gistfile1.txt

commit 08b02d4f0b70168a8032c6bc1332fecabfd8c6d0
Author: Silvan Mosberger <infinisil@icloud.com>
Date:   Wed Sep 5 09:07:57 2018 +0200

    pkgs: Add __path for attribute path

diff --git a/lib/attrsets.nix b/lib/attrsets.nix
index 1e4142562fa..8f84dfd9d8d 100644
--- a/lib/attrsets.nix
+++ b/lib/attrsets.nix
@@ -271,6 +271,25 @@ rec {
         in mapAttrs g set;
     in recurse [] set;
 
+  # Recursively adds a __path attribute to all attribute sets, corresponding to
+  # the attribute path to this value
+  mapPaths = { __path ? [], ... }@attrs:
+    if lib.isDerivation attrs then attrs
+    else lib.mapAttrs (n: v:
+      let pathSet = { __path = __path ++ [ n ]; }; in
+      if lib.isAttrs v then
+        if v ? __type && v.__type == "functionTakingPath" then v.fun (v.args // pathSet)
+        else mapPaths (v // pathSet)
+      else v
+    ) attrs;
+
+  # An attrset representing a function that takes a single argument. When it is
+  # accessed through mapPaths, it is evaluated with the argument extended with
+  # the __path argument corresponding to the path where the function was called
+  functionTakingPath = fun: args: {
+    __type = "functionTakingPath";
+    inherit args fun;
+  };
 
   /* Generate an attribute set by mapping a function over a list of
      attribute names.
diff --git a/lib/default.nix b/lib/default.nix
index c3640914405..01ce9351e98 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -69,8 +69,8 @@ let
       getAttrFromPath attrVals attrValues catAttrs filterAttrs
       filterAttrsRecursive foldAttrs collect nameValuePair mapAttrs
       mapAttrs' mapAttrsToList mapAttrsRecursive mapAttrsRecursiveCond
-      genAttrs isDerivation toDerivation optionalAttrs
-      zipAttrsWithNames zipAttrsWith zipAttrs recursiveUpdateUntil
+      mapPaths functionTakingPath genAttrs isDerivation toDerivation
+      optionalAttrs zipAttrsWithNames zipAttrsWith zipAttrs recursiveUpdateUntil
       recursiveUpdate matchAttrs overrideExisting getOutput getBin
       getLib getDev chooseDevOutputs zipWithNames zip;
     inherit (lists) singleton foldr fold foldl foldl' imap0 imap1
diff --git a/pkgs/top-level/stage.nix b/pkgs/top-level/stage.nix
index 06978d1067b..7fdfcd1f8a4 100644
--- a/pkgs/top-level/stage.nix
+++ b/pkgs/top-level/stage.nix
@@ -174,4 +174,4 @@ let
 
 in
   # Return the complete set of packages.
-  lib.fix toFix
+  lib.fix (x: lib.mapPaths (toFix x))