Use depths array rather than passing array args

Approximately doubles the throughput performance of depthed templates and clears the way for doing recursive path lookups in pathed mode.

lib/handlebars/compiler/javascript-compiler.js

@@ -69,6 +69,8 @@ JavaScriptCompiler.prototype = {
 
     this.compileChildren(environment, options);
 
+    this.useDepths = this.useDepths || environment.depths.list.length;
+
     var opcodes = environment.opcodes,
         opcode,
         i,
@@ -115,6 +117,9 @@ JavaScriptCompiler.prototype = {
       if (this.options.data) {
         ret.useData = true;
       }
+      if (this.useDepths) {
+        ret.depths = true;
+      }
 
       if (!asObject) {
         ret.compiler = JSON.stringify(ret.compiler);
@@ -151,8 +156,8 @@ JavaScriptCompiler.prototype = {
 
     var params = ["depth0", "helpers", "partials", "data"];
 
-    for(var i=0, l=this.environment.depths.list.length; i<l; i++) {
-      params.push("depth" + this.environment.depths.list[i]);
+    if (this.useDepths) {
+      params.push('depths');
     }
 
     // Perform a second pass over the output to merge content when possible
@@ -668,6 +673,8 @@ JavaScriptCompiler.prototype = {
         child.name = 'program' + index;
         this.context.programs[index] = compiler.compile(child, options, this.context, !this.precompile);
         this.context.environments[index] = child;
+
+        this.useDepths = this.useDepths || compiler.useDepths;
       } else {
         child.index = index;
         child.name = 'program' + index;
@@ -689,17 +696,17 @@ JavaScriptCompiler.prototype = {
     }
 
     var child = this.environment.children[guid],
-        depths = child.depths.list, depth;
+        depths = child.depths.list,
+        useDepths = this.useDepths,
+        depth;
 
     var programParams = [child.index, 'data'];
 
-    for(var i=0, l = depths.length; i<l; i++) {
-      depth = depths[i];
-
-      programParams.push('depth' + (depth - 1));
+    if (useDepths) {
+      programParams.push('depths');
     }
 
-    return (depths.length === 0 ? 'this.program(' : 'this.programWithDepth(') + programParams.join(', ') + ')';
+    return 'this.program(' + programParams.join(', ') + ')';
   },
 
   useRegister: function(name) {
@@ -847,7 +854,11 @@ JavaScriptCompiler.prototype = {
   },
 
   contextName: function(context) {
-    return 'depth' + context;
+    if (this.useDepths && context) {
+      return 'depths[' + context + ']';
+    } else {
+      return 'depth' + context;
+    }
   },
 
   quotedString: function(str) {

lib/handlebars/runtime.js

@@ -75,17 +75,16 @@ export function template(templateSpec, env) {
     },
 
     programs: [],
-    program: function(i, data) {
+    program: function(i, data, depths) {
       var programWrapper = this.programs[i],
           fn = this.fn(i);
-      if(data) {
-        programWrapper = program(this, i, fn, data);
+      if (data || depths) {
+        programWrapper = program(this, i, fn, data, depths);
       } else if (!programWrapper) {
         programWrapper = this.programs[i] = program(this, i, fn);
       }
       return programWrapper;
     },
-    programWithDepth: env.VM.programWithDepth,
 
     data: function(data, depth) {
       while (data && depth--) {
@@ -117,7 +116,12 @@ export function template(templateSpec, env) {
     if (!options.partial && templateSpec.useData) {
       data = initData(context, data);
     }
-    return templateSpec.main.call(container, context, container.helpers, container.partials, data);
+    var depths;
+    if (templateSpec.depths) {
+      depths = [context];
+    }
+
+    return templateSpec.main.call(container, context, container.helpers, container.partials, data, depths);
   };
 
   ret._setup = function(options) {
@@ -134,35 +138,23 @@ export function template(templateSpec, env) {
   };
 
   ret._child = function(i) {
+    if (templateSpec.depth) {
+      throw new Exception('_child can not be used with depthed methods');
+    }
+
     return container.programWithDepth(i);
   };
   return ret;
 }
 
-export function programWithDepth(i, data /*, $depth */) {
-  /*jshint -W040 */
-  var args = Array.prototype.slice.call(arguments, 2),
-      container = this,
-      fn = container.fn(i);
-
+export function program(container, i, fn, data, depths) {
   var prog = function(context, options) {
     options = options || {};
 
-    return fn.apply(container, [context, container.helpers, container.partials, options.data || data].concat(args));
+    return fn.call(container, context, container.helpers, container.partials, options.data || data, [context].concat(depths));
   };
   prog.program = i;
-  prog.depth = args.length;
-  return prog;
-}
-
-export function program(container, i, fn, data) {
-  var prog = function(context, options) {
-    options = options || {};
-
-    return fn.call(container, context, container.helpers, container.partials, options.data || data);
-  };
-  prog.program = i;
-  prog.depth = 0;
+  prog.depth = depths ? depths.length : 0;
   return prog;
 }