add isPromiseLike (#222)

Author: Uzlopak

boot.js

@@ -20,6 +20,7 @@ const { debug } = require('./lib/debug')
 const { validatePlugin } = require('./lib/validate-plugin')
 const { isBundledOrTypescriptPlugin } = require('./lib/is-bundled-or-typescript-plugin')
 const { loadPlugin } = require('./lib/load-plugin')
+const { isPromiseLike } = require('./lib/is-promise-like')
 
 function wrap (server, opts, instance) {
   const expose = opts.expose || {}
@@ -408,14 +409,14 @@ function callWithCbOrNextTick (func, cb) {
   if (func.length === 0) {
     this._error = err
     res = func()
-    if (res && !res[kAvvio] && typeof res.then === 'function') {
+    if (isPromiseLike(res) && !res[kAvvio]) {
       res.then(() => process.nextTick(cb), (e) => process.nextTick(cb, e))
     } else {
       process.nextTick(cb)
     }
   } else if (func.length === 1) {
     res = func(err)
-    if (res && !res[kAvvio] && typeof res.then === 'function') {
+    if (isPromiseLike(res) && !res[kAvvio]) {
       res.then(() => process.nextTick(cb), (e) => process.nextTick(cb, e))
     } else {
       process.nextTick(cb)

lib/is-promise-like.js

@@ -0,0 +1,17 @@
+'use strict'
+
+/**
+ * @param {any} maybePromiseLike
+ * @returns {maybePromiseLike is PromiseLike}
+ */
+function isPromiseLike (maybePromiseLike) {
+  return (
+    maybePromiseLike !== null &&
+    typeof maybePromiseLike === 'object' &&
+    typeof maybePromiseLike.then === 'function'
+  )
+}
+
+module.exports = {
+  isPromiseLike
+}

lib/load-plugin.js

@@ -1,5 +1,7 @@
 'use strict'
 
+const { isPromiseLike } = require('./is-promise-like')
+
 /**
  * @callback LoadPluginCallback
  * @param {Error} [err]
@@ -13,7 +15,7 @@
  * @param {LoadPluginCallback} callback
  */
 function loadPlugin (instance, plugin, callback) {
-  if (typeof plugin.func.then === 'function') {
+  if (isPromiseLike(plugin.func)) {
     plugin.func.then((fn) => {
       if (typeof fn.default === 'function') {
         fn = fn.default

plugin.js

@@ -8,6 +8,7 @@ const { loadPlugin } = require('./lib/load-plugin')
 const { createPromise } = require('./lib/create-promise')
 const { AVV_ERR_READY_TIMEOUT } = require('./lib/errors')
 const { getPluginName } = require('./lib/get-plugin-name')
+const { isPromiseLike } = require('./lib/is-promise-like')
 
 function Plugin (parent, func, options, isAfter, timeout) {
   this.started = false
@@ -99,7 +100,7 @@ Plugin.prototype.exec = function (server, cb) {
   this.emit('start', this.server ? this.server.name : null, this.name, Date.now())
   const promise = func(this.server, this.opts, done)
 
-  if (promise && typeof promise.then === 'function') {
+  if (isPromiseLike(promise)) {
     debug('exec: resolving promise', name)
 
     promise.then(

test/lib/is-promise-like.test.js

@@ -0,0 +1,20 @@
+'use strict'
+
+const { test } = require('tap')
+const { isPromiseLike } = require('../../lib/is-promise-like')
+
+test('isPromiseLike', (t) => {
+  t.plan(9)
+
+  t.equal(isPromiseLike(1), false)
+  t.equal(isPromiseLike('function'), false)
+  t.equal(isPromiseLike({}), false)
+  t.equal(isPromiseLike([]), false)
+  t.equal(isPromiseLike(null), false)
+
+  t.equal(isPromiseLike(function () {}), false)
+  t.equal(isPromiseLike(new Promise((resolve) => resolve)), true)
+  t.equal(isPromiseLike(Promise.resolve()), true)
+
+  t.equal(isPromiseLike({ then: () => {} }), true)
+})