support await after / await use (#92)

* support await of use as alternative to after * fix version check * only queue after in in microtask when asyncQ has items * ci trigger * __proto__ -> Object.create, reuse then func * expound upon await use usage via comparison with after example * await use comprehensive test * assimilate * await after * rm unused param * assimilate -> _loadRegistered * ci trigger * node 6 test compat * rm version check in tests * add failing test for after grouping * set then directly on instance for chaining compatiblity * autoStart: false support * Avoid chainable await as it breaks override * rm stray todo, dry code (thenify) Co-authored-by: Matteo Collina <[email protected]>
fastify · Feb 12, 2020 · 04b95b9 · 04b95b9
1 parent 2c89091
commit 04b95b9
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diff --git a/README.md b/README.md
@@ -76,6 +76,7 @@ async function third (instance, opts) {
   * <a href="#constructor"><code><b>avvio()</b></code></a>
   * <a href="#use"><code>instance.<b>use()</b></code></a>
   * <a href="#after"><code>instance.<b>after()</b></code></a>
+  * <a href="#await-after"><code>await instance.<b>after()</b></code></a>
   * <a href="#ready"><code>instance.<b>ready()</b></code></a>
   * <a href="#start"><code>instance.<b>start()</b></code></a>
   * <a href="#override"><code>instance.<b>override()</b></code></a>
@@ -144,7 +145,7 @@ app.on('start', () => {
 -------------------------------------------------------
 <a name="use"></a>
 
-### app.use(func, [optsOrFunc])
+### app.use(func, [optsOrFunc]) => Thenable
 
 Loads one or more functions asynchronously.
 
@@ -163,17 +164,62 @@ app.use(plugin)
 `done` should be called only once, when your plugin is ready to go.  Additional
 calls to `done` are ignored.
 
-async/await is also supported:
+`use` returns a thenable wrapped instance on which `use` is called, to support a chainable API that can also be awaited.
+
+This way, async/await is also supported and `use` can be awaited instead of using `after`.
+
+Example using `after`:
 
 ```js
-async function plugin (server, opts) {
-  await sleep(10)
+async function main () {
+  console.log('begin')
+  app.use(async function (server, opts) {
+    await sleep(10)
+    console.log('this first')
+  })
+  app.after(async (err) => {
+    if (err) throw err
+    console.log('then this')
+  })
+  await app.ready()
+  console.log('ready')
 }
+main().catch((err) => console.error(err))
+```
 
-app.use(plugin)
+Example using `await after`:
+
+
+```js
+async function main () {
+  console.log('begin')
+  app.use(async function (server, opts) {
+    await sleep(10)
+    console.log('this first')
+  })
+  await app.after()
+  console.log('then this')
+  await app.ready()
+  console.log('ready')
+}
+main().catch((err) => console.error(err))
 ```
 
-`use` returns the instance on which `use` is called, to support a chainable API.
+Example using `await use`:
+
+```js
+async function main () {
+  console.log('begin')
+  await app.use(async function (server, opts) {
+    await sleep(10)
+    console.log('this first')
+  })
+  console.log('then this')
+  await app.ready()
+  console.log('ready')
+}
+main().catch((err) => console.error(err))
+```
 
 A function that returns the options argument instead of an object is supported as well:
 
@@ -242,6 +288,8 @@ in [`ready`](#ready).
 Calls a function after all the previously defined plugins are loaded, including
 all their dependencies. The `'start'` event is not emitted yet.
 
+Note: `await after` can be used as an awaitable alternative to `after(func)`, or `await use` can be also as a shorthand for `use(plugin); await after()`.
+
 The callback changes basing on the parameters your are giving:
 1. If no parameter is given to the callback and there is an error, that error will be passed to the next error handler.
 2. If one parameter is given to the callback, that parameter will be the `error` object.
@@ -290,7 +338,39 @@ app.after(async function () {
 
 `done` must be called only once.
 
