pn

The pn library gives you the Promise-using node standard library
you've always dreamed of. Think "Promised Node" when saying it.

Just about every node standard library method that takes a callback will now
return a Promise iff no callback is supplied. But existing code
that passes callbacks will still work fine --- and fast: No unnecessary
Promises are created if you supply a callback.

The wrappers are generated automatically by a script, with a table to
handle exceptions and odd cases. See below for more details.

Installation

npm install pn

Usage

var fs = require('pn/fs');
fs.writeFile('foo', 'bar', 'utf-8').then(function() { console.log('done'); });
// But you can use callbacks, too -- existing code won't break.
fs.writeFile('foo', 'bat', 'utf-8', function(err) { console.log('yay'); });

This library uses node native promises (ie global.Promise) by
default, and thus works with node >= 0.11.

You can use core-js or
es6-shim
to add ES6 Promises to earlier versions of node, for example:
require('es6-shim'); var fs = require('pn/fs');
Just be sure that es6-shim is loaded before the pn package in that
case.

You might also want to look into packages like
prfun
which add some helpers to make working with native promises much more
fun.

In particular, the Promise#done method is very useful when
debugging, at least until v8's native Promise debugging
capabilities are completed.

Custom Promise types

You can also specify a custom Promise type to use, as follows:
var MyPromise = require('prfun'); // Use prfun's Promises, for example. require('pn/_promise')(MyPromise); // This only needs to be done once.

Exceptions and odd cases

The wrappers are automatically generated by scripts/generate.js;
there is a table in that file which specifies all the odd cases.

In general: if the node API has a callback which takes multiple
value arguments, the Promise returned will be an object with
named fields corresponding to the different values. If the node
API takes a callback and returns a value, pn will return
the original value with a nonenumerable field named promise
corresponding to the callback. Combining these two cases:
var child_process = require('pn/child_process'); var cp = child_process.execFile('true'); console.log('pid', cp.pid); cp.promise.then(function(result) { console.log('stdout: ', result.stdout); console.log('stderr: ', result.stderr); });

• child_process: The exec and execFile methods promise a object
  with fields named stdout and stderr. They return a ChildProcess
  object with a nonenumerable field named promise corresponding to the
  callback.
• crypto: The randomBytes and pseudoRandomBytes methods are
  now always asynchronous, returning a Promise if no callback
  is supplied. Use the new randomBytesSync and pseudoRandomBytesSync
  methods if you want synchronous computation. This is backwards
  incompatible with existing node code.
• dns: The lookupService method promises an object with
  fields named hostname and service.
• fs: The exists method doesn't pass an error to its callback.
  The promisied version will never reject. The write method promises
  an object with fields named written and data. The read method
  promises an object with fields named read and data.
• http, https: The request and get methods return a ClientRequest
  object with a nonenumerable field named promise, which will
  resolve to an IncomingMessage object.
• process: You can defer computation to the next tick with
  require('pn/process').nextTick().then(function(){...})
• tls: The connect and createServer return objects with a
  nonenumerable field named promise.

There are a few object methods which are not promisified by this
package:
* domain: Domain#bind, Domain#intercept
* http,https: ClientRequest#setTimeout, IncomingMessage#setTimeout,
Server#setTimeout, ServerResponse#setTimeout, Server#listen,
Server#close
* net: Server#listen, Server#close, Server#getConnections,
Socket#write, Socket#setTimeout
* readline: Interface#question
* stream: Writable#write, Writable#end
* dgram: Socket#send, Socket#bind.

Related packages

Here are some other packages with similar aims:
* promised-node
* then-fs
* final-fs

License

Copyright (c) 2014-2018 C. Scott Ananian

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.