improve DecoratorHandler

lib/handler/decorator-handler.js

@@ -1,35 +1,44 @@
 'use strict'
 
 module.exports = class DecoratorHandler {
+  #handler
+
   constructor (handler) {
-    this.handler = handler
+    if (typeof handler !== 'object' || handler === null) {
+      throw new TypeError('handler must be an object')
+    }
+    this.#handler = handler
   }
 
   onConnect (...args) {
-    return this.handler.onConnect(...args)
+    return this.#handler.onConnect(...args)
   }
 
   onError (...args) {
-    return this.handler.onError(...args)
+    return this.#handler.onError(...args)
   }
 
   onUpgrade (...args) {
-    return this.handler.onUpgrade(...args)
+    return this.#handler.onUpgrade(...args)
+  }
+
+  onResponseStarted (...args) {
+    return this.#handler.onResponseStarted?.(...args)
   }
 
   onHeaders (...args) {
-    return this.handler.onHeaders(...args)
+    return this.#handler.onHeaders(...args)
   }
 
   onData (...args) {
-    return this.handler.onData(...args)
+    return this.#handler.onData(...args)
   }
 
   onComplete (...args) {
-    return this.handler.onComplete(...args)
+    return this.#handler.onComplete(...args)
   }
 
   onBodySent (...args) {
-    return this.handler.onBodySent(...args)
+    return this.#handler.onBodySent(...args)
   }
 }

test/decorator-handler.js

@@ -0,0 +1,68 @@
+'use strict'
+
+const { tspl } = require('@matteo.collina/tspl')
+const { describe, test } = require('node:test')
+const DecoratorHandler = require('../lib/handler/decorator-handler')
+
+const methods = [
+  'onConnect',
+  'onError',
+  'onUpgrade',
+  'onHeaders',
+  'onResponseStarted',
+  'onData',
+  'onComplete',
+  'onBodySent'
+]
+
+describe('DecoratorHandler', () => {
+  test('should throw if provided handler is not an object', (t) => {
+    t = tspl(t, { plan: 4 })
+    t.throws(() => new DecoratorHandler(null), new TypeError('handler must be an object'))
+    t.throws(() => new DecoratorHandler('string'), new TypeError('handler must be an object'))
+
+    t.throws(() => new DecoratorHandler(null), new TypeError('handler must be an object'))
+    t.throws(() => new DecoratorHandler('string'), new TypeError('handler must be an object'))
+  })
+
+  test('should not expose the handler', (t) => {
+    t = tspl(t, { plan: 1 })
+    const handler = {}
+    const decorator = new DecoratorHandler(handler)
+    t.strictEqual(Object.keys(decorator).length, 0)
+  })
+
+  methods.forEach((method) => {
+    test(`should have delegate ${method} method`, (t) => {
+      t = tspl(t, { plan: 1 })
+      const decorator = new DecoratorHandler({})
+      t.equal(typeof decorator[method], 'function')
+    })
+
+    test(`should delegate ${method}`, (t) => {
+      t = tspl(t, { plan: 1 })
+      const handler = { [method]: () => method }
+      const decorator = new DecoratorHandler(handler)
+      t.equal(decorator[method](), method)
+    })
+
+    test(`should delegate ${method} with arguments`, (t) => {
+      t = tspl(t, { plan: 1 })
+      const handler = { [method]: (...args) => args }
+      const decorator = new DecoratorHandler(handler)
+      t.deepStrictEqual(decorator[method](1, 2, 3), [1, 2, 3])
+    })
+
+    test(`can be extended and should delegate ${method}`, (t) => {
+      t = tspl(t, { plan: 1 })
+
+      class ExtendedHandler extends DecoratorHandler {
+        [method] () {
+          return method
+        }
+      }
+      const decorator = new ExtendedHandler({})
+      t.equal(decorator[method](), method)
+    })
+  })
+})