Rework lookup null protector logic

- Move the lookup null protection out of `nameLookup` and into that contexts that are aware of the needs for falsy vs. not displayed values.
- Optimize lookup for nested path operations

Fixes #731

1 files changed, 5 insertions, 10 deletions

diff --git a/lib/handlebars/compiler/compiler.js b/lib/handlebars/compiler/compiler.js
index e5f2280..31176c9 100644
--- a/lib/handlebars/compiler/compiler.js
+++ b/lib/handlebars/compiler/compiler.js
@@ -275,6 +275,8 @@ Compiler.prototype = {
     } else if (this.options.knownHelpersOnly) {
       throw new Exception("You specified knownHelpersOnly, but used the unknown helper " + name, sexpr);
     } else {
+      id.falsy = true;
+
       this.ID(id);
       this.opcode('invokeHelper', params.length, id.original, sexpr.isRoot);
     }
@@ -298,23 +300,16 @@ Compiler.prototype = {
 
     var name = id.parts[0];
     if (!name) {
+      // Context reference, i.e. `{{foo .}}` or `{{foo ..}}`
       this.opcode('pushContext');
     } else {
-      this.opcode('lookupOnContext', id.parts[0]);
-    }
-
-    for(var i=1, l=id.parts.length; i<l; i++) {
-      this.opcode('lookup', id.parts[i]);
+      this.opcode('lookupOnContext', id.parts, id.falsy);
     }
   },
 
   DATA: function(data) {
     this.options.data = true;
-    this.opcode('lookupData', data.id.depth);
-    var parts = data.id.parts;
-    for(var i=0, l=parts.length; i<l; i++) {
-      this.opcode('lookup', parts[i]);
-    }
+    this.opcode('lookupData', data.id.depth, data.id.parts);
   },
 
   STRING: function(string) {