Error when assigning a Date on a nullable property

[kalu06]

Describe the bug
I have some entity properties declared as follows:

@Property({ columnType: 'timestamp(3)', nullable: true })
createdAt: Date | null = null

I need this to be able to have null values from factories and be able to compare those with entities fetched from the database.

I get an error when trying to assign a date with orm.em.assign(foo, { createdAt: new Date() });, although foo.createdAt = new Date(); works.

(see below to reproduce with a full example)

Stack trace

ValidationError: Trying to set Foo.createdAt of type 'string' to 'Mon Oct 16 2023 13:58:46 GMT+0200 (Central European Summer Time)' of type 'date'
    at ValidationError.fromWrongPropertyType (/Users/lucascrivelli/Documents/Atipik/mikro-orm-test/node_modules/@mikro-orm/core/errors.js:22:16)
    at EntityValidator.validateProperty (/Users/lucascrivelli/Documents/Atipik/mikro-orm-test/node_modules/@mikro-orm/core/entity/EntityValidator.js:65:44)
    at EntityAssigner.assignProperty (/Users/lucascrivelli/Documents/Atipik/mikro-orm-test/node_modules/@mikro-orm/core/entity/EntityAssigner.js:77:49)
    at /Users/lucascrivelli/Documents/Atipik/mikro-orm-test/node_modules/@mikro-orm/core/entity/EntityAssigner.js:30:35
    at Array.forEach (<anonymous>)
    at EntityAssigner.assign (/Users/lucascrivelli/Documents/Atipik/mikro-orm-test/node_modules/@mikro-orm/core/entity/EntityAssigner.js:29:27)
    at SqlEntityManager.assign (/Users/lucascrivelli/Documents/Atipik/mikro-orm-test/node_modules/@mikro-orm/core/EntityManager.js:989:40)
    at /Users/lucascrivelli/Documents/Atipik/mikro-orm-test/dist/test.js:12:12
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
  entity: undefined
}

It seems that the type inferred from the EntityValidator is wrong (string instead of date).

To Reproduce
Steps to reproduce the behavior:

1. Create an entity with a property such as described above

import { Entity, PrimaryKey, Property } from "@mikro-orm/core";

@Entity()
export class Foo {
  @PrimaryKey()
  id!: number

  @Property()
  bar!: string

  @Property({ columnType: 'timestamp(3)', nullable: true })
  createdAt: Date | null = null
}

2. Try to orm.em.assign with a date like so:

const orm = await MikroORM.init(mikroOrmConfig);
const foo = orm.em.create(Foo, { bar: 'baz' });
orm.em.assign(foo, { createdAt: new Date() }); // doesn't work
// foo.createdAt = new Date(); // works
await orm.em.flush();
await orm.close();

Expected behavior
orm.em.assign to work the same as setting the property value directly.

Versions

Dependency	Version
node	18.6.0
typescript	5.2.2
mikro-orm	5.8.9
mikro-mysql	5.8.9

[B4nan]

The problem here is that you don't set the type, and since you use a union type, that cannot be inferred via reflect-metadata, so the ORM thinks the property is actually a string.

You can do this instead:

@Property({ type: 'date', columnType: 'timestamp(3)', nullable: true })
createdAt: Date | null = null

[kalu06]

Would be great to infer this one automatically as well as it's kind of tricky to know we need to specify type for this use case, but I'm not sure it's that important. What do you think?

[B4nan]

Yeah it's indeed best if things just work :] I was looking at the code and we already do this for bigints and JSON props, it's just about adding 3 lines somewhere in this method:

https://github.com/mikro-orm/mikro-orm/blob/master/packages/core/src/metadata/MetadataDiscovery.ts#L992

[tobiaskraus]

I had the same issue, and the type: "date" solution worked for me. But wanted to mention, that it only crashed while updating from @5.4.2 to @5.8.8. Somehow it wasn't an issue in older mikro-orm version.

[B4nan]

This will do it 6bc116a?w=1

[B4nan]

and the type: "date" solution worked for me

FYI in v6 type: 'date' means date, not datetime, so if you want to be future proof, use type: 'datetime' or type: 'Date' (as Date is how it would be normally inferred.

(https://github.com/mikro-orm/mikro-orm/blob/v6/docs/docs/upgrading-v5-to-v6.md#changes-in-date-property-mapping)