HTML helpers refactor - issue TryGhost#246 items 2 and 5.

- moved template logic out of individual helpers and into Ghost
- simplified template-driven helpers into closures which maintain the context of handlebars
- with handlebars context we have access to data, so don't need to pass data in
- check data to test that it is a simple object and not a function
- moved helpers back into index.js
- provided tests for both template functions in ghost and the nav helper so we are back to where we were

core/frontend/helpers/index.js

@@ -1,12 +1,14 @@
 var _ = require('underscore'),
     moment = require('moment'),
     when = require('when'),
-    pagination = require('./paginate'),
-    navHelper = require('./navigation'),
     hbs = require('express-hbs'),
+    errors = require('../../shared/errorHandling'),
     coreHelpers;
 
 coreHelpers = function (ghost) {
+    var navHelper,
+        paginationHelper;
+
     /**
      * [ description]
      * @todo ghost core helpers + a way for themes to register them
@@ -119,10 +121,40 @@ coreHelpers = function (ghost) {
         }
         return ret;
     });
-    // Just one async helper for now, but could be more in the future
+
+    // ## Template driven helpers
+    // Template driven helpers require that their template is loaded before they can be registered.
+
+    // ###Nav Helper
+    // `{{nav}}`
+    // Outputs a navigation menu built from items in config.js
+    navHelper = ghost.loadTemplate('nav').then(function (templateFn) {
+        ghost.registerThemeHelper('nav', function (options) {
+            if (!_.isObject(this.navItems) || _.isFunction(this.navItems)) {
+                errors.logAndThrowError('navItems data is not an object or is a function');
+                return;
+            }
+            return new hbs.handlebars.SafeString(templateFn({links: this.navItems}));
+        });
+    });
+
+    // ### Pagination Helper
+    // `{{paginate}}`
+    // Outputs previous and next buttons, along with info about the current page
+    paginationHelper = ghost.loadTemplate('pagination').then(function (templateFn) {
+        ghost.registerThemeHelper('paginate', function (options) {
+            if (!_.isObject(this.pagination) || _.isFunction(this.pagination)) {
+                errors.logAndThrowError('pagination data is not an object or is a function');
+                return;
+            }
+            return new hbs.handlebars.SafeString(templateFn(this.pagination));
+        });
+    });
+
+    // Return once the template-driven helpers have loaded
     return when.join(
-        navHelper.registerWithGhost(ghost),
-        pagination.registerWithGhost(ghost)
+        navHelper,
+        paginationHelper
     );
 };
 

core/ghost.js

@@ -6,8 +6,10 @@ var config = require('./../config'),
     when = require('when'),
     express = require('express'),
     errors = require('../core/shared/errorHandling'),
+    fs = require('fs'),
     path = require('path'),
     hbs = require('express-hbs'),
+    nodefn = require('when/node/function'),
     _ = require('underscore'),
     Polyglot = require('node-polyglot'),
 
@@ -167,6 +169,21 @@ Ghost.prototype.updateSettingsCache = function (settings) {
     }
 };
 
+// ## Template utils
+
+Ghost.prototype.compileTemplate = function (templatePath) {
+    return nodefn.call(fs.readFile, templatePath).then(function (templateContents) {
+        return hbs.handlebars.compile(templateContents.toString());
+    }, errors.logAndThrowError);
+};
+
+Ghost.prototype.loadTemplate = function (name) {
+    // TODO: allow themes to override these templates
+    var templatePath = path.join(this.paths().frontendViews, name + '.hbs');
+
+    return this.compileTemplate(templatePath);
+};
+
 /**
  * @param  {string}   name
  * @param  {Function} fn

core/test/ghost/fixtures/test.hbs

@@ -0,0 +1 @@
+<h1>HelloWorld</h1>

core/test/ghost/frontend_helpers_index_spec.js

@@ -0,0 +1,55 @@
+/*globals describe, beforeEach, it*/
+var should = require('should'),
+    sinon = require('sinon'),
+    when = require('when'),
+    _ = require('underscore'),
+    handlebars = require('express-hbs').handlebars,
+    path = require('path'),
+    helpers = require('../../frontend/helpers'),
+    Ghost = require('../../ghost');
+
+describe('Core Helpers', function () {
+
+    var ghost;
+
+    beforeEach(function () {
+        ghost = new Ghost();
+    });
+
+
+    describe('Navigation Helper', function () {
+
+        it('can render nav items', function (done) {
+            var templateSpy = sinon.spy(function (data) { return "rendered " + data.links.length; }),
+                compileSpy = sinon.stub(ghost, 'compileTemplate').returns(when.resolve(templateSpy)),
+                fakeNavItems = [{
+                    title: 'test1',
+                    url: '/test1'
+                }, {
+                    title: 'test2',
+                    url: '/test2'
+                }],
+                rendered;
+
+            helpers.loadCoreHelpers(ghost).then(function () {
+
+                should.exist(handlebars.helpers.nav);
+
+                rendered = handlebars.helpers.nav.call({navItems: fakeNavItems});
+
+                // Returns a string returned from navTemplateFunc
+                should.exist(rendered);
+                rendered.string.should.equal("rendered 2");
+
+                compileSpy.called.should.equal(true);
+                templateSpy.called.should.equal(true);
+                templateSpy.calledWith({ links: fakeNavItems }).should.equal(true);
+
+
+                compileSpy.restore();
+
+                done();
+            }, done);
+        });
+    });
+});