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adding mergeAttrsByFunc function - its easiy to customize how a name should be merged - the merge function is passed by the attr set itself (and can be overridden/ extended this way) This code can probably be shortened using zip and the like as proposed by Nicolas Pierron (mailinglist)

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svn path=/nixpkgs/trunk/; revision=13544
This commit is contained in:
Marc Weber 2008-12-02 12:26:36 +00:00
parent 55976c6f8d
commit 570a103136
1 changed files with 39 additions and 0 deletions
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39
pkgs/lib/default.nix
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@ -676,6 +676,45 @@ rec {
else throw "error mergeAttrsNoOverride, attribute ${n} given in both attributes - no merge func defined"
else __getAttr n attrs2 # add attribute not existing in attr1
)) attrs1 (__attrNames attrs2);
# example usage:
# mergeAttrByFunc {
# inherit mergeAttrBy; # defined below
# buildInputs = [ a b ];
# } {
# buildInputs = [ c d ];
# };
# will result in
# { mergeAttrsBy = [...]; buildInputs = [ a b c d ]; }
# is used by prepareDerivationArgs and can be used when composing using
# foldArgs, composedArgsAndFun or applyAndFun. Example: composableDerivation in all-packages.nix
mergeAttrByFunc = x : y :
let
mergeAttrBy2 = { mergeAttrBy=mergeAttr; }
// (maybeAttr "mergeAttrBy" {} x)
// (maybeAttr "mergeAttrBy" {} y); in
mergeAttrs [
x y
(mapAttrs ( a : v : # merge special names using given functions
if (__hasAttr a x)
then if (__hasAttr a y)
then v (__getAttr a x) (__getAttr a y) # both have attr, use merge func
else (__getAttr a x) # only x has attr
else (__getAttr a y) # only y has attr)
) (removeAttrs mergeAttrBy2
# don't merge attrs which are neither in x nor y
(filter (a : (! __hasAttr a x) && (! __hasAttr a y) )
(__attrNames mergeAttrBy2))
)
)
];
mergeAttrsByFunc = fold mergeAttrByFunc {};
# sane defaults (same name as attr name so that inherit can be used)
mergeAttrBy = # { buildInputs = concatList; [...]; passthru = mergeAttr; [..]; }
listToAttrs (map (n : nv n concatList) [ "buildInputs" "propagatedBuildInputs" "configureFlags" "prePhases" "postAll" ])
// listToAttrs (map (n : nv n mergeAttr) [ "passthru" "meta" ]);
# returns atribute values as a list
flattenAttrs = set : map ( attr : builtins.getAttr attr set) (attrNames set);
mapIf = cond : f : fold ( x : l : if (cond x) then [(f x)] ++ l else l) [];