showId: Handle empty attribute names

We should probably disallow these, but until then, we shouldn't barf
with an assertion failure.

Fixes #738.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 35db52a13acc..5bc8e4202a49 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -30,8 +30,9 @@ static void showString(std::ostream & str, const string & s)
 
 static void showId(std::ostream & str, const string & s)
 {
-    assert(!s.empty());
-    if (s == "if")
+    if (s.empty())
+        str << "\"\"";
+    else if (s == "if") // FIXME: handle other keywords
         str << '"' << s << '"';
     else {
         char c = s[0];