fix: improve DeepPartial type (#8187)

* test: DeepPartial with generics

* fix: resolve DeepPartial generic not matching valid input

* fix: resolve TS errors due to DeepPartial change

* deep partial type simplification

Co-authored-by: Umed Khudoiberdiev <pleerock.me@gmail.com>

src/common/DeepPartial.ts

@@ -1,9 +1,6 @@
 /**
  * Same as Partial<T> but goes deeper and makes Partial<T> all its properties and sub-properties.
  */
-export type DeepPartial<T> = {
-    [P in keyof T]?:
-        T[P] extends Array<infer U> ? Array<DeepPartial<U>> :
-        T[P] extends ReadonlyArray<infer U> ? ReadonlyArray<DeepPartial<U>> :
-        DeepPartial<T[P]> | T[P]
-};
+export type DeepPartial<T> = T extends object ? {
+    [P in keyof T]?: DeepPartial<T[P]>;
+} : T;

src/entity-manager/EntityManager.ts

@@ -247,7 +247,7 @@ export class EntityManager {
             return metadata.create(this.queryRunner);
 
         if (Array.isArray(plainObjectOrObjects))
-            return plainObjectOrObjects.map(plainEntityLike => this.create(entityClass as any, plainEntityLike));
+            return (plainObjectOrObjects as DeepPartial<Entity>[]).map(plainEntityLike => this.create(entityClass, plainEntityLike));
 
         const mergeIntoEntity = metadata.create(this.queryRunner);
         this.plainObjectToEntityTransformer.transform(mergeIntoEntity, plainObjectOrObjects, metadata, true);

test/github-issues/2904/entity/Comment.ts

@@ -0,0 +1,12 @@
+import {
+    Column,
+    CreateDateColumn,
+} from "../../../../src";
+
+export class Comment {
+    @CreateDateColumn()
+    createdAt: Date;
+
+    @Column()
+    savedBy: string;
+}

test/github-issues/2904/issue-2904.ts

@@ -0,0 +1,14 @@
+import {DeepPartial} from "../../../src";
+import {Comment} from "./entity/Comment";
+
+describe("github issues > #2904 Type DeepPartial issue when used with generics", () => {
+
+    it("DeepPartial should correctly handle generics", () => {
+        function commentFactory<E extends Comment>(entity: DeepPartial<E>) {
+            entity.createdAt = new Date();
+            entity.savedBy = 'SomeUSer';
+        }
+
+        commentFactory({});
+    });
+});

test/github-issues/7079/issue-7079.ts

@@ -30,22 +30,22 @@ describe("github issues > #7079 Error when sorting by an embedded entity while u
                 id: 1,
                 text: "Happy Holidays",
                 userId: 1,
-                blog: { date: new Date().toISOString() },
-                newsletter: { date: new Date().toISOString() }
+                blog: { date: new Date() },
+                newsletter: { date: new Date() }
             },
             {
                 id: 2,
                 text: "My Vacation",
                 userId: 1,
-                blog: { date: new Date().toISOString() },
-                newsletter: { date: new Date().toISOString() }
+                blog: { date: new Date() },
+                newsletter: { date: new Date() }
             },
             {
                 id: 3,
                 text: "Working with TypeORM",
                 userId: 2,
-                blog: { date: new Date().toISOString() },
-                newsletter: { date: new Date().toISOString() }
+                blog: { date: new Date() },
+                newsletter: { date: new Date() }
             }
         ]
         await postRepo.save(posts);