TS2589: Type instantiation is excessively deep and possibly infinite

[HamoBoker]

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

What is the current behavior?
i'm generating interfaces using mongoose-tsgen and everything works fine in mongoose <=6.3.1, but on v6.3.2 or v6.3.3 i get this ts error TS2589: Type instantiation is excessively deep and possibly infinite, also im not using @types/mongoose

If the current behavior is a bug, please provide the steps to reproduce.
await SomeModel.findById(id)
you can test example code in mongoose-tsgen

tsconfig.json

{
  "extends": "@tsconfig/node16/tsconfig.json",
  "ts-node": {
    "transpileOnly": true,
    "files": true
  },
  "compilerOptions": {
    "moduleResolution": "Node",
    "outDir": "dist",
    "allowSyntheticDefaultImports": true,
    "declaration": false,
    "removeComments": true,
    "noUnusedLocals": false,
    "newLine": "lf",
    "noImplicitAny": true,
    "pretty": true,
    "noEmitOnError": true
  },
  "include": ["src/**/*.ts"],
  "exclude": ["node_modules/**"]
}

What is the expected behavior?
ts build without errors

Thank you so much for you great work

[IslandRhythms]

import * as mongoose from 'mongoose';
import { UserDocument, UserModel, UserSchema, UserObject} from './src/interfaces/mongoose.gen'

const UserSchema: UserSchema = new mongoose.Schema({
    name: String
});

const User = mongoose.model<UserDocument, UserModel>('User', UserSchema);

async function run() {
    await mongoose.connect('mongodb://localhost:27017');
    await mongoose.connection.dropDatabase();
    const entry = await User.create({ name: 'Test'});
    await User.findById(entry._id);
    console.log('done');
}

run();

tsconfig

{
  "ts-node": {
    "transpileOnly": true,
    "files": true
  },
  "compilerOptions": {
    "moduleResolution": "Node",
    "outDir": "dist",
    "allowSyntheticDefaultImports": true,
    "declaration": false,
    "removeComments": true,
    "noUnusedLocals": false,
    "newLine": "lf",
    "noImplicitAny": true,
    "pretty": true,
    "noEmitOnError": true
  },
  "exclude": ["node_modules/**"]
}

[HamoBoker]

@IslandRhythms thanks for response, I created a new project and i used your snippet, and still get the same error but on schema only

same code in above comment

import * as mongoose from 'mongoose';
import { UserDocument, UserModel, UserSchema, UserObject } from '../interfaces/mongoose.gen'

const UserSchema: UserSchema = new mongoose.Schema({
  name: String
});

const User = mongoose.model<UserDocument, UserModel>('User', UserSchema);

async function run() {
  await mongoose.connect('mongodb://localhost:27017');
  await mongoose.connection.dropDatabase();
  const entry = await User.create({name: 'Test'});
  await User.findById(entry._id);
  console.log('done');
}

run();

package.json

  "dependencies": {
    "mongoose": "^6.3.3"
  },
  "devDependencies": {
    "mongoose-tsgen": "^9.0.5",
    "nodemon": "^2.0.16",
    "ts-node": "^10.7.0",
    "typescript": "^4.6.4"
  }

same tsconfig

{
  "ts-node": {
    "transpileOnly": true,
    "files": true
  },
  "compilerOptions": {
    "moduleResolution": "Node",
    "outDir": "dist",
    "allowSyntheticDefaultImports": true,
    "declaration": false,
    "removeComments": true,
    "noUnusedLocals": false,
    "newLine": "lf",
    "noImplicitAny": true,
    "pretty": true,
    "noEmitOnError": true
  },
  "exclude": ["node_modules/**"]
}

[IslandRhythms]

It must be something with your setup, I can't reproduce it on my end.

[Uzlopak]

Does it also happen when transpiling with tsc? Does it only happen in vscode? Which typescript version do you use in vscode? Which in your project? What happens when you update typescript? What when you update vscode?

[HamoBoker]

Yes, i'm using webstorm but i tested it on vscode also i get same error, on mongoose@6.3.1 everything works fine but its not working on 6.3.2 & 6.3.3

node: v16.15.0
typescript: v4.6.4 (latest) in project & IDE & globally
device: macOS 12.3.1 (M1)

when running tsc command i get this

src/models/User.ts:4:52 - error TS2589: Type instantiation is excessively deep and possibly infinite.

