[Typescript] rollback some of the change on toJS to avoir circular reference

CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 Dates are formatted as YYYY-MM-DD.
 
+## Unreleased
+
+- [Typescript] rollback some of the change on `toJS` to avoir circular reference
+
 ## [4.2.0] - 2022-12-22
 
 - [TypeScript] Better type for toJS [#1917](https://github.com/immutable-js/immutable-js/pull/1917) by [jdeniau](https://github.com/jdeniau)

type-definitions/immutable.d.ts

@@ -93,24 +93,34 @@
 declare namespace Immutable {
   /**
    * @ignore
+   *
+   * Used to convert deeply all immutable types to a plain TS type.
+   * Using `unknown` on object instead of recursive call as we have a circular reference issue
    */
-  export type DeepCopy<T> = T extends Collection.Keyed<infer KeyedKey, infer V>
+  export type DeepCopy<T> = T extends Record<infer R>
+    ? // convert Record to DeepCopy plain JS object
+      {
+        [key in keyof R]: R[key] extends object ? unknown : R[key];
+      }
+    : T extends Collection.Keyed<infer KeyedKey, infer V>
     ? // convert KeyedCollection to DeepCopy plain JS object
       {
         [key in KeyedKey extends string | number | symbol
           ? KeyedKey
-          : string]: DeepCopy<V>;
+          : string]: V extends object ? unknown : V;
       }
     : // convert IndexedCollection or Immutable.Set to DeepCopy plain JS array
     T extends Collection<infer _, infer V>
-    ? Array<DeepCopy<V>>
+    ? Array<V extends object ? unknown : V>
     : T extends string | number // Iterable scalar types : should be kept as is
     ? T
     : T extends Iterable<infer V> // Iterable are converted to plain JS array
-    ? Array<DeepCopy<V>>
+    ? Array<V extends object ? unknown : V>
     : T extends object // plain JS object are converted deeply
     ? {
-        [ObjectKey in keyof T]: DeepCopy<T[ObjectKey]>;
+        [ObjectKey in keyof T]: T[ObjectKey] extends object
+          ? unknown
+          : T[ObjectKey];
       }
     : // other case : should be kept as is
       T;

type-definitions/ts-tests/deepCopy.ts

@@ -5,23 +5,16 @@ import { List, Map, Record, Set, Seq, DeepCopy, Collection } from 'immutable';
 
   // $ExpectType { a: number; b: number; }
   type Test = DeepCopy<{ a: number; b: number }>;
-  //   ^?
-
-  // $ExpectType number
-  type TestA = Test['a'];
-  //   ^?
 }
 
 {
   // Iterables
 
   // $ExpectType string[]
   type Test = DeepCopy<string[]>;
-  //   ^?
 
   // $ExpectType number[]
   type Keyed = DeepCopy<Collection.Indexed<number>>;
-  //   ^?
 }
 
 {
@@ -30,10 +23,12 @@ import { List, Map, Record, Set, Seq, DeepCopy, Collection } from 'immutable';
   // $ExpectType { [x: string]: string; }
   type StringKey = DeepCopy<Map<string, string>>;
 
-  // $ExpectType { [x: string]: object; }
+  // should be `{ [x: string]: object; }` but there is an issue with circular references
+  // $ExpectType { [x: string]: unknown; }
   type ObjectKey = DeepCopy<Map<object, object>>;
 
-  // $ExpectType { [x: string]: object; [x: number]: object; }
+  // should be `{ [x: string]: object; [x: number]: object; }` but there is an issue with circular references
+  // $ExpectType { [x: string]: unknown; [x: number]: unknown; }
   type MixedKey = DeepCopy<Map<object | number, object>>;
 
   // $ExpectType string[]
@@ -62,9 +57,23 @@ import { List, Map, Record, Set, Seq, DeepCopy, Collection } from 'immutable';
 {
   // Nested
 
-  // $ExpectType { map: { [x: string]: string; }; list: string[]; set: string[]; }
+  // should be `{ map: { [x: string]: string; }; list: string[]; set: string[]; }` but there is an issue with circular references
+  // $ExpectType { map: unknown; list: unknown; set: unknown; }
   type NestedObject = DeepCopy<{ map: Map<string, string>; list: List<string>; set: Set<string>; }>;
 
-  // $ExpectType { map: { [x: string]: string; }; }
+  // should be `{ map: { [x: string]: string; }; }`, but there is an issue with circular references
+  // $ExpectType { map: unknown; }
   type NestedMap = DeepCopy<Map<'map', Map<string, string>>>;
 }
+
+{
+  // Circular references
+
+  type Article = Record<{ title: string; tag: Tag; }>;
+  type Tag = Record<{ name: string; article: Article; }>;
+
+  // should handle circular references here somehow
+  // $ExpectType { title: string; tag: unknown; }
+  type Circular = DeepCopy<Article>;
+  //   ^?
+}

type-definitions/ts-tests/record.ts

@@ -88,6 +88,7 @@ import { List, Map, Record, Set } from 'immutable';
   // $ExpectType { map: Map<string, string>; list: List<string>; set: Set<string>; }
   withMap.toJSON();
 
-  // $ExpectType { map: { [x: string]: string; }; list: string[]; set: string[]; }
+  // should be `{ map: { [x: string]: string; }; list: string[]; set: string[]; }` but there is an issue with circular references
+  // $ExpectType { map: unknown; list: unknown; set: unknown; }
   withMap.toJS();
 }