lib.attrsets.foldlAttrs: Make stricter

See the parent commit for the same change to lib.lists.foldl'

lib/attrsets.nix

@@ -338,7 +338,7 @@ rec {
     );
 
    /*
-    Like builtins.foldl' but for attribute sets.
+    Like [`lib.lists.foldl'`](#function-library-lib.lists.foldl-prime) but for attribute sets.
     Iterates over every name-value pair in the given attribute set.
     The result of the callback function is often called `acc` for accumulator. It is passed between callbacks from left to right and the final `acc` is the return value of `foldlAttrs`.
 
@@ -372,9 +372,9 @@ rec {
         123
 
       foldlAttrs
-        (_: _: v: v)
-        (throw "initial accumulator not needed")
-        { z = 3; a = 2; };
+        (acc: _: _: acc)
+        3
+        { z = throw "value not needed"; a = throw "value not needed"; };
       ->
         3
 
@@ -392,7 +392,7 @@ rec {
       foldlAttrs :: ( a -> String -> b -> a ) -> a -> { ... :: b } -> a
   */
   foldlAttrs = f: init: set:
-    builtins.foldl'
+    foldl'
       (acc: name: f acc name set.${name})
       init
       (attrNames set);

lib/tests/misc.nix

@@ -740,7 +740,7 @@ runTests {
       # should just return the initial value
       emptySet = foldlAttrs (throw "function not needed") 123 { };
       # should just evaluate to the last value
-      accNotNeeded = foldlAttrs (_acc: _name: v: v) (throw "accumulator not needed") { z = 3; a = 2; };
+      valuesNotNeeded = foldlAttrs (acc: _name: _v: acc) 3 { z = throw "value z not needed"; a = throw "value a not needed"; };
       # the accumulator doesnt have to be an attrset it can be as trivial as being just a number or string
       trivialAcc = foldlAttrs (acc: _name: v: acc * 10 + v) 1 { z = 1; a = 2; };
     };
@@ -750,7 +750,7 @@ runTests {
         names = [ "bar" "foo" ];
       };
       emptySet = 123;
-      accNotNeeded = 3;
+      valuesNotNeeded = 3;
       trivialAcc = 121;
     };
   };

nixos/doc/manual/release-notes/rl-2311.section.md

@@ -229,6 +229,8 @@
 - [`lib.lists.foldl'`](https://nixos.org/manual/nixpkgs/stable#function-library-lib.lists.foldl-prime) now always evaluates the initial accumulator argument first.
   If you depend on the lazier behavior, consider using [`lib.lists.foldl`](https://nixos.org/manual/nixpkgs/stable#function-library-lib.lists.foldl) or [`builtins.foldl'`](https://nixos.org/manual/nix/stable/language/builtins.html#builtins-foldl') instead.
 
+- [`lib.attrsets.foldlAttrs`](https://nixos.org/manual/nixpkgs/stable#function-library-lib.attrsets.foldlAttrs) now always evaluates the initial accumulator argument first.
+
 - `rome` was removed because it is no longer maintained and is succeeded by `biome`.
 
 - The `services.mtr-exporter.target` has been removed in favor of `services.mtr-exporter.jobs` which allows specifying multiple targets.