4 const UserSchema: UserSchema = new mongoose.Schema({
                                                     ~
5   name: String
  ~~~~~~~~~~~~~~
6 });
  ~

heres the new project that contains the code snippet above and it produces the problem
node-demo.zip

npm i && npx mtgen

[mohammad0-0ahmad]

By using mongoose v6.3.1 the error will disappear for now.
I guess LeanDocument type "not sure yet" cause this breaking change.
I think @taxilian can help with that.

[IslandRhythms]

I downloaded your zip and ran it and still can't reproduce, it's something with your setup.

[mohammad0-0ahmad]

I downloaded your zip and ran it and still can't reproduce, it's something with your setup.

Hello @IslandRhythms !
I've got it on my setup, can you test it again after restarting VSC?

[IslandRhythms]

Got it

[mohammad0-0ahmad]

Hello @HamoBoker, @jainil, @francescov1!
I've noticed that populate FN overloading in auto generated type "mongoose.gen" is what cause this error with the latest versions.
So you might check that to solve this issue.
I don't think we need to fix this breaking change in mongoose. @IslandRhythms

[francescov1]

Thanks for the ping @mohammad0-0ahmad, I'll look into this over the weekend!

[francescov1]

@HamoBoker This incompatibility is turning out to be a bit tougher to uncover than I expected. For now, you can continue using mongoose-tsgen with the --no-populate-overload flag to resolve the problem (but won't be able to benefit from population inference).

@mohammad0-0ahmad Any idea on the expected timeline for your PR #11563. This PR removes the need for mongoose-tsgen, so depending on when it gets merged it may not be worth trying to fix the issue in mongoose-tsgen.

[mohammad0-0ahmad]

@francescov1 sorry for that, I don't really know when it will be exactly merged, but @vkarpov15 said it will be shipped with the next minor release "6.4.0"

[HamoBoker]

Ok I'll stick with this solution for now

Thank you guys for your great work, I really appreciate it

[vkarpov15]

@francescov1 thanks for looking into this and thanks for the lib, mongoose-tsgen is 👍 . You're right that the populate() override is what causes the "Type instantiation is excessively deep and possibly infinite" error, however, I haven't been able to figure out a way to avoid that error without removing the PopulatedDocument type entirely.

I really like this PopulatedDocument type. Very handy if you're defining your document interfaces using mongoose.Types.ObjectId | ChildDoc. PopulatedDocument is missing a couple of edge cases. For example, it is perfectly fine to populate fields that aren't of type ObjectId, like numbers or strings. We even support populating subdocuments in place.

But, again, this sort of TypeScript bug is very hard to diagnose. We'll keep this open for the future, and consider pulling in the PopulatedDocument abstraction into Mongoose's types.

[francescov1]

@vkarpov15 Thanks for checking this out, too bad there are not any obvious fixes.

Sounds like the PopulatedDocument type may still be useful; I'd be happy to help integrate it into Mongoose if this is the case, let me know! I find it to be quite nice since most of my populate return types are automatically inferred, and if they cannot be then we just fallback to mongoose.Types.ObjectId | ChildDoc.

[francescov1]

@vkarpov15 Can we expect this to be resolved by the Mongoose team, or is this is an issue with mongoose-tsgen? Would like to try getting it resolved soon since its a breaking issue for many users. I havent had any luck fixing it yet, but not sure if I should be focusing on fixing it from my end or from the Mongoose types. Also just finding it hard to track down the root cause since the error is so generic.

[mohammad0-0ahmad]

@francescov1 try to override LeanDocument helper type, I think this issue is related to the changes made on that.

[vkarpov15]

@francescov1 as far as I can tell, this is an issue with mongoose-tsgen. We've been trying to improve the mongoose-tsgen type output, but haven't been able to fix it.

[francescov1]

I just reviewed this again, it seems the issue has been resolved as of Mongoose v6.4.1 (so it only affects Mongoose 6.3.2 - 6.4.0). I think we can close this @HamoBoker @vkarpov15 ?

[HamoBoker]

Yes @francescov1 , and sorry i forgot to close it.

Thank you for the amazing work 💙