Implement recursive field lookup in compat mode

Provides the mustache behavior of recursive lookup without the use of depthed paths.

Note that this does incur a fairly dramatic performance penalty for depthed queries.

bench/throughput.js

@@ -28,11 +28,13 @@ function makeSuite(bench, name, template, handlebarsOnly) {
       partials = template.partials,
 
       handlebarsOut,
+      compatOut,
       dustOut,
       ecoOut,
       mustacheOut;
 
   var handlebar = Handlebars.compile(template.handlebars, {data: false}),
+      compat =  Handlebars.compile(template.handlebars, {data: false, compat: true}),
       options = {helpers: template.helpers};
   _.each(template.partials && template.partials.handlebars, function(partial, name) {
     Handlebars.registerPartial(name, Handlebars.compile(partial, {data: false}));
@@ -43,6 +45,11 @@ function makeSuite(bench, name, template, handlebarsOnly) {
     handlebar(context, options);
   });
 
+  compatOut = compat(context, options);
+  bench("compat", function() {
+    compat(context, options);
+  });
+
   if (handlebarsOnly) {
     return;
   }
@@ -107,6 +114,7 @@ function makeSuite(bench, name, template, handlebarsOnly) {
     }
   }
 
+  compare(compatOut, 'compat');
   compare(dustOut, 'dust');
   compare(ecoOut, 'eco');
   compare(mustacheOut, 'mustache');

lib/handlebars/compiler/compiler.js

@@ -308,7 +308,7 @@ Compiler.prototype = {
       // Context reference, i.e. `{{foo .}}` or `{{foo ..}}`
       this.opcode('pushContext');
     } else {
-      this.opcode('lookupOnContext', id.parts, id.falsy);
+      this.opcode('lookupOnContext', id.parts, id.falsy, id.isScoped);
     }
   },
 
@@ -424,6 +424,9 @@ export function precompile(input, options, env) {
   if (!('data' in options)) {
     options.data = true;
   }
+  if (options.compat) {
+    options.useDepths = true;
+  }
 
   var ast = env.parse(input);
   var environment = new env.Compiler().compile(ast, options);
@@ -440,6 +443,9 @@ export function compile(input, options, env) {
   if (!('data' in options)) {
     options.data = true;
   }
+  if (options.compat) {
+    options.useDepths = true;
+  }
 
   var compiled;
 

lib/handlebars/compiler/javascript-compiler.js

@@ -17,6 +17,11 @@ JavaScriptCompiler.prototype = {
       return parent + "['" + name + "']";
     }
   },
+  depthedLookup: function(name) {
+    this.aliases.lookup = 'this.lookup';
+
+    return 'lookup(depths, "' + name + '")';
+  },
 
   compilerInfo: function() {
     var revision = COMPILER_REVISION,
@@ -69,7 +74,7 @@ JavaScriptCompiler.prototype = {
 
     this.compileChildren(environment, options);
 
-    this.useDepths = this.useDepths || environment.depths.list.length;
+    this.useDepths = this.useDepths || environment.depths.list.length || this.options.compat;
 
     var opcodes = environment.opcodes,
         opcode,
@@ -356,15 +361,20 @@ JavaScriptCompiler.prototype = {
   //
   // Looks up the value of `name` on the current context and pushes
   // it onto the stack.
-  lookupOnContext: function(parts, falsy) {
+  lookupOnContext: function(parts, falsy, scoped) {
     /*jshint -W083 */
-    this.pushContext();
-    if (!parts) {
-      return;
+    var i = 0,
+        len = parts.length;
+
+    if (!scoped && this.isChild && this.options.compat && !this.lastContext) {
+      // The depthed query is expected to handle the undefined logic for the root level that
+      // is implemented below, so we evaluate that directly in compat mode
+      this.pushStackLiteral(this.depthedLookup(parts[i++]));
+    } else {
+      this.pushContext();
     }
 
-    var len = parts.length;
-    for (var i = 0; i < len; i++) {
+    for (; i < len; i++) {
       this.replaceStack(function(current) {
         var lookup = this.nameLookup(current, parts[i], 'context');
         // We want to ensure that zero and false are handled properly for the first element

lib/handlebars/runtime.js

@@ -63,6 +63,14 @@ export function template(templateSpec, env) {
 
   // Just add water
   var container = {
+    lookup: function(depths, name) {
+      var len = depths.length;
+      for (var i = 0; i < len; i++) {
+        if (depths[i] && depths[i][name] != null) {
+          return depths[i][name];
+        }
+      }
+    },
     lambda: function(current, context) {
       return typeof current === 'function' ? current.call(context) : current;
     },

spec/blocks.js

@@ -94,4 +94,25 @@ describe('blocks', function() {
         'No people\n');
     });
   });
+
+  describe('compat mode', function() {
+    it("block with deep recursive lookup lookup", function() {
+      var string = "{{#outer}}Goodbye {{#inner}}cruel {{omg}}{{/inner}}{{/outer}}";
+      var hash = {omg: "OMG!", outer: [{ inner: [{ text: "goodbye" }] }] };
+
+      shouldCompileTo(string, [hash, undefined, undefined, true], "Goodbye cruel OMG!");
+    });
+    it("block with deep recursive pathed lookup", function() {
+      var string = "{{#outer}}Goodbye {{#inner}}cruel {{omg.yes}}{{/inner}}{{/outer}}";
+      var hash = {omg: {yes: "OMG!"}, outer: [{ inner: [{ yes: 'no', text: "goodbye" }] }] };
+
+      shouldCompileTo(string, [hash, undefined, undefined, true], "Goodbye cruel OMG!");
+    });
+    it("block with missed recursive lookup", function() {
+      var string = "{{#outer}}Goodbye {{#inner}}cruel {{omg.yes}}{{/inner}}{{/outer}}";
+      var hash = {omg: {no: "OMG!"}, outer: [{ inner: [{ yes: 'no', text: "goodbye" }] }] };
+
+      shouldCompileTo(string, [hash, undefined, undefined, true], "Goodbye cruel ");
+    });
+  });
 });

spec/env/common.js

@@ -17,7 +17,7 @@ global.compileWithPartials = function(string, hashOrArray, partials) {
   if(Object.prototype.toString.call(hashOrArray) === "[object Array]") {
     ary = [];
     ary.push(hashOrArray[0]);
-    ary.push({ helpers: hashOrArray[1], partials: hashOrArray[2], compat: hashOrArray[3] });
+    ary.push({ helpers: hashOrArray[1], partials: hashOrArray[2] });
     options = {compat: hashOrArray[3]};
   } else {
     ary = [hashOrArray];