Any ideas, contributions, improvements for MONGOOSE-LEAN-EXTENSION plugin

[SsekandiRaymond]

MONGOOSE-LEAN-EXTENSION plugin

Why is this mongoose plugin written??

Your mongoose query has .lean() but;

• ObjectId fields are still BSON types (ObjectId) that require manual conversion.
• The __v version key is often unnecessarily present in results.
• Deeply nested ObjectIds in subdocuments aren't stringified without additional effort

Why should you use it?

The plugins extends the .lean() functionality to;

• Auto-stringification of top-level _id fields
• Auto-removal of the __v field
• Optional stringification of nested ObjectId fields via path expressions (e.g. contributors._id)
• If plugin is used globally, mongoose.plugin(require("mongoose-lean-extension")), even populate results will include stringified _id

[vkarpov15]

Cool, thanks for writing this plugin 👍

For record._id = record?._id?.toString();, I'd advise against doing that because _id can be any type. You should check whether _id is an ObjectId in the schema, otherwise you might end up converting numbers to strings.

[SsekandiRaymond]

Thanks, let me update that

…

On Wed, Jun 4, 2025 at 7:29 PM Valeri Karpov ***@***.***> wrote: Cool, thanks for writing this plugin 👍 For record._id = record?._id?.toString();, I'd advise against doing that because _id can be any type. You should check whether _id is an ObjectId in the schema, otherwise you might end up converting numbers to strings. — Reply to this email directly, view it on GitHub <#15460 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BJDTIAWTEM32YDFR3HYQHMT3B4NGHAVCNFSM6AAAAAB6P4UJW6VHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTGMZXGAYDSNQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[yakubka]

The plugin addresses real pain points with .lean() results. A few thoughts on the approach and how to handle the same needs without an extra dependency.

For ObjectId stringification without a plugin:

const doc = await MyModel.findById(id).lean()
// Recursively stringify ObjectIds
function stringifyIds(obj) {
if (!obj || typeof obj !== "object") return obj
if (obj._bsontype === "ObjectId") return obj.toString()
if (Array.isArray(obj)) return obj.map(stringifyIds)
return Object.fromEntries(Object.entries(obj).map(([k, v]) => [k, stringifyIds(v)]))
}
const plain = stringifyIds(doc)

For __v removal you can use the projection:

const doc = await MyModel.findById(id).select("-__v").lean()

Or configure it schema-wide:

const schema = new Schema({ ... }, { versionKey: false })

The transform option in toJSON covers the JSON serialization case but lean() bypasses toJSON entirely, which is why plugins like yours exist. The plugin approach is valid when you need a consistent behavior across many models without modifying each query individually. The main tradeoff is that it adds a dependency and must be updated when Mongoose changes its lean internals.