nix-env: Load files in ~/.nix-defexpr on demand

So if you do "nix-env -qa -A nixos", then other channels won't be
parsed/evaluated at all.

2 files changed, 12 insertions, 0 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 50f36ce4e90b..af2bf92e3fe9 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -222,6 +222,12 @@ void EvalState::addPrimOp(const string & name,
 }
 
 
+void EvalState::getBuiltin(const string & name, Value & v)
+{
+    v = *baseEnv.values[0]->attrs->find(symbols.create(name))->value;
+}
+
+
 /* Every "format" object (even temporary) takes up a few hundred bytes
    of stack space, which is a real killer in the recursive
    evaluator.  So here are some helper functions for throwing
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 29c8341dfb9a..b08bec8d9eb9 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -203,6 +203,12 @@ private:
     void addPrimOp(const string & name,
         unsigned int arity, PrimOpFun primOp);
 
+public:
+
+    void getBuiltin(const string & name, Value & v);
+
+private:
+
     inline Value * lookupVar(Env * env, const VarRef & var, bool noEval);
 
     friend class ExprVar;