如何使用Bluebird宣传Node的child_process.exec和child_process.execFile函数？ [英] How to promisify Node's child_process.exec and child_process.execFile functions with Bluebird?

问题描述

我正在使用Node.js下的Bluebird promise库，这太棒了！但我有一个问题：

I'm using the Bluebird promise library under Node.js, it's great! But I have a question:

如果你看一下Node的文档 child_process.exec 和 child_process.execFile ，你可以看到这两个函数都在返回一个ChildProcess对象。

If you take a look at the documentation of Node's child_process.exec and child_process.execFile you can see that both of these functions are returning a ChildProcess object.

那么推荐这种函数的方法是什么？

So what's the recommended way to promisify such functions?

请注意以下工作（我得到了一个Promise对象）：

Note that the following works (I get a Promise object):

var Promise = require('bluebird');
var execAsync = Promise.promisify(require('child_process').exec);
var execFileAsync = Promise.promisify(require('child_process').execFile);

但是如何才能访问原始Node.js函数的原始返回值？ （在这些情况下，我需要能够访问最初返回的ChildProcess对象。）

But how can one get access to the original return value of the original Node.js functions? (In these cases I would need to be able to access the originally returned ChildProcess objects.)

任何建议都将不胜感激！

Any suggestion would be appreciated!

编辑：

这是一个使用child_process.exec函数返回值的示例代码：

Here is an example code which is using the return value of the child_process.exec function:

var exec = require('child_process').exec;
var child = exec('node ./commands/server.js');
child.stdout.on('data', function(data) {
    console.log('stdout: ' + data);
});
child.stderr.on('data', function(data) {
    console.log('stderr: ' + data);
});
child.on('close', function(code) {
    console.log('closing code: ' + code);
});

但如果我要使用exec函数的promisified版本（上面的execAsync）那么返回值将是一个承诺，而不是一个ChildProcess对象。这是我正在谈论的真正问题。

But if I would use the promisified version of the exec function ( execAsync from above ) then the return value will be a promise, not a ChildProcess object. This is the real problem I am talking about.

推荐答案

听起来你想从电话中回复两件事：

It sounds like you'd like to return two things from the call:

• ChildProcess


• 在ChildProcess完成时解析的承诺

那么推荐的方式来宣传这些功能？ 不要。

So "the recommended way to promisify such functions"? Don't.

你不在大会之外。承诺返回函数有望返回一个承诺，就是这样。你可以返回一个有两个成员的对象（ChildProcess& promise），但这只会让人感到困惑。

You're outside the convention. Promise returning functions are expected to return a promise, and that's it. You could return an object with two members (the ChildProcess & the promise), but that'll just confuse people.

我建议调用unpromisified函数，并且根据返回的childProcess创建一个promise。 （也许将其包装成辅助函数）

I'd suggest calling the unpromisified function, and creating a promise based off the returned childProcess. (Maybe wrap that into a helper function)

这样，对于下一个读取代码的人来说，这是非常明确的。

This way, it's quite explicit for the next person who reads the code.

类似于：

var Promise = require('bluebird');
var exec = require('child_process').execFile;

function promiseFromChildProcess(child) {
    return new Promise(function (resolve, reject) {
        child.addListener("error", reject);
        child.addListener("exit", resolve);
    });
}

var child = exec('ls');

promiseFromChildProcess(child).then(function (result) {
    console.log('promise complete: ' + result);
}, function (err) {
    console.log('promise rejected: ' + err);
});

child.stdout.on('data', function (data) {
    console.log('stdout: ' + data);
});
child.stderr.on('data', function (data) {
    console.log('stderr: ' + data);
});
child.on('close', function (code) {
    console.log('closing code: ' + code);
});

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