Schema.options.toObject.transform runs for every findOne query

I am running “mongoose@6.0.9” and Node@14.17.6

Do you want to request a feature or report a bug?

I believe it is a bug given that this behaviour wasn’t present in 5.11.11

What is the current behavior?

When creating schema, I am using the toObject.transform options to strip fields like __v before presenting to users. I have noticed that whenever I set a toObject.transform function, it runs in all findOne queries

If the current behavior is a bug, please provide the steps to reproduce.

My code:

const schema = new mongoose.Schema({
  name: String,
  place: String
});

 if (!schema.options.toObject) schema.options.toObject = {};
schema.options.toObject.transform = function (doc, ret, options) {
     console.log('ret:', ret)
     delete ret.__v;
     delete ret.place;
     return ret;
 }

const model = mongoose.model("Model", schema);

async function findDocument() {
  await model.create({name: "Abel", place:"Istanbul"})
  const test= await model.findOne({name: "Abel"});
  
  console.log(test) // returns  object with _id and name. I need to prevent transform from running
}
With the transform function commented out, findOne query returns a Mongo document complete with fields

[deistermatheus]

Update

I found out that console.log(test.place) still returns Istanbul, but console.log(test) returns an object without the place field. Any ideas why it is so?

Your transform does not apply to the underlying document, only to method calls targeting .toObject() or .toJSON(). Logging the top-level object applies the transform, but logging a property does not.

It is likely that logging a document calls toObject under the hood, but I haven’t checked the source code to point out exactly where.

   const test= await model.findOne({name: "Abel"}) // will have all fields and be an instance of mongoose.document
   const test= await model.findOne({name: "Abel"}).toObject() // will be a plain javascript object and will remove fields according to transform

[vkarpov15]

@deistermatheus is right, console.log(test) calls the transform implicitly, here’s the relevant code in Mongoose. console.log() calls require('util').inspect(), which looks for the inspect() function. So this is expected behavior. transform is not called on findOne().