Feathers: How to cancel hook chain

[kfern]

Steps to reproduce

I have this test before hook:

module.exports = function (options = {}) { // eslint-disable-line no-unused-vars
    const hookTest = function() {
      return function(hook) {
        return hook.app.service('myservice').find({
          query: {
            name: hook.data.name
          }
        })
        .then(result => {
          if (result.data.length === 1){
            return Promise.resolve(hook);//Works fine
          } else {
            throw 'PCU'; //throw an error. Record must exist
          }
        })
        .catch(error => {
            throw new errors.BadRequest(error, { datos: hook.data });
            //UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): BadRequest: PCU
        });
      };
    };
};

Expected behavior

Cancel hook chain without UnhandledPromiseRejectionWarning

Actual behavior

UnhandledPromiseRejectionWarning

System configuration

Module versions (especially the part that's not working):
feathers-cli version 2.2.1

NodeJS version:
v6.9.2

[claustres]

Don't know if this helps but if you'd like to stop the hook chain without raising an error you can simply set the result like this: hook.result = xxx. However if you'd like to raise an error simply throw a Feathers error directly in your then statement:

if (xxx) {
  throw new errors.BadRequest('PCU')
}

Seems to be expected behaviour since you raise an error in your catch that is not catched at a higher level.

[daffl]

You could set hook.cancelled = true and then wrap everything that should into a iff hook checking iff(hook => !hook.cancelled, otherHooks)

[kfern]

@claustres @daffl Thank you. I'll try later.

According to https://docs.feathersjs.com/api/hooks.html#hook-functions, a hook can thow an error or rejects with an error. Should the documentation be changed?

[kfern]

@claustres Setting context.result prevents the DB call. It does not prevent the remaining before & after hooks from running (https://github.com/feathersjs/feathers-hooks-common/issues/236).

@claustres If "raise an error simply throw a Feathers error directly in your then statement", I get UnhandledPromiseRejectionWarning too

@daffl hook.cancelled = true and iff(hook => !hook.cancelled, otherHooks) works, but the operation is done in the database.

Would I need to mix both options? (setting context.result AND iff(hook => !hook.cancelled, otherHooks))

[claustres]

The problem is that in your catch you throw again and this error will not get catched by anyone if you don't have a higher catch block in your app, so the UnhandledPromiseRejectionWarning will eventually popup. For me the 2 throws are redondent. As far as I understand hooks can throw errors but you have to catch them at higher level if you don't want to have the UnhandledPromiseRejectionWarning.

What I can tell is that in my case I use a before hook to check for permissions. When the check fails on a create for instance I throw an error and set the result to null. Don't know which of both things does the job (or if it is actually a mix) but the object is not created in DB neither other hooks are ran.

[kfern]

@claustres Thank you. Next week I will do several tests and I will share the result

[kfern]

I have generated a new app using feathers-cli with 1 service and 1 hook. Code is here: https://github.com/kfern/feathers-issues/tree/feathers-issues-635

In generated hook source comments "Hooks can either return nothing or a promise" and return a promise. Generated hook test only check if the hook returns a Promise.

@daffl Can a hook only return a promise?

[claustres]

Yes a hook can return a promise only, this is the main behaviour for async hooks https://docs.feathersjs.com/api/hooks.html#asynchronous-hooks, if you don't have such async operations you can return nothing at all. In both cases what you do usually is simply to alter the hook object (typically hook.dataor hook.params).

[eddyystop]

A hook can return either a value (the new hook object) or a promise because promises consider values as resolved promises.

So return {} and return Promise.resolve({}) are eqivalent.

[daffl]

Closing since I think all questions should be answered. To skip a hook setting hook.cancelled and checking for iff(hook => !hook.cancelled, otherHooks), to skip the database call hook.result can be set in a before hook.

[lock[bot]]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue with a link to this issue for related bugs.