Virtual Populate foreignField is array in combination with UUIDs

[JustDoItSascha]

Hello,

I have the exact same issue @Namchee had in this other issue. The query which Mongoose performs is correct, it would return the correct documents from the foreign schema. But it seems like it's not getting merged correctly afterwards...

Problem exists with Mongoose 8.12.0

P.S. I found out, it's only happening when using UUIDs instead of ObjectId.

All of the cases here refers to array of IDs in virtualized-schema to ID in reference schema. But, what if I have the opposite case?

Example:

Announcement Schema

const announcementSchema = new Schema({

  title: {

    type: String,

    trim: true,

    unique: true,

    required: true,

    maxlength: 25,

  },



  content: {

    type: String,

    trim: true,

    required: true,

    maxlength: 500,

  },



  validUntil: {

    type: Date,

    required: true,

  },



  important: {

    type: Boolean,

    default: false,

  },



  categories: {

    type: [Schema.Types.ObjectId],

    ref: 'Category',

    default: [],

  },

});

Category Schema

const categorySchema = new Schema({

  name: {

    type: String,

    trim: true,

    required: true,

    index: true,

    maxlength: 50,

  },



  desc: {

    type: String,

    trim: true,

    required: true,

    maxlength: 250,

  },

});



categorySchema.virtual('announcementCount', {

  ref: 'Announcement',

  localField: 'id',

  foreignField: 'categories',

  count: true,

});

I've tried the above solution, but I keep getting undefined when I tried to access announcementCount after populating it.

Originally posted by @Namchee in #4585

[JustDoItSascha]

Ok, I found out, that the error is in this line:

https://github.com/Automattic/mongoose/blob/master/lib/helpers/populate/assignRawDocsToIdStructure.js#L81

The ID is in Binary Format, one need to call toUUID() instead of String() then it would work. But I'm not sure if this is the correct place to do it? Maybe the root cause is already before? Maybe it needs to be something like

sid = typeof id.toUUID === 'function' ? id.toUUID() : String(id); ?

[JustDoItSascha]

Edit: My quick fix is destroying other populations which are not virtual. So it's wrong. It seems like the rawDocs are having string keys.

I could only fix it by changing line 81 of assignRawDocsToldStructure to

sid = id.toString('hex').replace(
        /^(.{8})(.{4})(.{4})(.{4})(.{12})$/,
        '$1-$2-$3-$4-$5'
    )

and line 4715 of model.js to

key = _val.toString('hex').replace(
            /^(.{8})(.{4})(.{4})(.{4})(.{12})$/,
            '$1-$2-$3-$4-$5'
        );

But this will not work with ObjectIds anymore. I know what the error is, but I have no idea how to fix it properly, because I don't know why it's sometimes a Buffer, sometimes a Binary... :(