"minimize: false" is not working for it's own field

[kuehn-sba]

I have opened a new issue because Schema.Types.Mixed minimize: false not working #15177

cannot be reopened, but it is related and relevant and also reproducible.

No. It's a critical issue.

And you have to make a distinction here. “minimize: false” actually worked in mongoose5.x in such a way that it also affected the own object in the database and was not only allowed for all sub-objects. So you could also save the one field where minimize: false was directly as an empty object.

And secondly, the whole thing has been buggy since at least mongoose 7.x - possibly even 6.x. If the field is set to minimize: false and you try to save a new document (e.g. new MySchema(osbj).save()), then no empty object is created.

If, on the other hand, you save the field for an existing document (obj.save()), the empty object is saved! (as it was in mongoose5.x)

To make matters worse, it seems that you cannot read these empty objects in mongoose 7.x (in mongoose 5.x you can)
For me, the minimize: false feature has been properly bugged since the use of mongoose 7.x, which currently has to be productively modified unnecessarily by means of a workaround.

Originally posted by @kuehn-sba in #15177

[vkarpov15]

@kuehn-sba please follow the issue template. Include a repro script, Mongoose versions, etc.

[kuehn-sba]

@kuehn-sba please follow the issue template. Include a repro script, Mongoose versions, etc.

Where to find? Every detail about the minimize: false bug is described exactly here (detailed)!
but here we go:

Version:
Mongoose Version: 7.x
(possibly even already Mongoose 6.x)

Schema example:

var MySubSchema = new Mongoose.Schema({
},{ _id : false, minimize: false });

var MySchema = new Mongoose.Schema({

myfield:  MySubSchema

});

Test (Create):

var obj = {
myfield: {}
}

new MySchema(obj).save()) // no empty field is created.

Test (Update):
obj.save(); // stores empty field

Test (Find):
obj.find(); // ignores empty field

Expected:
it should be possible to create, save and at least read out (by find,..) an empty field like before in mongoose 5.x

Note: This is not about the handling of nested objects by minimize: false (as often discussed), but specifically about the minimize: false behaviour of the own field (e.g. myfield) itself. Note that this worked in Mongoose Version 5.x, and can generally be saved in mongo db in this way - regardless of the mongo version.

[vkarpov15]

The issue is that you're setting minimize: false on MySubSchema but not MySchema. minimize: false only affects subpaths of MySubSchema. Add minimize: false to the top-level schema as follows: const MySchema = new mongoose.Schema({ myfield: { type: MySubSchema } }, { minimize: false }).

Mongoose 5 didn't minimize myfield regardless of whether MySchema had minimize: false. This was a bug.

Is adding minimize: false to top-level schema sufficient for your use case?

[kuehn-sba]

Mongoose 5 didn't minimize myfield regardless of whether MySchema had minimize: false. This was a bug.

No, Mongoose 5 correctly recognizes the minimize: false flag for its own field. I don't think it's a bug, but is actually already handled correctly in Mongoose 5. Especially as MongoDB also allows individual empty objects. It feels more like from a certain Mongoose version (6.x?, 7.x) the behavior only applies to nested fields (But then unfortunately for all of them!).

Is adding minimize: false to top-level schema sufficient for your use case?

No, because all other fields must not be empty in my schema. I basically need 1 special field as an empty object (since I'm passing it through 1:1 for another API), but not all fields are allowed to be empty. Right now I just solve it via a nested fake field within myfield - I just leave it out in processing, but it doesn't make much sense in the code to have to do it that way, but in the end it works.

To cut a long story short:
If only all or none (nested) elements for a specific field can be written as empty controlled by the minimize: false flag then certain use cases, e.g. that only one single field may be empty (but not all), as in my case, are excluded.

It's not totally critical, since I can work around it by using a fake child element (inside myfield and not using this minimize:false-feature), but since the architecture of our system was designed with Mongoose 4.x since the beginning, it is now a limitation in handling, especially since, as mentioned above, the Create, Update and Find methods work differently to want to use this feature for a single field.

[vkarpov15]

As a workaround, you can mark myfield as required: true, that will prevent Mongoose from minimizing it out. We're working on a fix.

var MySchema = new Mongoose.Schema({
  myfield:  { type: MySubSchema, required: true } // <-- required: true means Mongoose won't minimize out empty objects
});