Generated list of another document type as a field?

[iamnbutler]

I'm trying to determine the viability of nesting documents with the current functionality within ContentLayer.

I have ContentType: Foo in content/foo/**, and ContentType: Bar in content/bar/**.

const Foo = defineDocumentType(() => ({
    name: 'Foo',
    filePathPattern: `foo/**/*.mdx`,
    contentType: 'mdx',
    fields: {
        id: {
            type: 'string',
            required: true,
        },
        name: {
            type: 'string',
            required: true,
        }
        // more fields
}})

const Bar = defineDocumentType(() => ({
    name: 'Bar',
    filePathPattern: `bar/**/*.mdx`,
    contentType: 'mdx',
    fields: {
        id: {
            type: 'string',
            required: true,
        },
        name: {
            type: 'string',
            required: true,
        }
        // more fields
}})

I'd like to have something like:

// Foo object

{
    id: 'foo1',
    name: 'Foo1',
    // ... more fields
    // List of bars from content/bar/[id_of_foo]
    bars: [
        {
            id: 'bar1',
            name: 'Bar1'
        },
        {
            id: 'bar2',
            name: 'Bar2'
        },
        // ... more fields
    ]
}

But I specifically don't want to have to handwrite a list of all the bar's that exist; I want that to be generated from the content/bar/[id_of_foo]/** directory.

I'm aware of the reference type:

const Bar = defineNestedType(() => ({
  name: 'Bar',
  filePathPattern: 'content/bar/*.md',
  fields: {
    title: { type: 'string', required: true },
  },
}))

But this outputs a list of strings, not a list of objects.

I can do things post-Contentlayer generation, but ideally, I'd rather have Contentlayer do the whole thing.

Is this currently possible, either via a native field type or by some calculated field type shenanigans? Apologies if this has been asked already; I searched through the discussions and the issues and didn't see anything obvious.