Pass an already imported module in helper

README.md

@@ -349,11 +349,12 @@ There are two utilities provided:
 - `build`: builds your application and returns the `fastify` instance without calling the `listen` method.
 - `listen`: starts your application and returns the `fastify` instance listening on the configured port.
 
-Both of these utilities have the `function(args, pluginOptions, serverOptions)` parameters:
+Both of these utilities have the `function(args, pluginOptions, serverOptions, serverModule)` parameters:
 
 - `args`: is a string or a string array within the same arguments passed to the `fastify-cli` command.
 - `pluginOptions`: is an object containing the options provided to the started plugin (eg: `app.js`).
 - `serverOptions`: is an object containing the additional options provided to fastify server, similar to the `--options` command line argument
+- `serverModule`: is an optional parameter used to provide the already imported main server plugin module, instead of letting the helper import it.
 
 ```js
 // load the utility helper functions

helper.d.ts

@@ -1,8 +1,9 @@
 import fastify from 'fastify'
 
 declare module 'fastify-cli/helper.js' {
-  module helper {
-    export function build (args: Array<string>, additionalOptions?: Object, serverOptions?: Object): ReturnType<typeof fastify>
+  namespace helper {
+    export function build (args: Array<string>, additionalOptions?: Object, serverOptions?: Object, serverModule?: Object): ReturnType<typeof fastify>
+    export function listen (args: Array<string>, additionalOptions?: Object, serverOptions?: Object, serverModule?: Object): ReturnType<typeof fastify>
   }
 
   export = helper

helper.js

@@ -3,14 +3,14 @@
 const { runFastify } = require('./start')
 
 module.exports = {
-  build (args, additionalOptions = {}, serverOptions = {}) {
+  build (args, additionalOptions = {}, serverOptions = {}, serverModule = undefined) {
     Object.defineProperty(additionalOptions, 'ready', {
       value: true,
       enumerable: false,
       writable: false
     })
 
-    return runFastify(args, additionalOptions, serverOptions)
+    return runFastify(args, additionalOptions, serverOptions, serverModule)
   },
   listen: runFastify
 }

start.js

@@ -96,7 +96,7 @@ async function preloadESModules (opts) {
   })
 }
 
-async function runFastify (args, additionalOptions, serverOptions) {
+async function runFastify (args, additionalOptions, serverOptions, serverModule) {
   const opts = parseArgs(args)
 
   if (opts.require) {
@@ -113,7 +113,7 @@ async function runFastify (args, additionalOptions, serverOptions) {
   let file = null
 
   try {
-    file = await requireServerPluginFromPath(opts._[0])
+    file = serverModule ?? await requireServerPluginFromPath(opts._[0])
   } catch (e) {
     return module.exports.stop(e)
   }

test/helper.test.js

@@ -161,3 +161,10 @@ test('should ensure can access all decorators', async t => {
   t.teardown(() => app2.close())
   t.ok(app2.test)
 })
+
+test('should return the fastify instance when using serverModule', async t => {
+  const argv = ['']
+  const app = await helper.build(argv, {}, {}, require('../examples/plugin.js'))
+  t.teardown(() => app.close())
+  t.notOk(app.server.listening)
+})