Implementing a fix allowing deepOverride without changing dependency-tree-leaf packages

svn path=/nixpkgs/trunk/; revision=22533

2 files changed, 6 insertions, 2 deletions

diff --git a/pkgs/lib/attrsets.nix b/pkgs/lib/attrsets.nix
index c19033682919c..f39b46db62138 100644
--- a/pkgs/lib/attrsets.nix
+++ b/pkgs/lib/attrsets.nix
@@ -270,4 +270,9 @@ rec {
       else eqStrict pat val
     ) [pattern attrs]));
 
+  # override only the attributes that are already present in the old set
+  # useful for deep-overriding
+  overrideExisting = old: new:
+  old // listToAttrs (map (attr: nameValuePair attr (attrByPath [attr] (getAttr attr old) new)) (attrNames old));
+
 }
diff --git a/pkgs/lib/customisation.nix b/pkgs/lib/customisation.nix
index 177856e4d0ef3..41af26edae703 100644
--- a/pkgs/lib/customisation.nix
+++ b/pkgs/lib/customisation.nix
@@ -53,11 +53,10 @@ rec {
     { override = newArgs:
         makeOverridable f (origArgs // (if builtins.isFunction newArgs then newArgs origArgs else newArgs));
       deepOverride = newArgs:
-        makeOverridable f ((lib.mapAttrs (deepOverrider newArgs) origArgs) // newArgs);
+        makeOverridable f (lib.overrideExisting (lib.mapAttrs (deepOverrider newArgs) origArgs) newArgs);
       origArgs = origArgs;
     };
 
-
   deepOverrider = newArgs: name: x: if builtins.isAttrs x then (
     if x ? deepOverride then (x.deepOverride newArgs) else
     if x ? override then (x.override newArgs) else