-Returns the instance on which `after` is called, to support a chainable API.
+If called with a function, it returns the instance on which `after` is called, to support a chainable API.
+
+-------------------------------------------------------
+<a name="await-after"></a>
+
+### await app.after() | app.after() => Promise
+
+Calling after with no function argument loads any plugins previously registered via `use` and returns a promise which resolves when all plugins registered so far have loaded.
+
+```js
+async function main () {
+  app.use(async function (server, opts) {
+    await sleep(10)
+    console.log('this first')
+  })
+  app.use(async function (server, opts) {
+    await sleep(10)
+    console.log('this second')
+  })
+  console.log('before after')
+  await app.after()
+  console.log('after after')
+  app.use(async function (server, opts) {
+    await sleep(10)
+    console.log('this third')
+  })
+  await app.ready()
+  console.log('ready')
+}
+main().catch((err) => console.error(err))
+```
+
+Unlike `after` and `use`, `await after` is *not* chainable.
 
 -------------------------------------------------------
 <a name="ready"></a>

diff --git a/boot.js b/boot.js
@@ -27,14 +27,16 @@ function wrap (server, opts, instance) {
     throw new Error(readyKey + '() is already defined, specify an expose option')
   }
 
-  server[useKey] = function (a, b, c) {
-    instance.use(a, b, c)
-    return this
+  server[useKey] = function (fn, opts) {
+    instance.use(fn, opts)
+    return instance
   }
 
+  Object.defineProperty(server, 'then', { get: thenify.bind(instance) })
+
   server[afterKey] = function (func) {
     if (typeof func !== 'function') {
-      throw new Error('not a function')
+      return instance._loadRegistered()
     }
     instance.after(encapsulateThreeParam(func, this))
     return this
@@ -105,6 +107,7 @@ function Boot (server, opts, done) {
   this._current = []
   this._error = null
   this._isOnCloseHandlerKey = Symbol('isOnCloseHandler')
+  this._lastUsed = null
 
   this.setMaxListeners(0)
 
@@ -133,18 +136,18 @@ function Boot (server, opts, done) {
   }
 
   this._doStart = null
-  const main = new Plugin(this, root.bind(this), opts, noop, 0)
-
-  main.once('start', (serverName, funcName, time) => {
+  this._root = new Plugin(this, root.bind(this), opts, noop, 0)
+  this._root.once('start', (serverName, funcName, time) => {
     const nodeId = this.pluginTree.start(null, funcName, time)
-    main.once('loaded', (serverName, funcName, time) => {
+    this._root.once('loaded', (serverName, funcName, time) => {
       this.pluginTree.stop(nodeId, time)
     })
   })
 
-  Plugin.loadPlugin.call(this, main, (err) => {
+  Plugin.loadPlugin.call(this, this._root, (err) => {
     debug('root plugin ready')
     this.emit('preReady')
+    this._root = null
     if (err) {
       this._error = err
       if (this._readyQ.length() === 0) {
@@ -187,11 +190,31 @@ function assertPlugin (plugin) {
 
 // load a plugin
 Boot.prototype.use = function (plugin, opts) {
-  this._addPlugin(plugin, opts, false)
-
+  this._lastUsed = this._addPlugin(plugin, opts, false)
   return this
 }
 
+Boot.prototype._loadRegistered = function (plugin) {
+  plugin = plugin || this._lastUsed
+  return new Promise((resolve) => {
+    if (plugin && !plugin.loaded) {
+      plugin.asyncQ.push(() => {
+        resolve()
+      })
+    } else {
+      resolve()
+    }
+
+    // if the root plugin is not loaded, let's resume that
+    // so one can use after() befor calling ready
+    if (!this.started && !this.booted) {
+      this._root.q.resume()
+    }
+  })
+}
+
+Object.defineProperty(Boot.prototype, 'then', { get: thenify })
+
 Boot.prototype._addPlugin = function (plugin, opts, isAfter) {
   assertPlugin(plugin)
   opts = opts || {}
@@ -221,6 +244,8 @@ Boot.prototype._addPlugin = function (plugin, opts, isAfter) {
       this._error = err
     }
   })
+
+  return obj
 }
 
