Add deepSeq lib function

pkgs/lib/attrsets.nix

@@ -5,7 +5,7 @@ with {
   inherit (import ./trivial.nix) or;
   inherit (import ./default.nix) fold;
   inherit (import ./strings.nix) concatStringsSep;
-  inherit (import ./lists.nix) concatMap concatLists all;
+  inherit (import ./lists.nix) concatMap concatLists all deepSeqList;
   inherit (import ./misc.nix) maybeAttr;
 };
 
@@ -314,4 +314,5 @@ rec {
   overrideExisting = old: new:
     old // listToAttrs (map (attr: nameValuePair attr (attrByPath [attr] (getAttr attr old) new)) (attrNames old));
 
+  deepSeqAttrs = x: y: deepSeqList (attrValues x) y;
 }

pkgs/lib/lists.nix

@@ -1,4 +1,7 @@
 # General list operations.
+with {
+  inherit (import ./trivial.nix) deepSeq;
+};
 
 rec {
   inherit (builtins) head tail length isList add sub lessThan;
@@ -220,4 +223,5 @@ rec {
       ++ zipTwoLists (tail xs) (tail ys)
     else [];
 
+  deepSeqList = xs: y: if any (x: deepSeq x false) xs then y else y;
 }

pkgs/lib/trivial.nix

@@ -1,3 +1,8 @@
+with {
+  inherit (import ./lists.nix) deepSeqList;
+  inherit (import ./attrsets.nix) deepSeqAttrs;
+};
+
 rec {
 
   # Identity function.
@@ -22,4 +27,10 @@ rec {
   # evaluation of its first argument.
   seq = x: y: if x == null then y else y;
   
+  deepSeq = x: y:
+    if builtins.isList x
+      then deepSeqList x y
+    else if builtins.isAttrs x
+      then deepSeqAttrs x y
+      else seq x y;
 }