feature: plugin API, working on #86

README.md

@@ -230,6 +230,25 @@ engine.registerTag('upper', {
 
 See existing tag implementations here: <https://github.com/harttle/liquidjs/blob/master/tags/>
 
+## Plugin API
+
+A pack of tags or filters can be encapsulated into a **plugin**, which will be typically installed via npm.
+
+```javascript
+engine.plugin(require('./some-plugin'));
+
+// some-plugin.js
+module.exports = function (Liquid) {
+    // here `this` refers to the engine instance
+    // `Liquid` provides facilities to implement tags and filters
+    this.registerFilter('foo', x => x);
+}
+```
+
+Plugin List:
+
+* To add your plugin, contact me or simply send a PR.
+
 [nunjucks]: http://mozilla.github.io/nunjucks/
 [liquid-node]: https://github.com/sirlantis/liquid-node
 [shopify/liquid]: https://shopify.github.io/liquid/

src/index.js

@@ -75,6 +75,9 @@ const _engine = {
   registerTag: function (name, tag) {
     return this.tag.register(name, tag)
   },
+  plugin: function (plugin) {
+    return plugin.call(this, Liquid)
+  },
   express: function (opts) {
     opts = opts || {}
     const self = this

test/unit/index.js

@@ -12,6 +12,24 @@ describe('Liquid', function () {
       }).to.throw(/illegal root/)
     })
   })
+  describe('#plugin()', function () {
+    it('should call plugin on the instance', async function () {
+      const engine = new Liquid()
+      engine.plugin(function (Liquid) {
+        this.registerFilter('foo', x => `foo${x}foo`)
+      })
+      const html = await engine.parseAndRender('{{"bar"|foo}}')
+      expect(html).to.equal('foobarfoo')
+    })
+    it('should call plugin with Liquid', async function () {
+      const engine = new Liquid()
+      engine.plugin(function (Liquid) {
+        this.registerFilter('t', x => Liquid.isFalsy(x))
+      })
+      const html = await engine.parseAndRender('{{false|t}}')
+      expect(html).to.equal('true')
+    })
+  })
   describe('#express()', function () {
     const liquid = new Liquid({root: '/root'})
     const render = liquid.express()