Type issues on using $in mikro orm mongodb

Question

I am using mikro orm with mongodb for my project. So far it's the best orm for MongoDB in typescript. But I am facing type errors on using $in with Object Id. Here's my code:

  @Query(() => [Post])
  async allPosts(@Ctx() { em }: appContext) {
    const posts = await em.find(Post, {});
    const repo = em.getRepository(Post)
    const multiplePosts = await repo.find({ _id: { $in: [new ObjectId("6005d0c253e2b72af07fc61a")] }  });
    console.log("multiplePosts: ", multiplePosts);
    return posts;
}

Post.ts

export class Post {

  @Field(() => ID)
  @PrimaryKey()
  _id!: string;

  @Field(() => String)
  @Property()
  createdAt = new Date();

  @Field(() => String)
  @Property({ onUpdate: () => new Date() })
  updatedAt = new Date();

  @Field(() => String)
  @Property()
  title!: string;

  @Field(() => String)
  @Property()
  excerpt!: string;

  @Field(() => String)
  @Property()
  content!: string;

  @Field()
  @ManyToOne()
  author!: User;
}

Here's the error I am getting:

src/resolvers/PostResolver.ts:32:43 - error TS2769: No overload matches this call.
  Overload 1 of 2, '(where: FilterQuery<Post>, options?: FindOptions<Post, any> | undefined): Promise<Post[]>', gave the following error.      
    Argument of type '{ _id: { $in: ObjectId[]; }; }' is not assignable to parameter of type 'FilterQuery<Post>'.
      Types of property '_id' are incompatible.
        Type '{ $in: ObjectId[]; }' is not assignable to type 'string | RegExp | OperatorMap<FilterValue2<string>> | FilterValue2<string>[] |n 
ull | undefined'.
          Types of property '$in' are incompatible.
            Type 'ObjectId[]' is not assignable to type 'FilterValue2<string>[]'.
              Type 'ObjectId' is not assignable to type 'FilterValue2<string>'.
                Type 'ObjectId' is missing the following properties from type 'RegExp': exec, test, source, global, and 13 more.
  Overload 2 of 2, '(where: FilterQuery<Post>, populate?: any, orderBy?: QueryOrderMap | undefined, limit?: number | undefined, offset?: number | undefined): Promise<...>', gave the following error.
    Argument of type '{ _id: { $in: ObjectId[]; }; }' is not assignable to parameter of type 'FilterQuery<Post>'.
      Types of property '_id' are incompatible.
        Type '{ $in: ObjectId[]; }' is not assignable to type 'string | RegExp | OperatorMap<FilterValue2<string>> | FilterValue2<string>[] | null | undefined'.
          Types of property '$in' are incompatible.
            Type 'ObjectId[]' is not assignable to type 'FilterValue2<string>[]'.

32     const multiplePosts = await repo.find({
                                             ~
33       _id: { $in: [new ObjectId("6005d0c253e2b72af07fc61a")] },
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
34     });
   ~~~~~


    at createTSError (D:\blog\server\node_modules\ts-node\src\index.ts:513:12)
    at reportTSError (D:\blog\server\node_modules\ts-node\src\index.ts:517:19)
    at getOutput (D:\blog\server\node_modules\ts-node\src\index.ts:752:36)
    at Object.compile (D:\blog\server\node_modules\ts-node\src\index.ts:968:32)
    at Module.m._compile (D:\blog\server\node_modules\ts-node\src\index.ts:1056:42)
    at Module._extensions..js (node:internal/modules/cjs/loader:1137:10)
    at Object.require.extensions.<computed> [as .ts] (D:\blog\server\node_modules\ts-node\src\index.ts:1059:12)
    at Module.load (node:internal/modules/cjs/loader:973:32)
    at Function.Module._load (node:internal/modules/cjs/loader:813:14)
    at Module.require (node:internal/modules/cjs/loader:997:19)

Removing the ObjectId makes the typescript compiler happy, but then MongoDB is not treating them as Object ID.

Edited: Also, adding //ts-ignore works fine, so it's a type issue.

Answer 1

The issue comes from your entity definition, where you are explicitly saying that the _id type is string, not ObjectId. So if it is an object id, fix the definition:

  @PrimaryKey()
  _id!: ObjectId;

Then your query should pass. Note that you can also define serialized PK id: string that will act as a virtual getter for the string version of the ObjectId.

https://mikro-orm.io/docs/usage-with-mongo/

You might need to install @types/mongodb.

In general if the property type is ObjectId, it is possible to query by string form too. Those should be equal:

repo.find({ _id: { $in: [new ObjectId("6005d0c253e2b72af07fc61a")] } });
repo.find({ _id: { $in: ["6005d0c253e2b72af07fc61a"] } });
repo.find({ _id: [new ObjectId("6005d0c253e2b72af07fc61a")] });
repo.find({ _id: ["6005d0c253e2b72af07fc61a"] });
repo.find([new ObjectId("6005d0c253e2b72af07fc61a")]);
repo.find(["6005d0c253e2b72af07fc61a"]);

Also note that unless you are using ts-morph, you should be putting explicit types where you use property initializer:

  @Property()
  createdAt: Date = new Date();

https://mikro-orm.io/docs/metadata-providers/#limitations-and-requirements