Error when using recursive populate on mongoose document element with empty array

[Creiger]

Steps to reproduce

Create 3 mongoose documents with references ex. channels,users,groups. Channel can have 0:n users, user can have 0:1 groups. Channels schema has users defined like this:
users: [{type: mongooseClient.Schema.Types.ObjectId, ref: 'users', required: true}]
so when you create new Channel document, without any users, mongoose adds by design
users: []
to new document. Then add populate schema to channel hooks
include: { service: 'users', nameAs: 'users', parentField: 'users', childField: '_id', include: [ { service: 'groups', nameAs: 'group', parentField: 'group', childField: '_id' } ] }
and then fetch channels.

You will get an error:

Cannot read property 'toJSON' of null
error: TypeError: Cannot read property 'toJSON' of null
at populateItemArray (/data/www/lukashronec.cz/ptt/node_modules/feathers-hooks-common/lib/services/populate.js:108:12)
at /data/www/lukashronec.cz/ptt/node_modules/feathers-hooks-common/lib/services/populate.js:234:14
at process._tickCallback (internal/process/next_tick.js:103:7)

I also tried non recursive populate with users only and it worked. When i remove those Channels users where they are empty, it works with recursive schema. So only recursive population has problem with empty arrays.

Expected behavior

I would expect that populateItemArray would check if items are an empty array and return again an empty array. Same when i use non recursive populate schema.

Actual behavior

It throws an error.

System configuration

Tell us about the applicable parts of your setup.

"feathers": "^2.1.2",
"feathers-authentication": "^1.2.3",
"feathers-authentication-hooks": "^0.1.3",
"feathers-authentication-jwt": "^0.3.1",
"feathers-authentication-local": "^0.3.4",
"feathers-configuration": "^0.4.1",
"feathers-errors": "^2.8.0",
"feathers-hooks": "^2.0.1",
"feathers-hooks-common": "^3.3.2",
"feathers-mongoose": "^5.1.0",
"feathers-rest": "^1.7.2",
"feathers-socketio": "^2.0.0",

[eddyystop]

You will find your issues might be handled faster is they are posted to the repo they affect, feathers-hooks-common in this case.

Preliminaries for fix are in feathersjs-ecosystem/feathers-hooks-common#190

[eddyystop]

I think you would want to use asArray in this case to ensure you always get an array back, even if it has just 1 element. It looks like that would avoid the problem until a fix lands.

include: {
  service: 'users',
  nameAs: 'users',
  parentField: 'users',
  childField: '_id',
  asArray: true, // workaround
  include: [ ... ]
}

[eddyystop]

Fixed in feathersjs-ecosystem/feathers-hooks-common#191 which will be published as v3.3.3.

Please confirm the fix works for you. Could you afterwards close this issue? Thanks.

[Creiger]

Thank you eddyystop and sorry for the wrong repo.

[lock]

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.