slice theme helper

ghost/core/core/frontend/helpers/slice.js

@@ -0,0 +1,30 @@
+// # slice helper
+//
+// Usage examples, for example in .hbs theme templates:
+//
+// {{#match (slice label start=0 end=2) "@ " }}
+//   <li><a href="{{url}}">{{ slice label start=2 }}</a</li>
+// {{/match}}
+//
+// Or:
+//
+// {{ slice "Testing [*]" start=-3 }} => Outputs: [*]
+
+const {SafeString} = require('../services/handlebars');
+
+module.exports = function slice(text, options) {
+    options = options || {};
+    options.hash = options.hash || {};
+
+    let start = options.hash.start;
+    let end = options.hash.end;
+
+    if (typeof text !== 'string' || typeof start !== 'number') {
+        return '';
+    }
+
+    let result = (typeof end === 'number') ?
+        text.slice(start, end) : text.slice(start);
+
+    return new SafeString(result);
+};

ghost/core/test/unit/frontend/helpers/slice.test.js

@@ -0,0 +1,90 @@
+const should = require('should');
+const handlebars = require('../../../../core/frontend/services/theme-engine/engine').handlebars;
+
+const slice = require('../../../../core/frontend/helpers/slice');
+const match = require('../../../../core/frontend/helpers/match');
+
+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('{{slice}} helper', function () {
+    before(function () {
+        handlebars.registerHelper('slice', slice);
+        handlebars.registerHelper('match', match);
+        configUtils.config.set('url', 'https://siteurl.com');
+
+        defaultGlobals = {
+            data: {
+                site: {
+                    url: configUtils.config.get('url')
+                }
+            }
+        };
+    });
+
+    it('can correctly slice nothing', function () {
+        compile('{{slice}}')
+            .with({})
+            .should.eql('');
+    });
+
+    it('can correctly slice things that resolve to empty', function () {
+        compile('{{slice tag.slug start=2}}')
+            .with({tag: {}})
+            .should.eql('');
+    });
+
+    it('can slice simple strings', function () {
+        compile('{{slice "@ Mail" start=2}}')
+            .with({})
+            .should.eql('Mail');
+    });
+
+    it('can slice simple strings with end', function () {
+        compile('{{slice "@ Mail" start=0 end=2}}')
+            .with({})
+            .should.eql('@ ');
+    });
+
+    it('can slice simple strings with end', function () {
+        compile('{{slice @site.url start=0 end=5}}')
+            .with({})
+            .should.eql('https');
+    });
+
+    it('can silently return empty string with non integer start', function () {
+        compile('{{slice "- Test" start="12"}}')
+            .with({})
+            .should.eql('');
+    });
+
+    it('can ignore non integer end', function () {
+        compile('{{slice "- Test" start=2 end="end"}}')
+            .with({})
+            .should.eql('Test');
+    });
+
+    it('can work with minus start value', function () {
+        compile('{{slice "Test ->" start=-2}}')
+            .with({})
+            .should.eql('->');
+    });
+
+    it('can be used as sub expression', function () {
+        compile('{{#match (slice "- Test" start=0 end=2) "- "}}true{{else}}false{{/match}}')
+            .with({})
+            .should.eql('true');
+    });
+});

ghost/core/test/unit/frontend/services/theme-engine/handlebars/helpers.test.js

@@ -10,7 +10,8 @@ describe('Helpers', function () {
     const ghostHelpers = [
         'asset', 'authors', 'body_class', 'cancel_link', 'concat', 'content', 'content_api_key', 'content_api_url', 'date', 'encode', 'excerpt', 'facebook_url', 'foreach', 'get',
         'ghost_foot', 'ghost_head', 'has', 'img_url', 'is', 'link', 'link_class', 'meta_description', 'meta_title', 'navigation',
-        'next_post', 'page_url', 'pagination', 'plural', 'post_class', 'prev_post', 'price', 'raw', 'reading_time', 't', 'tags', 'title','total_members', 'total_paid_members', 'twitter_url',
+        'next_post', 'page_url', 'pagination', 'plural', 'post_class', 'prev_post', 'price', 'raw', 'reading_time', 'slice', 't',
+        'tags', 'title','total_members', 'total_paid_members', 'twitter_url',
         'url', 'comment_count', 'collection', 'recommendations', 'readable_url'
     ];
     const experimentalHelpers = ['match', 'tiers', 'comments', 'search'];