Improve rendering performance

Avoid unnecessary copies via Utils.extend in hot paths.

lib/handlebars/helpers.js

@@ -20,7 +20,8 @@ export function moveHelperToHooks(instance, helperName, keepHelper) {
   if (instance.helpers[helperName]) {
     instance.hooks[helperName] = instance.helpers[helperName];
     if (!keepHelper) {
-      delete instance.helpers[helperName];
+      // Using delete is slow
+      instance.helpers[helperName] = undefined;
     }
   }
 }

lib/handlebars/internal/create-new-lookup-object.js

@@ -1,11 +0,0 @@
-import { extend } from '../utils';
-
-/**
- * Create a new object with "null"-prototype to avoid truthy results on prototype properties.
- * The resulting object can be used with "object[property]" to check if a property exists
- * @param {...object} sources a varargs parameter of source objects that will be merged
- * @returns {object}
- */
-export function createNewLookupObject(...sources) {
-  return extend(Object.create(null), ...sources);
-}

lib/handlebars/internal/proto-access.js

@@ -1,32 +1,30 @@
-import { createNewLookupObject } from './create-new-lookup-object';
+import { extend } from '../utils';
 import logger from '../logger';
 
 const loggedProperties = Object.create(null);
 
 export function createProtoAccessControl(runtimeOptions) {
-  let defaultMethodWhiteList = Object.create(null);
-  defaultMethodWhiteList['constructor'] = false;
-  defaultMethodWhiteList['__defineGetter__'] = false;
-  defaultMethodWhiteList['__defineSetter__'] = false;
-  defaultMethodWhiteList['__lookupGetter__'] = false;
-
-  let defaultPropertyWhiteList = Object.create(null);
+  // Create an object with "null"-prototype to avoid truthy results on
+  // prototype properties.
+  const propertyWhiteList = Object.create(null);
   // eslint-disable-next-line no-proto
-  defaultPropertyWhiteList['__proto__'] = false;
+  propertyWhiteList['__proto__'] = false;
+  extend(propertyWhiteList, runtimeOptions.allowedProtoProperties);
+
+  const methodWhiteList = Object.create(null);
+  methodWhiteList['constructor'] = false;
+  methodWhiteList['__defineGetter__'] = false;
+  methodWhiteList['__defineSetter__'] = false;
+  methodWhiteList['__lookupGetter__'] = false;
+  extend(methodWhiteList, runtimeOptions.allowedProtoMethods);
 
   return {
     properties: {
-      whitelist: createNewLookupObject(
-        defaultPropertyWhiteList,
-        runtimeOptions.allowedProtoProperties
-      ),
+      whitelist: propertyWhiteList,
       defaultValue: runtimeOptions.allowProtoPropertiesByDefault,
     },
     methods: {
-      whitelist: createNewLookupObject(
-        defaultMethodWhiteList,
-        runtimeOptions.allowedProtoMethods
-      ),
+      whitelist: methodWhiteList,
       defaultValue: runtimeOptions.allowProtoMethodsByDefault,
     },
   };

lib/handlebars/runtime.js

@@ -71,17 +71,10 @@ export function template(templateSpec, env) {
     }
     partial = env.VM.resolvePartial.call(this, partial, context, options);
 
-    let extendedOptions = Utils.extend({}, options, {
-      hooks: this.hooks,
-      protoAccessControl: this.protoAccessControl,
-    });
+    options.hooks = this.hooks;
+    options.protoAccessControl = this.protoAccessControl;
 
-    let result = env.VM.invokePartial.call(
-      this,
-      partial,
-      context,
-      extendedOptions
-    );
+    let result = env.VM.invokePartial.call(this, partial, context, options);
 
     if (result == null && env.compile) {
       options.partials[options.name] = env.compile(
@@ -89,7 +82,7 @@ export function template(templateSpec, env) {
         templateSpec.compilerOptions,
         env
       );
-      result = options.partials[options.name](context, extendedOptions);
+      result = options.partials[options.name](context, options);
     }
     if (result != null) {
       if (options.indent) {
@@ -255,8 +248,9 @@ export function template(templateSpec, env) {
 
   function _setup(options) {
     if (!options.partial) {
-      let mergedHelpers = Utils.extend({}, env.helpers, options.helpers);
-      wrapHelpersToPassLookupProperty(mergedHelpers, container);
+      let mergedHelpers = {};
+      addHelpers(mergedHelpers, env.helpers, container);
+      addHelpers(mergedHelpers, options.helpers, container);
       container.helpers = mergedHelpers;
 
       if (templateSpec.usePartial) {
@@ -417,9 +411,10 @@ function executeDecorators(fn, prog, container, depths, data, blockParams) {
   return prog;
 }
 
-function wrapHelpersToPassLookupProperty(mergedHelpers, container) {
-  Object.keys(mergedHelpers).forEach((helperName) => {
-    let helper = mergedHelpers[helperName];
+function addHelpers(mergedHelpers, helpers, container) {
+  if (!helpers) return;
+  Object.keys(helpers).forEach((helperName) => {
+    let helper = helpers[helperName];
     mergedHelpers[helperName] = passLookupPropertyOption(helper, container);
   });
 }
@@ -427,6 +422,7 @@ function wrapHelpersToPassLookupProperty(mergedHelpers, container) {
 function passLookupPropertyOption(helper, container) {
   const lookupProperty = container.lookupProperty;
   return wrapHelper(helper, (options) => {
-    return Utils.extend({ lookupProperty }, options);
+    options.lookupProperty = lookupProperty;
+    return options;
   });
 }