From 50c33528112d26c0701ce23d435faedb89987b96 Mon Sep 17 00:00:00 2001
From: Shea Levy <shea@shealevy.com>
Date: Tue, 9 Dec 2014 08:21:36 -0500
Subject: [PATCH] builtins.readFile: realise context associated with the path

---
 src/libexpr/primops.cc | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index e7b796046..1ddeac6b2 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -756,8 +756,12 @@ static void prim_readFile(EvalState & state, const Pos & pos, Value * * args, Va
 {
     PathSet context;
     Path path = state.coerceToPath(pos, *args[0], context);
-    if (!context.empty())
-        throw EvalError(format("string ‘%1%’ cannot refer to other paths, at %2%") % path % pos);
+    try {
+        realiseContext(context);
+    } catch (InvalidPathError & e) {
+        throw EvalError(format("cannot read ‘%1%’, since path ‘%2%’ is not valid, at %3%")
+            % path % e.path % pos);
+    }
     mkString(v, readFile(path).c_str());
 }