Querying array of arrays with $elemMatch and $not throws a CastError

[Davian99]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

7.5.2

Node.js version

18.2

MongoDB server version

6.0.5

Typescript version (if applicable)

No response

Description

When querying an array of arrays of strings field using a combination of $elemMatch and $not, mongoose's query casters throws an error.

The query is:
{ arr: { $elemMatch: {$not: {$elemMatch: {$eq: '1'}}} } }

Our intention is to obtain all documents that have one nested array that does not contain certain element (in this case, the string '1').

CastError: Cast to string failed for value "{ '$elemMatch': { '$eq': '1' } }" (type Object) at path "arr" for model "nested_arrays"
  at SchemaString.cast (/home/davids/Documents/MongooseType/node_modules/.pnpm/mongoose@7.5.2/node_modules/mongoose/lib/schema/string.js:606:11)

Steps to Reproduce

This short code shows that the query itself works using mongo itself (using the collection property of the model) and that mongoose throws the cast error:

const mongoose = require('mongoose');

const schema = new mongoose.Schema({
  arr: [[String]],
});

const model = mongoose.model('nested_arrays', schema);

mongoose.connect('mongodb://127.0.0.1:27017', { useNewUrlParser: true, useUnifiedTopology: true })
  .then(async () => {
    const obj = new model({ arr: [[1,2,3], [2,3,4]] })
    await obj.save();

    const query = { arr: { $elemMatch: {$not: {$elemMatch: {$eq: '1'}}} } };
    const mongo_res = await model.collection.find(query).toArray();
    console.log(mongo_res);

    const mongoose_res = await model.find(query);
    console.log(mongoose_res);
  });

The full output is really long, but the first lines are:

[
  {
    _id: new ObjectId("6509bfce3c3c67f9f8e099d6"),
    arr: [ [Array], [Array] ],
    __v: 0
  }
]
/home/davids/Documents/MongooseType/node_modules/.pnpm/mongoose@7.5.2/node_modules/mongoose/lib/schema/string.js:606
    throw new CastError('string', value, this.path, null, this);
          ^

CastError: Cast to string failed for value "{ '$elemMatch': { '$eq': '1' } }" (type Object) at path "arr" for model "nested_arrays"

Expected Behavior

Using the mongoose find should return the same results than the model.collection when using the same query.

[IslandRhythms]

const mongoose = require('mongoose');

const schema = new mongoose.Schema({
  arr: [[String]],
});

const test = mongoose.model('nested_arrays', schema);

async function run() {
  await mongoose.connect('mongodb://127.0.0.1:27017');
  await mongoose.connection.dropDatabase();
  const obj = new test({ arr: [[1,2,3], [2,3,4]] })
    await obj.save();

    const query = { arr: { $elemMatch: {$not: {$elemMatch: {$eq: '1'}}} } };
    const mongo_res = await test.collection.find(query).toArray();
    console.log(mongo_res);

    const mongoose_res = await test.find(query);
    console.log(mongoose_res);
}

run();