Add support for depthed resolution of data fields

lib/handlebars/base.js

@@ -223,5 +223,7 @@ export var logger = {
 export function log(level, obj) { logger.log(level, obj); }
 
 export var createFrame = function(object) {
-  return Utils.extend({}, object);
+  var frame = Utils.extend({}, object);
+  frame._parent = object;
+  return frame;
 };

lib/handlebars/compiler/compiler.js

@@ -310,11 +310,7 @@ Compiler.prototype = {
 
   DATA: function(data) {
     this.options.data = true;
-    if (data.id.isScoped || data.id.depth) {
+    this.opcode('lookupData', data.id.depth);
-      throw new Exception('Scoped data references are not supported: ' + data.original, data);
-    }
-
-    this.opcode('lookupData');
     var parts = data.id.parts;
     for(var i=0, l=parts.length; i<l; i++) {
       this.opcode('lookup', parts[i]);

lib/handlebars/compiler/javascript-compiler.js

@@ -403,8 +403,12 @@ JavaScriptCompiler.prototype = {
   // On stack, after: data, ...
   //
   // Push the data lookup operator
-  lookupData: function() {
+  lookupData: function(depth) {
-    this.pushStackLiteral('data');
+    if (!depth) {
+      this.pushStackLiteral('data');
+    } else {
+      this.pushStackLiteral('this.data(data, ' + depth + ')');
+    }
   },
 
   // [pushStringParam]

lib/handlebars/runtime.js

@@ -77,6 +77,12 @@ export function template(templateSpec, env) {
       }
       return data;
     },
+    data: function(data, depth) {
+      while (data && depth--) {
+        data = data._parent;
+      }
+      return data;
+    },
     merge: function(param, common) {
       var ret = param || common;
 

spec/data.js

@@ -85,22 +85,6 @@ describe('data', function() {
     equals("Hello undefined", result, "@foo as a parameter retrieves template data");
   });
 
-  it("parameter data throws when using this scope references", function() {
-    var string = "{{#goodbyes}}{{text}} cruel {{@./name}}! {{/goodbyes}}";
-
-    shouldThrow(function() {
-      CompilerContext.compile(string);
-    }, Error);
-  });
-
-  it("parameter data throws when using parent scope references", function() {
-    var string = "{{#goodbyes}}{{text}} cruel {{@../name}}! {{/goodbyes}}";
-
-    shouldThrow(function() {
-      CompilerContext.compile(string);
-    }, Error);
-  });
-
   it("parameter data throws when using complex scope references", function() {
     var string = "{{#goodbyes}}{{text}} cruel {{@foo/../name}}! {{/goodbyes}}";
 
@@ -251,4 +235,23 @@ describe('data', function() {
       equals('hello', result);
     });
   });
+
+  describe('nesting', function() {
+    it('the root context can be looked up via @root', function() {
+      var template = CompilerContext.compile('{{#helper}}{{#helper}}{{@./depth}} {{@../depth}} {{@../../depth}}{{/helper}}{{/helper}}');
+      var result = template({foo: 'hello'}, {
+        helpers: {
+          helper: function(options) {
+            var frame = Handlebars.createFrame(options.data);
+            frame.depth = options.data.depth + 1;
+            return options.fn(this, {data: frame});
+          }
+        },
+        data: {
+          depth: 0
+        }
+      });
+      equals('2 1 0', result);
+    });
+  });
 });

spec/parser.js

@@ -21,6 +21,10 @@ describe('parser', function() {
     equals(ast_for("{{@foo}}"), "{{ @ID:foo [] }}\n");
   });
 
+  it('parses simple mustaches with data paths', function() {
+    equals(ast_for("{{@../foo}}"), "{{ @ID:foo [] }}\n");
+  });
+
   it('parses mustaches with paths', function() {
     equals(ast_for("{{foo/bar}}"), "{{ PATH:foo/bar [] }}\n");
   });