Bluebird 被遗忘 return 警告丢失

Question

我希望 Bluebird forgotten return warning 出现，但由于某些原因它不起作用。

一个demo:

const Bluebird = require('bluebird');

Bluebird.config({
    warnings: true
})

Bluebird.resolve(1)
.then(() => {
    Bluebird.resolve(2); // should warn about forgotten return
})
.then(two => console.log(two));

如何解决输出警告？

我怀疑我以前遇到过这个问题，但我不记得解决方案是什么。

Answer 1

似乎需要启用长堆栈跟踪才能显示警告。您可以使用配置对象来启用它们 (docs) (demo):

Bluebird.config({
    warnings: true,
    longStackTraces: true
});

或环境变量（docs) (demo）：

In Node.js you may configure warnings and long stack traces for the entire process using environment variables:
BLUEBIRD_LONG_STACK_TRACES=1 BLUEBIRD_WARNINGS=1 node app.js
Both features are automatically enabled if the BLUEBIRD_DEBUG environment variable has been set or if the NODE_ENV environment variable is equal to "development".

和

To enable long stack traces and warnings in node development:
$ NODE_ENV=development node server.js
To enable long stack traces and warnings in node production:
$ BLUEBIRD_DEBUG=1 node server.js
See Environment Variables.

编辑为什么这是必要的：

似乎默认情况下禁用警告和长堆栈跟踪，并且仅在检测到开发环境时才启用，参见 here:

Note that even though false is the default here, a development environment might be detected which automatically enables long stack traces and warnings.

要在生产环境中显示警告，您不仅必须启用警告，还必须启用长堆栈跟踪，请参阅 here and here。

Answer 2

您可以使用配置对象中 wForgottenReturn 和 longStackTraces 属性的组合来配置检查遗忘 return 语句的警告。 wForgottenReturn 是 warning 的属性，必须设置为 true，并且是唯一可以单独配置的警告类型。对应的环境变量key为BLUEBIRD_W_FORGOTTEN_RETURN。您可以查看 documentation 了解更多信息。

const Bluebird = require('bluebird');

Bluebird.config({
    warnings: {
        wForgottenReturn: true
    }, longStackTraces: true,
});


Bluebird.resolve(1).then(() => {
   Bluebird.resolve(2);
}).then(two => console.log(two));

运行控制台中的程序给我：

Warning: a promise was created in a handler at /home/adrianpop/test/bb.js:11:13 but was not returned from it, see 
    at Function.Promise.cast (/home/adrianpop/Downloads/Test/node_modules/bluebird/js/release/promise.js:196:13)
undefined

这是你想要的输出。

您还可以运行申请为：

BLUEBIRD_LONG_STACK_TRACES=1 BLUEBIRD_WARNINGS=1 node app.js，产生相同的结果。

干杯！

编辑：

从 github 上的 this 问题，我们有：

So the problem is that by default Nodejs 6.x does not display stack traces for warnings. There is a command line option (--trace-warnings) to enable them. Without this option Bluebird warnings are a lot less useful. Without the call stack, it can be very difficult to figure out where the warning originated.

还可以找到更多信息：

Answer 3

一言以蔽之，

How can it be fixed to output a warning?

通过启用长堆栈跟踪。

const Bluebird = require('bluebird');

Bluebird.config({
    warnings: true,
    longStackTraces: true
})

Bluebird.resolve(1)
.then(() => {
    Bluebird.resolve(2); // should warn about forgotten return
})
.then(two => console.log(two));

现在应该让你得到一个 new demo，它会标记你这个错误：

(node:65) Warning: a promise was created in a handler at evalmachine.<anonymous>:16:14 but was not returned from it, see http://bluebirdjs.com/docs/warning-explanations.html#warning-a-promise-was-created-in-a-handler-but-was-not-returned-from-it
    at Function.Promise.cast (/home/runner/node_modules/bluebird/js/release/promise.js:196:13)
undefined

promise.js 文件:


Promise.cast = function (obj) {
    var ret = tryConvertToPromise(obj);
    if (!(ret instanceof Promise)) {
        ret = new Promise(INTERNAL);
        ret._captureStackTrace(); //promise.js:196:13 
        ret._setFulfilled();
        ret._rejectionHandler0 = obj;
    }
    return ret;
};

