feat: add support for dnsPrefetch

adonis-typings/index.ts

@@ -42,4 +42,10 @@ declare module '@ioc:Adonis/Addons/Shield' {
   export type IENoOpenOptions = {
     enabled: boolean,
   }
+
+  // X-DNS-Prefetch-Control
+  export type DnsPrefetchOptions = {
+    enabled: boolean,
+    allow?: boolean,
+  }
 }

src/dnsPrefetch.ts

@@ -0,0 +1,30 @@
+/*
+ * @adonisjs/shield
+ *
+ * (c) Harminder Virk <virk@adonisjs.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+*/
+
+/// <reference path="../adonis-typings/index.ts" />
+
+import { DnsPrefetchOptions } from '@ioc:Adonis/Addons/Shield'
+import { HttpContextContract } from '@ioc:Adonis/Core/HttpContext'
+import { noop } from './noop'
+
+/**
+ * Adds `X-Content-Type-Options` header based upon given
+ * user options
+ */
+export function dnsPrefetch (options: DnsPrefetchOptions) {
+  if (!options.enabled) {
+    return noop
+  }
+
+  const value = options.allow ? 'on' : 'off'
+
+  return function dnsPrefetchMiddlewareFn ({ response }: HttpContextContract) {
+    response.header('X-DNS-Prefetch-Control', value)
+  }
+}

test/dns-prefetch.spec.ts

@@ -0,0 +1,38 @@
+/*
+ * @adonisjs/shield
+ *
+ * (c) Harminder Virk <virk@adonisjs.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+*/
+
+import test from 'japa'
+import { HttpContext } from '@adonisjs/http-server/build/standalone'
+import { dnsPrefetch } from '../src/dnsPrefetch'
+
+test.group('Dns Prefetch', () => {
+  test('return noop function when enabled is false', (assert) => {
+    const middlewareFn = dnsPrefetch({ enabled: false })
+    const ctx = HttpContext.create('/', {}, {}, {}, {})
+    middlewareFn(ctx)
+
+    assert.isUndefined(ctx.response.getHeader('X-DNS-Prefetch-Control'))
+  })
+
+  test('set X-DNS-Prefetch-Control header', (assert) => {
+    const middlewareFn = dnsPrefetch({ enabled: true, allow: true })
+    const ctx = HttpContext.create('/', {}, {}, {}, {})
+    middlewareFn(ctx)
+
+    assert.equal(ctx.response.getHeader('X-DNS-Prefetch-Control'), 'on')
+  })
+
+  test('set X-DNS-Prefetch-Control header to off', (assert) => {
+    const middlewareFn = dnsPrefetch({ enabled: true, allow: false })
+    const ctx = HttpContext.create('/', {}, {}, {}, {})
+    middlewareFn(ctx)
+
+    assert.equal(ctx.response.getHeader('X-DNS-Prefetch-Control'), 'off')
+  })
+})