From 3c6b8a521561f5341652ffe37b869d5ab457227b Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Mon, 2 Jun 2014 17:58:43 +0200
Subject: [PATCH] nix-env -qa --json: Generate valid JSON even if there are
 invalid meta attrs

---
 src/nix-env/nix-env.cc | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index 2d38f2aea7..05f6aa3549 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -882,9 +882,10 @@ static void queryJSON(Globals & globals, vector<DrvInfo> & elems)
         foreach (StringSet::iterator, j, metaNames) {
             metaObj.attr(*j);
             Value * v = i->queryMeta(*j);
-            if (!v)
+            if (!v) {
                 printMsg(lvlError, format("derivation `%1%' has invalid meta attribute `%2%'") % i->name % *j);
-            else {
+                cout << "null";
+            } else {
                 PathSet context;
                 printValueAsJSON(globals.state, true, *v, cout, context);
             }