Extending BaseEntity causes underlying methods to return types of BaseEntity instead of their higher order types.

[chevsunpower]

Issue Description

If I create a class and extend BaseEntity I get the active record style of interaction as expected. However the methods on the base class only return type BaseEntity. For example, here's a simple active record entity:

class Project extends BaseEntity {

  @PrimaryGeneratedColumn("uuid")
  id: string;
  
  @Column({ nullable: true })
  comment: string;

}

Now if I save a new entity it will save it as expected:

await Project.save({ comment: "hello, typeorm" });

However, if I then try to get the returned entity and read it's ID it will complain:

const newProject = await Project.create({ comment: "hello, typeorm" });
console.log(newProject.id); // does not work

Here we get Property 'id' does not exist on type 'BaseEntity'. I have to manually cast the generic save method to rectify this, which kind of defeats the point of active record simplicity a little bit.

const newProject = await Project.create<Project>({ comment: "hello, typeorm" });
console.log(newProject.id); // this works

Expected Behavior

I would expect the save method in this case to return an instance of Project.

My Environment

Dependency	Version
Operating System
Node.js version	16.14.2
Typescript version	4.7.4
TypeORM version	0.3.7

Relevant Database Driver(s)

DB Type	Reproducible
aurora-mysql	no
aurora-postgres	no
better-sqlite3	no
cockroachdb	no
cordova	no
expo	no
mongodb	no
mysql	no
nativescript	no
oracle	no
postgres	yes
react-native	no
sap	no
spanner	no
sqlite	no
sqlite-abstract	no
sqljs	no
sqlserver	no

Are you willing to resolve this issue by submitting a Pull Request?

• ✖️ Yes, I have the time, and I know how to start.
• ✖️ Yes, I have the time, but I don't know how to start. I would need guidance.
• ✖️ No, I don’t have the time, but I can support (using donations) development.
• ✅ No, I don’t have the time and I’m okay to wait for the community / maintainers to resolve this issue.

[chevsunpower]

Maybe it's not easy to get the type from static class methods without a manually specified generic but at the very least I'd love to be able to specify the type on the class itself.

class Project extends BaseEntity<Project> {
  /* ... */
}

At least then we'd only have to specify it once instead of every time you use a static method on the class.

[lucas-labs]

I'm getting the same error.

It's returning the wrong type, it should return the entity's class.

Maybe it's not easy to get the type from static class methods without a manually specified generic but at the very least I'd love to be able to specify the type on the class itself.

I'm pretty sure It was working ok in version 0.2.x, the code in the screenshot above wasn't showing any errors at least.

This is how it was defined back in 0.2:

typeorm/src/repository/BaseEntity.ts

Lines 156 to 158 in 90a8deb

	static create<T extends BaseEntity>(this: ObjectType<T>, entityOrEntities?: any): T {
	return (this as any).getRepository().create(entityOrEntities);
	}

Now it has been changed:

typeorm/src/repository/BaseEntity.ts

Lines 185 to 190 in bb33cd0

	static create<T extends BaseEntity>(
	this: { new (): T } & typeof BaseEntity,
	entityOrEntities?: any,
	) {
	return this.getRepository<T>().create(entityOrEntities)
	}

[olivierlacan]

This is a bit of a bummer because we were hoping to use await SomeEntity.create(entityProperties).save() directly in test setup logic but we're having to fall back to this instead to get proper typings:

const instance = new SomeEntity(entityProperties);
await instance.save()
// => Promise<SomeEntity>

Whereas this sadly doesn't work:

await SomeEntity.create(entityProperties).save();
// => Promise<BaseEntity>

@AlexMesser it looks like this typing regression was introduced by this bug fix, any chance you could give it a look?

It looks like the type union added here is blocking the BaseEntity descendant from showing up as the return type.