has() / whereHas() fails when custom relationship keys are numeric strings

has() / whereHas() fails when custom relationship keys are numeric strings

Environment

• Laravel: 13.7.0
• mongodb/laravel-mongodb: 5.7.1
• mongodb/mongodb: 2.2.0

Description

has() and whereHas() appear to fail when a relationship uses custom string keys whose values are numeric strings (e.g. "1", "2").

The relationship itself works correctly, but relationship existence queries (has, whereHas) return no results.

Using non-numeric strings (e.g. "item-1") works as expected.

Reproduction

Models

class ParentModel extends Model
{
    public function children()
    {
        return $this->hasMany(ChildModel::class, 'parent_key', 'custom_key');
    }
}

class ChildModel extends Model
{
    public function parent()
    {
        return $this->belongsTo(ParentModel::class, 'parent_key', 'custom_key');
    }
}

Documents

parents

{
    "custom_key": "1"
}

children

{
    "parent_key": "1"
}

Working

ParentModel::first()->children;
ParentModel::first()->children()->count();
ChildModel::where('parent_key', '1')->exists();

All of the above return the expected results.

Failing

ParentModel::has('children')->get();
ParentModel::whereHas('children')->get();

These return an empty collection.

Query log

The generated query contains BSON integers instead of strings:

{
    "custom_key": {
        "$in": [
            { "$numberInt": "1" }
        ]
    }
}

However, the stored values are BSON strings:

{
    "custom_key": "1"
}

Since MongoDB performs strict type matching, the query returns no results.

Additional observation

If the values are changed from numeric strings to non-numeric strings, for example:

{
    "custom_key": "item-1"
}

and

{
    "parent_key": "item-1"
}

then has() and whereHas() work correctly.

This suggests that somewhere during the relationship existence query, numeric strings are being coerced into integers before the $in query is constructed.