feat(core): add disableContextResolution option to em.fork()

Use this flag to ignore current async context - this is required if we want
to call `em.fork()` inside the `getContext` handler.

Closes #3338

packages/core/src/EntityManager.ts

@@ -881,7 +881,7 @@ export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
    * Returns new EntityManager instance with its own identity map
    */
   fork(options: ForkOptions = {}): D[typeof EntityManagerType] {
-    const em = this.getContext(false);
+    const em = options.disableContextResolution ? this : this.getContext(false);
     options.clear ??= true;
     options.useContext ??= false;
     options.freshEventManager ??= false;
@@ -1197,5 +1197,7 @@ export interface ForkOptions {
   useContext?: boolean;
   /** do we want to use fresh EventManager instance? defaults to false (global instance) */
   freshEventManager?: boolean;
+  /** use this flag to ignore current async context - this is required if we want to call `em.fork()` inside the `getContext` handler */
+  disableContextResolution?: boolean;
   flushMode?: FlushMode;
 }

tests/EntityManager.mongo.test.ts

@@ -438,9 +438,16 @@ describe('EntityManagerMongo', () => {
     expect(fork.getMetadata()).toBe(orm.em.getMetadata());
     expect(fork.getUnitOfWork().getIdentityMap()).toEqual(new IdentityMap());
 
-    // request context is not started so we can use UoW and EF getters
+    // request context is not started, so we can use UoW and EF getters
     expect(fork.getUnitOfWork().getIdentityMap()).not.toBe(orm.em.getUnitOfWork().getIdentityMap());
     expect(fork.getEntityFactory()).not.toBe(orm.em.getEntityFactory());
+
+    const spy = jest.spyOn(EntityManager.prototype, 'getContext');
+    const fork2 = orm.em.fork({ disableContextResolution: true });
+    expect(spy).toBeCalledTimes(2);
+
+    const fork3 = orm.em.fork({ disableContextResolution: false });
+    expect(spy).toBeCalledTimes(5);
   });
 
   test('findOne with empty where will throw', async () => {