = assoc foldr;
-        # right fold with assoc operator is same as left fold
+        # foldr with assoc operator is same as foldl
         assocRightIsLeft = assoc foldr == assoc foldl;
         nonAssocRight = nonAssoc foldr;
         nonAssocLeft = nonAssoc foldl;
-        # with non-assoc operator the fold results are not the same
+        # with non-assoc operator the foldr results are not the same
         nonAssocRightIsNotLeft = nonAssoc foldl != nonAssoc foldr;
-        # fold is an alias for foldr
-        foldIsRight = nonAssoc fold == nonAssoc foldr;
       };
       expected = {
         assocRight = 5050;
@@ -1314,7 +1312,6 @@ runTests {
         nonAssocRight = 50;
         nonAssocLeft = (-5050);
         nonAssocRightIsNotLeft = true;
-        foldIsRight = true;
       };
     };