Mongoose build error with latest TypeScript 'Type of property 'defaultProps' circularly references itself in mapped type'

[NenadJovicic]

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

What is the current behavior?
I create Document for Schema and I type some property as that Document. Then I get a build error that type got a reference to itself. Same issue with some other libraries could be found here microsoft/TypeScript#37597

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

import { Document, HookErrorCallback, Schema } from "mongoose";

export const UserSchema: Schema = new Schema({
  friend: {
    type: Schema.Types.ObjectId,
    ref: "user",
  },
  someString: {
    type: Schema.Types.String,
  },
  updatedAt: {
    type: Schema.Types.Date,
  },
});

UserSchema.pre("save", function (next: HookErrorCallback): any {
  (this as UserDoc).updatedAt = new Date(); // on this line, it throws an error that `friend` circularly reference itself
  return next();
});

// if I don't extend `Document` there is no build error, so it is linked with mongoose.Document
export interface UserDoc extends Document {
  // typing it as UserDoc because it would be populated
  friend: UserDoc;
  someString: string;
  updatedAt: Date;
}

This is tsconfig.json

{
    "compilerOptions": {
        "module": "commonjs",
        "declaration": false,
        "noImplicitAny": false,
        "removeComments": true,
        "noLib": false,
        "emitDecoratorMetadata": true,
        "experimentalDecorators": true,
        "target": "es6",
        "sourceMap": true,
        "allowJs": true,
        "outDir": "./build",
        "baseUrl": "./src"
    },
    "include": ["."],
    "exclude": ["./node_modules"]
}

This is package.json file

{
  "name": "mongoose-typescript-error",
  "version": "1.0.0",
  "description": "Demo project to provide example of error with typescript",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "build": "tsc"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "mongoose": "5.11.11"
  },
  "devDependencies": {
    "ts-node": "9.1.1",
    "typescript": "4.1.3"
  }
}

It is enough to run npm run build and to get an error in terminal
What is the expected behavior?
Expected behavior is that build will pass without any errors.

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
Node.js: 12.13.0
Mongoose: 5.11.11 (tried also with 5.11.15, same thing)
MongoDB: 3.6

[vkarpov15]

We'll likely have a better approach to this with #9818, but the workaround here is to use a union type because friend can be either a user or an ObjectId:

import { Document, HookErrorCallback, Schema, Types } from "mongoose";
  
export const UserSchema: Schema = new Schema({
  friend: {
    type: Schema.Types.ObjectId,
    ref: "user",
  },
  someString: {
    type: Schema.Types.String,
  },
  updatedAt: {
    type: Schema.Types.Date,
  },
});

UserSchema.pre("save", function (next: HookErrorCallback): any {
  (this as UserDoc).updatedAt = new Date();
  ((this as UserDoc).friend as UserDoc).someString.trim();
  return next();
});

export interface UserDoc extends Document {
  friend: Types.ObjectId | UserDoc;
  someString: string;
  updatedAt: Date;
}