Edit: to be more clear - I'm NOT getting warning in example below. I would like to know why and see example code where warning would be printed.

In my Node.js project I'm using [bluebird](http://bluebirdjs.com/) Promises library. I observed some cases where I'm getting following warning: 

> 
> Warning: a promise was created in a handler but was not returned from it
> 
> 
> 

I understand that the problem occurs when there is promise that is not connected to any promise chain.

I'm trying to fully understand how this works and what exactly the problem is in mentioned case. For that purpose I took example from [the documentation](https://github.com/petkaantonov/bluebird/blob/master/docs/docs/warning-explanations.md#warning-a-promise-was-created-in-a-handler-but-was-not-returned-from-it).

Here is example of my code based on the example from the documentation for which I'm not getting any warning:

```
const Promise = require('bluebird');

function getUser() {
    return new Promise(function (resolve, reject) {
        setTimeout(function () {
            console.log('get user');
            resolve('userId');
        }, 4000);
    });
}

function getUserData(userId) {
    new Promise(function (resolve, reject) {
        setTimeout(function () {
            console.log('get user data');
            resolve('userData');
        }, 5000);
    });
}

getUser().then(function(user) {
    getUserData(user);
}).then(function(userData) {
    // userData is undefined as expected
    console.log('Data: ', userData);
});

```

Console output:

```
/usr/local/opt/node@6/bin/node test.js
get user
Data:  undefined
get user data

Process finished with exit code 0

```

Does anyone know why there is no warning in my case and how to reproduce it?

Edit: I'm using Node v6.11.3 and Bluebird 3.1.1

**Based on answer from Pierre Clocher I tried also following**:

```
getUser().then(function(user) {
    getUserData(user);
}).then(function(userData) {
    console.log('Data: ', userData);
    // userData is undefined
    throw new Error();
}).catch(function (error) {
    console.log('error: ', error);
});

```

There was also no any warning.

Console output:

```
/usr/local/opt/node@6/bin/node test.js
get user
Data:  undefined
error:  Error
    at test.js:64:11
    at tryCatcher (/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/node_modules/bluebird/js/release/promise.js:512:31)
    at Promise._settlePromise (/node_modules/bluebird/js/release/promise.js:569:18)
    at Promise._settlePromise0 (/node_modules/bluebird/js/release/promise.js:614:10)
    at Promise._settlePromises (/node_modules/bluebird/js/release/promise.js:693:18)
    at Async._drainQueue (/node_modules/bluebird/js/release/async.js:133:16)
    at Async._drainQueues (/node_modules/bluebird/js/release/async.js:143:10)
    at Immediate.Async.drainQueues (/node_modules/bluebird/js/release/async.js:17:14)
    at runCallback (timers.js:672:20)
    at tryOnImmediate (timers.js:645:5)
    at processImmediate [as _immediateCallback] (timers.js:617:5)
get user data

Process finished with exit code 0

```

**Checking Bluebird.js source**

If someone is more familiar with Bluebird source, i've searched across source and find where there is check for warning ([link to source](https://github.com/petkaantonov/bluebird/blob/master/src/debuggability.js#L440)):

```
if (returnValue === undefined && promiseCreated !== null &&
        wForgottenReturn) {
....

}
var msg = "a promise was created in a " + name +
    "handler " + handlerLine + "but was not returned from it, " +
    "see <link to goo.gl removed>" +
    creatorLine;
promise._warn(msg, true, promiseCreated);

```

Using debugger I checked, *returnValue* was undefined in my case, *wForgottenReturn* flag was set to true but *promiseCreated* was null and hence warning was not printed. I would interpret this like Promise via getUserData(user) in my example was not detected as created/unhandled.