Support quoted attribute names in -A

This is requires if you have attribute names with dots in them.  So
you can now say:

  $ nix-instantiate '<nixos>' -A 'config.systemd.units."postgresql.service".text' --eval-only

Fixes #151.

1 files changed, 34 insertions, 10 deletions

diff --git a/src/libexpr/attr-path.cc b/src/libexpr/attr-path.cc
index 737166435e39..4f28a549f035 100644
--- a/src/libexpr/attr-path.cc
+++ b/src/libexpr/attr-path.cc
@@ -6,23 +6,44 @@
 namespace nix {
 
 
+static Strings parseAttrPath(const string & s)
+{
+    Strings res;
+    string cur;
+    string::const_iterator i = s.begin();
+    while (i != s.end()) {
+        if (*i == '.') {
+            res.push_back(cur);
+            cur.clear();
+        } else if (*i == '"') {
+            ++i;
+            while (1) {
+                if (i == s.end())
+                    throw Error(format("missing closing quote in selection path `%1%'") % s);
+                if (*i == '"') break;
+                cur.push_back(*i++);
+            }
+        } else
+            cur.push_back(*i);
+        ++i;
+    }
+    if (!cur.empty()) res.push_back(cur);
+    return res;
+}
+
+
 Value * findAlongAttrPath(EvalState & state, const string & attrPath,
     Bindings & autoArgs, Value & vIn)
 {
-    Strings tokens = tokenizeString<Strings>(attrPath, ".");
+    Strings tokens = parseAttrPath(attrPath);
 
     Error attrError =
         Error(format("attribute selection path `%1%' does not match expression") % attrPath);
 
-    string curPath;
-
     Value * v = &vIn;
 
     foreach (Strings::iterator, i, tokens) {
 
-        if (!curPath.empty()) curPath += ".";
-        curPath += *i;
-
         /* Is *i an index (integer) or a normal attribute name? */
         enum { apAttr, apIndex } apType = apAttr;
         string attr = *i;
@@ -43,11 +64,14 @@ Value * findAlongAttrPath(EvalState & state, const string & attrPath,
             if (v->type != tAttrs)
                 throw TypeError(
                     format("the expression selected by the selection path `%1%' should be a set but is %2%")
-                    % curPath % showType(*v));
+                    % attrPath % showType(*v));
+
+            if (attr.empty())
+                throw Error(format("empty attribute name in selection path `%1%'") % attrPath);
 
             Bindings::iterator a = v->attrs->find(state.symbols.create(attr));
             if (a == v->attrs->end())
-                throw Error(format("attribute `%1%' in selection path `%2%' not found") % attr % curPath);
+                throw Error(format("attribute `%1%' in selection path `%2%' not found") % attr % attrPath);
             v = &*a->value;
         }
 
@@ -56,10 +80,10 @@ Value * findAlongAttrPath(EvalState & state, const string & attrPath,
             if (v->type != tList)
                 throw TypeError(
                     format("the expression selected by the selection path `%1%' should be a list but is %2%")
-                    % curPath % showType(*v));
+                    % attrPath % showType(*v));
 
             if (attrIndex >= v->list.length)
-                throw Error(format("list index %1% in selection path `%2%' is out of range") % attrIndex % curPath);
+                throw Error(format("list index %1% in selection path `%2%' is out of range") % attrIndex % attrPath);
 
             v = v->list.elems[attrIndex];
         }