refactor(themes): extract the {{relative}} helper to be standalone + add some tests

src/website/theme.js

@@ -81,11 +81,6 @@ class Theme {
       const fullPath = path.join(this.dir, 'helpers', filename)
       handlebars.registerHelper(name, require(fullPath))
     })
-
-    // render a relative path
-    handlebars.registerHelper('relative', (target, options) => {
-      return path.relative(path.dirname(options.data.root.album.path), target)
-    })
   }
 
   renderStyles (done) {

test/themes/helpers/relative.spec.js

@@ -0,0 +1,27 @@
+const date = require('../../../themes/base/helpers/relative')
+const handlebars = require('handlebars')
+const should = require('should/as-function')
+
+describe('Handlebars helpers: relative', () => {
+  handlebars.registerHelper('relative', date)
+
+  it('returns a path in the same folder', () => {
+    const template = handlebars.compile(`<link rel="stylesheet" href="{{relative 'public/theme.css'}}" />`)
+    const res = template({
+      album: {
+        path: 'index.html'
+      }
+    })
+    should(res).eql('<link rel="stylesheet" href="public/theme.css" />')
+  })
+
+  it('returns a relative path for albums in nested folders', () => {
+    const template = handlebars.compile(`<link rel="stylesheet" href="{{relative 'public/theme.css'}}" />`)
+    const res = template({
+      album: {
+        path: 'albums/holidays.html'
+      }
+    })
+    should(res).eql('<link rel="stylesheet" href="../public/theme.css" />')
+  })
+})

themes/base/helpers/relative.js

@@ -0,0 +1,6 @@
+const path = require('path')
+
+module.exports = (target, options) => {
+  const albumPath = options.data.root.album.path
+  return path.relative(path.dirname(albumPath), target)
+}