Add support for returned, rejected Promises to router.param

closes #91
closes #92

HISTORY.md

@@ -3,6 +3,8 @@
 
 This incorporates all changes after 1.3.5 up to 1.3.6.
 
+ * Add support for returned, rejected Promises to `router.param`
+
 2.0.0-beta.1 / 2020-03-29
 =========================
 

README.md

@@ -115,6 +115,11 @@ Maps the specified path parameter `name` to a specialized param-capturing middle
 
 This function positions the middleware in the same stack as `.use`.
 
+The function can optionally return a `Promise` object. If a `Promise` object
+is returned from the function, the router will attach an `onRejected` callback
+using `.then`. If the promise is rejected, `next` will be called with the
+rejected value, or an error if the value is falsy.
+
 Parameter mapping is used to provide pre-conditions to routes
 which use normalized placeholders. For example a _:user_id_ parameter
 could automatically load a user's information from the database without

index.js

@@ -13,6 +13,7 @@
  */
 
 var flatten = require('array-flatten').flatten
+var isPromise = require('is-promise')
 var Layer = require('./lib/layer')
 var methods = require('methods')
 var mixin = require('utils-merge')
@@ -642,7 +643,12 @@ function processParams (params, layer, called, req, res, done) {
  if (!fn) return param()
 
  try {
- fn(req, res, paramCallback, paramVal, key.name)
+ var ret = fn(req, res, paramCallback, paramVal, key.name)
+ if (isPromise(ret)) {
+ ret.then(null, function (error) {
+ paramCallback(error || new Error('Rejected promise'))
+ })
+ }
  } catch (e) {
  paramCallback(e)
  }

lib/layer.js

@@ -12,6 +12,7 @@
  * @private
  */
 
+var isPromise = require('is-promise')
 var pathRegexp = require('path-to-regexp')
 
 /**
@@ -187,20 +188,6 @@ function decodeParam (val) {
  }
 }
 
-/**
- * Returns true if the val is a Promise.
- *
- * @param {*} val
- * @return {boolean}
- * @private
- */
-
-function isPromise (val) {
- return val &&
- typeof val === 'object' &&
- typeof val.then === 'function'
-}
-
 /**
  * Loosens the given path for path-to-regexp matching.
  */

package.json

@@ -10,6 +10,7 @@
  "repository": "pillarjs/router",
  "dependencies": {
  "array-flatten": "3.0.0",
+ "is-promise": "4.0.0",
  "methods": "~1.1.2",
  "parseurl": "~1.3.3",
  "path-to-regexp": "3.2.0",

test/param.js

@@ -10,6 +10,8 @@ var shouldNotHitHandle = utils.shouldNotHitHandle
 var createServer = utils.createServer
 var request = utils.request
 
+var describePromises = global.Promise ? describe : describe.skip
+
 describe('Router', function () {
  describe('.param(name, fn)', function () {
  it('should reject missing name', function () {
@@ -254,6 +256,48 @@ describe('Router', function () {
  .expect(500, /Error: boom/, done)
  })
 
+ describePromises('promise support', function () {
+ it('should pass rejected promise value', function (done) {
+ var router = new Router()
+ var server = createServer(router)
+
+ router.param('user', function parseUser (req, res, next, user) {
+ return Promise.reject(new Error('boom'))
+ })
+
+ router.get('/user/:user', function (req, res) {
+ res.setHeader('Content-Type', 'text/plain')
+ res.end('get user ' + req.params.id)
+ })
+
+ request(server)
+ .get('/user/bob')
+ .expect(500, /Error: boom/, done)
+ })
+
+ it('should pass rejected promise without value', function (done) {
+ var router = new Router()
+ var server = createServer(router)
+
+ router.use(function createError (req, res, next) {
+ return Promise.reject() // eslint-disable-line prefer-promise-reject-errors
+ })
+
+ router.param('user', function parseUser (req, res, next, user) {
+ return Promise.reject() // eslint-disable-line prefer-promise-reject-errors
+ })
+
+ router.get('/user/:user', function (req, res) {
+ res.setHeader('Content-Type', 'text/plain')
+ res.end('get user ' + req.params.id)
+ })
+
+ request(server)
+ .get('/user/bob')
+ .expect(500, /Error: Rejected promise/, done)
+ })
+ })
+
  describe('next("route")', function () {
  it('should cause route with param to be skipped', function (done) {
  var cb = after(3, done)