Relationships missing in virtual resolver callback

Bug report

Describe the bug

I’m not able to access fields of relationship type in virtual field resolver method.

To Reproduce

Create model with relationship field of type many and virtual field that should return number of relationships. But object item.answers is undefined.

fields: {
    question: {
      type: Text,
      isRequired: true,
    },
    stats: {
      type: Virtual,
      resolver: (item) => item.answers.length,
    },
    answers: {
      type: Relationship,
      many: true,
      ref: 'PollAnswer',
    },
  },

If I print content of item object I get only:

{ question: 'New on', __v: 0, id: '5e3179fcf456f0b86ae2dab8' }

System information

• OS: macOS

[timleslie]

This is actually the expected behaviour, although perhaps it’s not well documented. Within a virtual field resolver we don’t necessarily know which relationships the developer will need, nor how deeply nested they might need to access things. Also, an item might have millions of related items, and it would be particularly inefficient to immediately look all of these up if they’re not actually needed. As it is impossible to know, we resist the temptation to guess and simple provide the item as stored in the database (notice the __v field, which is a mongo thing). If you need to access the related items you will need to perform a subsequent graphql query and define the filters and returned fields on the item.

[MadeByMike]

Thanks for this answer Tim, I added this to the virtual field docs: https://github.com/keystonejs/keystone/blob/master/packages/fields/src/types/Virtual/README.md