 Boot.prototype.after = function (func) {
@@ -313,6 +338,17 @@ Boot.prototype.toJSON = function () {
 
 function noop () { }
 
+function thenify () {
+  // If the instance is ready, then there is
+  // nothing to await. This is true during
+  // await server.ready() as ready() resolves
+  // with the server, end we will end up here
+  // because of automatic promise chaining.
+  if (this.booted) return
+  const p = this._loadRegistered()
+  return p.then.bind(p)
+}
+
 function callWithCbOrNextTick (func, cb, context) {
   context = this._server
   var err = this._error

diff --git a/package.json b/package.json
@@ -43,6 +43,7 @@
   "dependencies": {
     "archy": "^1.0.0",
     "debug": "^4.0.0",
-    "fastq": "^1.6.0"
+    "fastq": "^1.6.0",
+    "queue-microtask": "^1.1.2"
   }
 }
diff --git a/plugin.js b/plugin.js
@@ -1,5 +1,5 @@
 'use strict'
-
+const queueMicrotask = require('queue-microtask')
 const fastq = require('fastq')
 const EE = require('events').EventEmitter
 const inherits = require('util').inherits
@@ -36,9 +36,13 @@ function Plugin (parent, func, optsOrFunc, isAfter, timeout) {
   this.timeout = timeout === undefined ? parent._timeout : timeout
   this.name = getName(func)
   this.isAfter = isAfter
-
   this.q = fastq(parent, loadPlugin, 1)
   this.q.pause()
+  this.asyncQ = fastq(parent, (resolve, cb) => {
+    resolve(this.server)
+    cb()
+  }, 1)
+  this.asyncQ.pause()
   this.loaded = false
 
   // always start the queue in the next tick
@@ -73,6 +77,31 @@ Plugin.prototype.exec = function (server, cb) {
 
   var timer
 
+  const done = (err) => {
+    if (completed) {
+      debug('loading complete', name)
+      return
+    }
+
+    if (err) {
+      debug('exec errored', name)
+
+      // In case of errors, we need to kickstart
+      // the asyncQ as it won't get started otherwise
+      this.asyncQ.resume()
+    } else {
+      debug('exec completed', name)
+    }
+
+    completed = true
+
+    if (timer) {
+      clearTimeout(timer)
+    }
+
+    cb(err)
+  }
+
   if (this.timeout > 0) {
     debug('setting up timeout', name, this.timeout)
     timer = setTimeout(function () {
@@ -87,33 +116,22 @@ Plugin.prototype.exec = function (server, cb) {
 
   this.emit('start', this.server ? this.server.name : null, this.name, Date.now())
   var promise = func(this.server, this.opts, done)
+
   if (promise && typeof promise.then === 'function') {
     debug('resolving promise', name)
+    queueMicrotask(() => {
+      if (this.asyncQ.length() > 0) {
+        this.server.after(() => {
+          this.asyncQ.resume()
+        })
+      }
+      this.q.resume()
+    })
+
     promise.then(
       () => process.nextTick(done),
       (e) => process.nextTick(done, e))
   }
-
-  function done (err) {
-    if (completed) {
-      debug('loading complete', name)
-      return
-    }
-
-    if (err) {
-      debug('exec errored', name)
-    } else {
-      debug('exec completed', name)
-    }
-
-    completed = true
-
-    if (timer) {
-      clearTimeout(timer)
-    }
-
-    cb(err)
-  }
 }
 
 Plugin.prototype.enqueue = function (obj, cb) {
@@ -144,7 +162,16 @@ Plugin.prototype.finish = function (err, cb) {
   const check = () => {
     debug('check', this.name, this.q.length(), this.q.running())
     if (this.q.length() === 0 && this.q.running() === 0) {
-      done()
+      if (this.asyncQ.length() > 0) {
+        this.asyncQ.drain = () => {
+          this.asyncQ.drain = noop
+          this.asyncQ.pause()
+          check()
+        }
+        this.asyncQ.resume()
+      } else {
+        done()
+      }
     } else {
       debug('delayed', this.name)
       // finish when the queue of nested plugins to load is empty