From ef4f5ba85e487f567115d60e3cb4b53d81af6ea1 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Tue, 3 Sep 2013 13:17:51 +0000
Subject: Work on Values instead of Exprs

This prevents some duplicate evaluation in nix-env and
nix-instantiate.

Also, when traversing ~/.nix-defexpr, only read regular files with the
extension .nix.  Previously it was reading files like
.../channels/binary-caches/<name>.  The only reason this didn't cause
problems is pure luck (namely, <name> shadows an actual Nix
expression, the binary-caches files happen to be syntactically valid
Nix expressions, and we iterate over the directory contents in just
the right order).
---
 src/nix-instantiate/nix-instantiate.cc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'src/nix-instantiate')

diff --git a/src/nix-instantiate/nix-instantiate.cc b/src/nix-instantiate/nix-instantiate.cc
index 0f0710d680cb..fd2c04eae444 100644
--- a/src/nix-instantiate/nix-instantiate.cc
+++ b/src/nix-instantiate/nix-instantiate.cc
@@ -44,9 +44,11 @@ void processExpr(EvalState & state, const Strings & attrPaths,
         return;
     }
 
+    Value vRoot;
+    state.eval(e, vRoot);
+
     foreach (Strings::const_iterator, i, attrPaths) {
-        Value v;
-        findAlongAttrPath(state, *i, autoArgs, e, v);
+        Value & v(*findAlongAttrPath(state, *i, autoArgs, vRoot));
         state.forceValue(v);
 
         PathSet context;
-- 
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