✨New {{concat}} helper

- allows for concatenating strings using helpers and variables like {{concat (url) "?query=" slug}}

core/frontend/helpers/concat.js

@@ -0,0 +1,8 @@
+const {SafeString} = require('./proxy');
+
+module.exports = function concat(...args) {
+    const options = args.pop();
+    const separator = options.hash.separator || '';
+
+    return new SafeString(args.join(separator));
+};

core/frontend/helpers/index.js

@@ -8,6 +8,7 @@ coreHelpers.asset = require('./asset');
 coreHelpers.author = require('./author');
 coreHelpers.authors = require('./authors');
 coreHelpers.body_class = require('./body_class');
+coreHelpers.concat = require('./concat');
 coreHelpers.content = require('./content');
 coreHelpers.date = require('./date');
 coreHelpers.encode = require('./encode');
@@ -43,6 +44,7 @@ registerAllCoreHelpers = function registerAllCoreHelpers() {
     registerThemeHelper('author', coreHelpers.author);
     registerThemeHelper('authors', coreHelpers.authors);
     registerThemeHelper('body_class', coreHelpers.body_class);
+    registerThemeHelper('concat', coreHelpers.concat);
     registerThemeHelper('content', coreHelpers.content);
     registerThemeHelper('date', coreHelpers.date);
     registerThemeHelper('encode', coreHelpers.encode);

core/test/unit/helpers/concat_spec.js

@@ -0,0 +1,98 @@
+const should = require('should');
+const helpers = require.main.require('core/frontend/helpers');
+const handlebars = require.main.require('core/frontend/services/themes/engine').handlebars;
+
+const configUtils = require('../../utils/configUtils');
+
+let defaultGlobals;
+
+function compile(templateString) {
+    const template = handlebars.compile(templateString);
+    template.with = (locals = {}, globals) => {
+        globals = globals || defaultGlobals;
+
+        return template(locals, globals);
+    };
+
+    return template;
+}
+
+describe('{{concat}} helper', function () {
+    before(function () {
+        handlebars.registerHelper('concat', helpers.concat);
+        handlebars.registerHelper('url', helpers.url);
+        configUtils.config.set('url', 'https://siteurl.com');
+
+        defaultGlobals = {
+            data: {
+                site: {
+                    url: configUtils.config.get('url')
+                }
+            }
+        };
+    });
+
+    it('can correctly concat nothing', function () {
+        compile('{{concat}}')
+            .with({})
+            .should.eql('');
+    });
+
+    it('can correctly concat things that resolve to empty', function () {
+        compile('{{concat tag.slug slug}}')
+        .with({tag: {}})
+        .should.eql('');
+    });
+
+    it('can concat simple strings', function () {
+        compile('{{concat "hello" "world"}}')
+            .with({})
+            .should.eql('helloworld');
+    });
+
+    it('can concat simple strings with a custom separator', function () {
+        compile('{{concat "hello" "world" separator=" "}}')
+            .with({})
+            .should.eql('hello world');
+    });
+
+    it('can concat strings and numbers', function () {
+        compile('{{concat "abcd" 1234}}')
+            .with({})
+            .should.eql('abcd1234');
+    });
+
+    it('can concat strings and global variables', function () {
+        compile('{{concat @site.url "?my=param"}}')
+            .with({})
+            .should.eql('https://siteurl.com?my=param');
+    });
+
+    it('can concat strings and local variables', function () {
+        compile('{{concat tag.slug "?my=param"}}')
+            .with({tag: {slug: 'my-tag'}})
+            .should.eql('my-tag?my=param');
+    });
+
+    it('can concat strings from custom helpers (SafeStrings)', function () {
+        compile('{{concat (url) "?my=param"}}')
+            // Simulate a post - using a draft to prove url helper gets called
+            // because published posts get their urls from a cache that we don't have access to, so we just get 404
+            .with({title: 'My Draft Post', slug: 'my-post', html: '<p>My Post</p>', uuid: '1234'})
+            .should.eql('/p/1234/?my=param');
+    });
+
+    it('can concat mixed args', function () {
+        compile('{{concat @site.url (url) "?slug=" slug}}')
+            // Simulate a post - using a draft to prove url helper gets called
+            // because published posts get their urls from a cache that we don't have access to, so we just get 404
+            .with({title: 'My Draft Post', slug: 'my-post', html: '<p>My Post</p>', uuid: '1234'})
+            .should.eql('https://siteurl.com/p/1234/?slug=my-post');
+    });
+
+    it('will output object Object for sill args', function () {
+        compile('{{concat @site "?my=param"}}')
+            .with({})
+            .should.eql('[object Object]?my=param');
+    });
+});

core/test/unit/helpers/index_spec.js

@@ -8,7 +8,7 @@ var should = require('should'),
 describe('Helpers', function () {
     var hbsHelpers = ['each', 'if', 'unless', 'with', 'helperMissing', 'blockHelperMissing', 'log', 'lookup', 'block', 'contentFor'],
         ghostHelpers = [
-            'asset', 'author', 'authors', 'body_class', 'content', 'date', 'encode', 'excerpt', 'facebook_url', 'foreach', 'get',
+            'asset', 'author', 'authors', 'body_class', 'concat', 'content', 'date', 'encode', 'excerpt', 'facebook_url', 'foreach', 'get',
             'ghost_foot', 'ghost_head', 'has', 'img_url', 'is', 'lang', 'meta_description', 'meta_title', 'navigation',
             'next_post', 'page_url', 'pagination', 'plural', 'post_class', 'prev_post', 'reading_time', 't', 'tags', 'title', 'twitter_url',
             'url'