请记住，在 Node.js 中，您可以选择使用环境变量为整个过程配置警告和长堆栈跟踪。

进入 bluebird 的源代码


var warnings = !!(util.env("BLUEBIRD_WARNINGS") != 0 &&
    (debugging || util.env("BLUEBIRD_WARNINGS")));

var longStackTraces = !!(util.env("BLUEBIRD_LONG_STACK_TRACES") != 0 &&
    (debugging || util.env("BLUEBIRD_LONG_STACK_TRACES")));

var wForgottenReturn = util.env("BLUEBIRD_W_FORGOTTEN_RETURN") != 0 &&
    (warnings || !!util.env("BLUEBIRD_W_FORGOTTEN_RETURN"));

和

Promise.config = function(opts) {
    opts = Object(opts);
    if ("longStackTraces" in opts) {
        if (opts.longStackTraces) {
            Promise.longStackTraces();
        } else if (!opts.longStackTraces && Promise.hasLongStackTraces()) {
            disableLongStackTraces();
        }
    }
    if ("warnings" in opts) {
        var warningsOption = opts.warnings;
        config.warnings = !!warningsOption;
        wForgottenReturn = config.warnings;

        if (util.isObject(warningsOption)) {
            if ("wForgottenReturn" in warningsOption) {
                wForgottenReturn = !!warningsOption.wForgottenReturn;
            }
        }
    }
    if ("cancellation" in opts && opts.cancellation && !config.cancellation) {
        if (async.haveItemsQueued()) {
            throw new Error(
                "cannot enable cancellation after promises are in use");
        }
        Promise.prototype._clearCancellationData =
            cancellationClearCancellationData;
        Promise.prototype._propagateFrom = cancellationPropagateFrom;
        Promise.prototype._onCancel = cancellationOnCancel;
        Promise.prototype._setOnCancel = cancellationSetOnCancel;
        Promise.prototype._attachCancellationCallback =
            cancellationAttachCancellationCallback;
        Promise.prototype._execute = cancellationExecute;
        propagateFromFunction = cancellationPropagateFrom;
        config.cancellation = true;
    }
    if ("monitoring" in opts) {
        if (opts.monitoring && !config.monitoring) {
            config.monitoring = true;
            Promise.prototype._fireEvent = activeFireEvent;
        } else if (!opts.monitoring && config.monitoring) {
            config.monitoring = false;
            Promise.prototype._fireEvent = defaultFireEvent;
        }
    }
    return Promise;
};

默认 长堆栈跟踪、警告、监控和取消 都被禁用，方法是将它们 false 放在生产环境中。当在开发环境中打开调试器时，它们会被检测到并自动启用。

我建议你再bluebird's documentation 一遍。

Promise.config

Promise.config(Object {
    warnings: boolean=false,
    longStackTraces: boolean=false,
    cancellation: boolean=false,
    monitoring: boolean=false
} options) -> Object;

配置长堆栈跟踪、警告、监控和取消。请注意，即使 false 是此处的默认设置，也可能会检测到自动启用长堆栈跟踪和警告的开发环境。

Promise.config({
    // Enable warnings
    warnings: true,
    // Enable long stack traces
    longStackTraces: true,
    // Enable cancellation
    cancellation: true,
    // Enable monitoring
    monitoring: true
});

您可以配置检查忘记 return 语句的警告 wForgottenReturn:

Promise.config({
    // Enables all warnings except forgotten return statements.
    warnings: {
        wForgottenReturn: false
    }
});

wForgottenReturn 是唯一可以单独配置的警告类型。对应的环境变量key为BLUEBIRD_W_FORGOTTEN_RETURN.

在 Node.js 中，您可以使用环境变量为整个过程配置警告和长堆栈跟踪：

BLUEBIRD_LONG_STACK_TRACES=1 BLUEBIRD_WARNINGS=1 node app.js

如果设置了 BLUEBIRD_DEBUG 环境变量或者 NODE_ENV 环境变量等于 "development".

，则这两个功能将自动启用

使用值 0 将明确禁用某个功能，尽管在调试环境中否则会激活它：

# Warnings are disabled despite being in development environment
NODE_ENV=development BLUEBIRD_WARNINGS=0 node app.js

您可能想从 bluebird 的一位贡献者

那里查看此 official source

Bluebird 被遗忘 return 警告丢失

Bluebird forgotten return warning is missing

javascript

node.js

bluebird

Promise.config