linkingObjects() TS type inference + class-based models

[nlarew]

How frequently does the bug occur?

Always

Description

The Realm.Object.linkingObjects() method, when given a class-based model as a type argument, does not infer the correct TypeScript type for the collection that it returns.

The method does not allow you to specify the class-based model, though this would be a welcome improvement and in line with the API for Realm.objects, useObject, etc.

// ✅ The useObject hook correctly infers the `Post` type based on the class I pass in
const post = useObject(Post, _id)!; // Post & Realm.Object<Post, never>

// ⛔️ This doesn't work - the first arg must be a string - but it would be ideal
const user = post.linkingObjects(User, 'posts')[0]!; // User & Realm.Object<User, never>

// ‍ This runs but it uses the class _name_ as a string and doesn't infer the correct return type
const user = post.linkingObjects('User', 'posts')[0]!; // Realm.Object<unknown, never>

// ‍ This runs and assigns a half correct type but still uses class name + a type cast
const user = post.linkingObjects<User>('User', 'posts')[0]!; // User & Realm.Object<unknown, never>

Stacktrace & log output

No response

Can you reproduce the bug?

Always

Reproduction Steps

1. Create a Realm.Object class with a relationship to another class.

 class Foo extends Realm.Object {
   _id: Realm.BSON.ObjectId,
   name: string;
   bars: Realm.List<Bar>
   
   static schema = {
     name: 'Foo',
     properties: {
       _id: 'objectId',
       name: 'string',
       bars: 'Bar[]',
     },
     primaryKey: '_id',
   };
 }
 
 class Bar extends Realm.Object {
   _id: Realm.BSON.ObjectId,
   name: string;
   
   static schema = {
     name: 'Bar',
     properties: {
       _id: 'objectId',
       name: 'string',
     },
     primaryKey: '_id',
   };
 }

await Realm.open({ schema: [Foo.schema, Bar.schema] })

1. Add objects that instantiate the relationship

realm.write(() => {
  const foo = realm.create(Foo, { _id: new Realm.BSON.ObjectId(), name: "Winnie the Foo Bear" })
  const bar1 = realm.create(Bar, { _id: new Realm.BSON.ObjectId(), name: "Honey" })
  const bar2 = realm.create(Bar, { _id: new Realm.BSON.ObjectId(), name: "Smile" })
  foo.bars.push(bar1)
  foo.bars.push(bar2)
})

1. Get a collection of backlinks for the relationship using linkingObjects()

const bars = realm.objects(Bar);
const bar0 = bars[0]!
// ERROR: Argument of type 'typeof User' is not assignable to parameter of type 'string'.
const linkingFoos = bar0.linkingObjects(Foo, "bars")!;

// BUG: TS Type is not correct
const linkingFoos: Realm.Results<Realm.Object<unknown, never>> = bar0.linkingObjects('Foo', "bars")!;

Version

11.4.0

What services are you using?

Local Database only

Are you using encryption?

No

Platform OS and version(s)

macOS Monterey (12.6.2)

Build environment

No response

Cocoapods version

No response

[kneth]

@nlarew Thank for reporting. I agree, that the TS types for linkingObjects() need an update (by looking at https://github.com/realm/realm-js/blob/master/types/index.d.ts#L363

[papafe]

This has been fixed with #5487