Bluebird - 承诺是在处理程序中创建的，但未从中返回 [英] Bluebird — a promise was created in a handler but was not returned from it

问题描述

首先，我知道我必须返回承诺以避免此警告。我也尝试按照建议的方式返回 null 在这里的文档。考虑一下这段代码，我在Mongoose的预保存挂钩中使用它，但我在其他地方遇到过这个警告：

First of all, I know that I have to return promises to avoid this warning. I've also tried returning null as suggested here in the docs. Consider this piece of code, I'm using it in Mongoose's pre-save hook, but I've experienced this warning in other places:

var Story = mongoose.model('Story', StorySchema);

StorySchema.pre('save', function(next) {
    var story = this;

    // Fetch all stories before save to automatically assign
    // some variable, avoiding conflict with other stories
    return Story.find().then(function(stories) {

        // Some code, then set story.somevar value
        story.somevar = somevar;
        return null;
    }).then(next).catch(next); // <-- this line throws warning
});

我也尝试过（最初）这种方式：

I've also tried (initially) this way:

        story.somevar = somevar;
        return next(); // <-- this line throws warning
    }).catch(next);

但它也不起作用。哦，我必须提一下，我使用Bluebird：

But it doesn't work either. Oh, and I have to mention, that I use Bluebird:

var Promise = require('bluebird'),
    mongoose = require('mongoose');

mongoose.Promise = Promise;

不是一个承诺是在一个处理程序中创建的但是没有从它返回，那个人忘了回来一个承诺。

Not a duplicate of A promise was created in a handler but was not returned from it, the guy forgot to return a promise.

推荐答案

问题几乎是使用 next 回调所有，它调用创建promises而不返回它们的函数。理想情况下，钩子只需要返回承诺而不是回调。

The problem is pretty much using a next callback at all, which calls functions that create promises without returning them. Ideally the hooks just needed to return promises instead of taking callbacks.

您应该能够通过使用

.then(function(result) {
    next(null, result);
    return null;
}, function(error) {
    next(error);
    return null;
});

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