mongoose plugin requires first argument of "next" be type of Error

[mocheng]

It cost me hours to figure out bug in below code.

calendarSchema.pre('save'， function(next) {
    if (this.begin_time > this.end_time) {
       return next('begin time should be earlier than end time');
   }

   next();
});

If next is invoked with first argument as object not in Error type, it just silently fail without trigger callback of save.

I believe this should be improved. next can transfer first argument into Error if it is string or else.

[vkarpov15]

Thanks for heads up, sorry finding this bug was such a hassle

[yads]

I was trying to figure out why it was silently failing. Thanks for this.

[alabid]

@yads @mocheng It turns out that this is not a bug but how the hooks npm package is supposed to work. Nevertheless, I agree that this behavior is not straight-forward. Mongoose depends on that package for defining pre and post hooks for validation, saving, and so on.

According to the documentation on the hooks docs page, next(<some string>) should pass <some string> to the next middleware whereas next(new Error(<some string>)) should invoke the error callback. I've written a test here to show that mongoose correctly models/uses the behavior of the hooks package.

[yads]

That's very interesting and definitely a non standard way to use middleware. Thanks for looking into it.

[vkarpov15]

Yeah I agree this is a little bit weird. I'd be open to a discussion to change this behavior.

[vkarpov15]

This is fixed in 3.9.x Not quite fixed, see #3672.