Bluebird promise is undefined?

Question

I'm using node 4.5+ and bluebird. I have the following code I intend to use with then:

var checkdir = function(directory) {
    return new Promise(function(resolve, reject) {
        fs.statAsync(directory).then(function() {
            resolve(true);
        }).catch(function(err) {
            if(err.code === 'ENOENT') {
                fs.mkdirAsync(directory).then(function() {
                    resolve(true);
                }).catch(function() {
                    reject(new Error('Can not create folder'));
                });
            } else {
                reject(new Error('Unknown fs stat error: ' + err));
            }
        });
    });
};

Async functions are from fs-extra-promise module. However, when I try to use this function, I get Unhandled rejection Error: Unknown error: TypeError: Cannot read property 'then' of undefined.

Calling:

                checkdir(dir).then(function() {
                    ...
                }).catch(function(err) {
                    reject(new Error('Unknown error: ' + err));
                });

What is wrong here?

That's weird, your code runs find in a snippet without bluebird. How do you implement the library? — Randy, Sep 12 '16 at 09:01
See http://stackoverflow.com/questions/23803743/what-is-the-explicit-promise-construction-antipattern-and-how-do-i-avoid-it — Benjamin Gruenbaum, Sep 12 '16 at 09:01
Any indication (stack trace) of which `.then` the error is referring to? — Jaromanda X, Sep 12 '16 at 09:29
@Tomalak not sure what you mean but feel free to edit and fix it. — Benjamin Gruenbaum, Sep 12 '16 at 10:19

score 3 · Accepted Answer · edited May 23 '17 at 12:08

3

Using any kind of "exists" check in filesystem operations is actively discouraged in the node documentation. (Whether you do the exists check with stat or with exists is irrelevant.)

That means, in addition to Benjamin Gruenbaum's comment regarding the improper use of promises in general in your code, there is another important point to make:

The right way to create a directory is by calling mkdir unconditionally and ignoring EEXIST (compare this answer for more context).

var fs = Promise.promisifyAll(fs);

var ensureDir = function ensureDir(path) {
    return fs.mkdirAsync(path).catch((err) => { if (err.code !== 'EEXIST') throw err; });
}

You can use the mkdirp module to create a path recursively, like mkdir -p would.

edited May 23 '17 at 12:08

Community

1
1

answered Sep 12 '16 at 09:29

Tomalak

332,285
67
532
628

I've changed code but still getting an error: `Unhandled rejection Error: Unknown error: TypeError: Cannot read property 'then' of undefined`. Can it be another promise rejection? – user37741 Sep 12 '16 at 10:45
There is no `.then()` in my code, so the you see error has nothing to do with it. – Tomalak Sep 12 '16 at 11:08
1

I had another promise spoiling the return result for whole chain. Thank you! – user37741 Sep 13 '16 at 17:27

Bluebird promise is undefined?

1 Answers1

Linked