invalid serialization of json during upsert

[boredland]

Describe the bug

we discovered that during upsert a json property is being serialized into a string. this test demonstrates that behaviour.

To Reproduce
Steps to reproduce the behavior:

#3786

Versions

Dependency	Version
node	16.18.0
typescript	4.9.3
mikro-orm	5.5.3

we were able to reproduce this with sqlite, better-sqlite and postgres drivers (didn't test others).

[darioielardi]

Unfortunately, we are still seeing this with v5.6.0.

[B4nan]

Then please provide a complete repro, the fix included a passing test case 🤷

[Zmaon]

I just reproduced the same issue with upsertMany using Mikro-orm 5.6.9.
For me it happens on any JSON column when the type is set like this in the entity:

@Property({ type: 'json' })

If settings:

@Property({ columnType: 'json' })

then the problem is gone.

[B4nan]

Then provide the repro please, both should behave exactly the same since 5.6.9, before the type: 'json' is what you actually need, as that is what automatically uses the JsonType - and that is what you need to have correct JSON property handling.

[Zmaon]

Ok I wrote a simple test that does nothing but create two tables and insert data into them. For some reason I wasn't able to just set columnType='json' in MyEntity2, I had to also add type='json' which is not the case in my other projects. The behaviour is the same anyway. I hope this helps.

package.json:

{
  "devDependencies": {
    "@babel/plugin-proposal-decorators": "^7.20.13",
    "@types/jest": "^29.4.0",
    "jest": "^29.4.3",
    "ts-jest": "^29.0.5",
    "typescript": "^4.9.5"
  },
  "dependencies": {
    "@mikro-orm/core": "^5.6.9",
    "@mikro-orm/mysql": "^5.6.9"
  }
}

mo.test.ts

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

@Entity()
class MyEntity1 {
  @PrimaryKey({ type: 'number' })
  id!: number;

  @Property({ type: 'json' })
  field!: object;
}

@Entity()
class MyEntity2 {
  @PrimaryKey({ type: 'number' })
  id!: number;

  @Property({ type: 'json', columnType: 'json' })
  field!: object;
}

test('mikro-orm JSON serialization with upsertMany', async() => {
  const orm = await MikroORM.init({
    type: 'mysql',
    dbName: 'motest',
    host: '127.0.0.1',
    user: 'root',
    password: 'root',
    port: 3378,
    allowGlobalContext: true,
    entities: [MyEntity1, MyEntity2]
  });
  await orm.schema.refreshDatabase();
  const em = orm.em;

  const entity1 = em.create(MyEntity1, {
    id: 1,
    field: {
      firstName: 'John',
      lastName: 'Doe'
    }
  });
  em.upsertMany([entity1]);
  const entity2 = em.create(MyEntity2, {
    id: 1,
    field: {
      firstName: 'Albert',
      lastName: 'Doe'
    }
  });
  em.upsertMany([entity2]);
});

Looking into the database I see that for my_entity1:

and for my_entity2: