Mongoose does not recognized "discriminated" subdoc's fields

[OoDeLally]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

I have a base RootDoc with an embedded subDoc: SubDoc.
The SubDoc is "discriminated", with child classes FooSubDoc and BarSubDoc.

When querying on child subdoc's fields e.g. subDoc.fooId, mongoose does not recognize the field, even when it exists on FooSubDoc.
Therefore, if strict=true the filter will be stripped off. If strict=throw (my favorite), it will throw. strict=false works, but I would rather not use it.

I found a trick on stackoverflow topics to have the creation work:

RootDocSchema.path('subDoc').discriminator(SubDocKind.Foo, FooSchema);
RootDocSchema.path('subDoc').discriminator(SubDocKind.Bar, BarSchema);

Doing so makes mongoose accept the subdoc fields during creation.

But it doesnt seem to make it accept the subdoc fields during querying.

In @nestjs/mongoose it seems like the way to bind child classes to their base class is to use the discriminator list in Mongoose.forFeature. I tried it without success.

MongooseModule.forFeature([
      { name: RootDoc.name, schema: RootDocSchema },
      { name: ISubDoc.name, schema: ISubDocSchema, discriminators: [
        { value: SubDocKind.Foo, schema: FooSchema, name: FooSubDoc.name  },
        { value: SubDocKind.Bar, schema: BarSchema, name: BarSubDoc.name  },
      ] },
    ]),

Minimum reproduction code

https://github.com/OoDeLally/nestjs-mongoose-discriminator-strict-bug

Steps to reproduce

1. yarn
2. yarn start:debug

Expected behavior

The fields should be recognized as a possible path.

Package version

9.2.0

mongoose version

6.6.0

NestJS version

9.0.11

Node.js version

14.20.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

No response

[kamilmysliwiec]

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