fix(core): do not merge entity instances in em.create()

Previously `em.create(Book, { tags: [t1, t2] })`, where t1 and t2 are entity instances, did automatically merge those in case
they had PK set. This obviously don't work for composite keys, where we always know the PK.

With this change, only PKs will be converted to references and merged, rest will be considered as new entities.

cherry pick of fe204c6

lib/hydration/ObjectHydrator.ts

@@ -1,6 +1,6 @@
 import { AnyEntity, EntityData, EntityProperty, Primary } from '../typings';
 import { Hydrator } from './Hydrator';
-import { Collection, EntityAssigner, ReferenceType, wrap } from '../entity';
+import { Collection, EntityAssigner, ReferenceType } from '../entity';
 import { Utils } from '../utils';
 
 export class ObjectHydrator extends Hydrator {
@@ -75,18 +75,21 @@ export class ObjectHydrator extends Hydrator {
     }
   }
 
-  private createCollectionItem<T extends AnyEntity<T>>(prop: EntityProperty, value: Primary<T> | EntityData<T>): T {
-    if (Utils.isPrimaryKey(value)) {
-      return this.factory.createReference(prop.type, value);
-    }
+  private createCollectionItem<T extends AnyEntity<T>>(prop: EntityProperty, value: Primary<T> | EntityData<T> | T): T {
+    const meta = this.em.getMetadata().get(prop.type);
+
+    if (Utils.isPrimaryKey(value, meta.compositePK)) {
+      const ref = this.factory.createReference<T>(prop.type, value);
+      this.em.merge(ref);
 
-    const child = this.factory.create(prop.type, value as EntityData<T>);
+      return ref;
+    }
 
-    if (wrap(child).__primaryKey) {
-      this.em.merge(child);
+    if (Utils.isEntity<T>(value)) {
+      return value;
     }
 
-    return child;
+    return this.factory.create(prop.type, value as EntityData<T>);
   }
 
 }

lib/typings.ts

@@ -94,7 +94,7 @@ export type MongoEntity<T extends { _id: IPrimaryKey; id: string }> = AnyEntity<
 export type EntityClass<T extends AnyEntity<T>> = Function & { prototype: T };
 export type EntityClassGroup<T extends AnyEntity<T>> = { entity: EntityClass<T>; schema: EntityMetadata<T> | EntitySchema<T> };
 export type EntityName<T extends AnyEntity<T>> = string | EntityClass<T>;
-export type EntityData<T extends AnyEntity<T>> = { [K in keyof T]?: T[K] | Primary<T[K]> | CollectionItem<T[K]>[] } & Dictionary;
+export type EntityData<T extends AnyEntity<T>> = { [K in keyof T]?: T[K] | Primary<T[K]> | EntityData<T[K]> | CollectionItem<T[K]>[] } & Dictionary;
 
 export interface EntityProperty<T extends AnyEntity<T> = any> {
   name: string & keyof T;

tests/EntityManager.mongo.test.ts

@@ -789,10 +789,10 @@ describe('EntityManagerMongo', () => {
     const cachedAuthor = orm.em.merge(Author, cache);
     expect(cachedAuthor).toBe(cachedAuthor.favouriteBook.author);
     expect(Object.keys(orm.em.getUnitOfWork().getIdentityMap())).toEqual([
-      'BookTag-' + tag1.id,
-      'BookTag-' + tag3.id,
       'Author-' + author.id,
       'Book-' + book1.id,
+      'BookTag-' + tag1.id,
+      'BookTag-' + tag3.id,
     ]);
     expect(author).not.toBe(cachedAuthor);
     expect(author.id).toBe(cachedAuthor.id);