"invalid input syntax for type json" when trying to store an array of objects in PG jsonb column

[bill-o-more]

Describe the bug
I'm trying to store an array of objects inside a jsonb column in Postgres.
My model is defined like this:

type GeoItem = {
    kind: 'borough' | 'city' | 'county' | 'etc';
    name: string
}
export class ServicePerson {
    @PrimaryKey({ columnType: 'uuid', defaultRaw: `uuid_generate_v4()` })
    id = uuidv4();

    @Property({ columnType: 'jsonb', default: [] })
    serviceArea: GeoItem[] = [];
}

When I run

const servicePerson = orm.em.create(ServicePerson, { serviceArea: [{kind: 'city', name: 'Mordor'}, {kind: 'city', name: 'Gotham'}] });
orm.em.persistAndFlush(servicePerson);

I get the following error:

"insert into \"service_person\" (\"id\", \"service_area\") values ('21a101b6-cae5-4094-bbf7-5a19eef37d7f', '{[object Object],[object Object]}') returning \"id\", \"service_area\" - invalid input syntax for type json"

No TS warnings whatsoever, if I make a breakpoint just before flushing and inspect theservicePerson entity I see the correct array with correct objects.

Stack trace

{"type":"DriverException","message":"insert into "service_person" ("id", "service_area") values ('21a101b6-cae5-4094-bbf7-5a19eef37d7f', '{[object Object],[object Object]}') returning "id", "service_area" - invalid input syntax for type json" - invalid input syntax for type json","stack":"DriverException: insert into "service_person" ("id", "service_area") values ('21a101b6-cae5-4094-bbf7-5a19eef37d7f', '{[object Object],[object Object]}') returning "id", "service_area - invalid input syntax for type json
    at PostgreSqlExceptionConverter.convertException (/path/to/my/project/node_modules/@mikro-orm/core/platforms/ExceptionConverter.js:8:16)
    at PostgreSqlExceptionConverter.convertException (/path/to/my/project/node_modules/@mikro-orm/postgresql/PostgreSqlExceptionConverter.js:42:22)
    at PostgreSqlDriver.convertException (/path/to/my/project/node_modules/@mikro-orm/core/drivers/DatabaseDriver.js:197:54)
    at /path/to/my/project/node_modules/@mikro-orm/core/drivers/DatabaseDriver.js:201:24
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async PostgreSqlDriver.nativeInsertMany (/path/to/my/project/node_modules/@mikro-orm/knex/AbstractSqlDriver.js:303:21)
    at async ChangeSetPersister.persistNewEntity (/path/to/my/project/node_modules/@mikro-orm/core/unit-of-work/ChangeSetPersister.js:85:21)
    at async ChangeSetPersister.executeInserts (/path/to/my/project/node_modules/@mikro-orm/core/unit-of-work/ChangeSetPersister.js:29:13)
    at async ChangeSetPersister.runForEachSchema (/path/to/my/project/node_modules/@mikro-orm/core/unit-of-work/ChangeSetPersister.js:68:13)
    at async UnitOfWork.commitCreateChangeSets (/path/to/my/project/node_modules/@mikro-orm/core/unit-of-work/UnitOfWork.js:739:9)

Expected behavior
I'd expect this array to be saved into the DB with no errors

Additional context
I'm a noob. Please point me into the relevant doc if I missed one - seen this, but couldn't find the answer there

Versions

Dependency	Version
node	18.12.1
typescript	5.0.4
mikro-orm	5.7.12
your-driver	Postgres

[B4nan]

Looks like the detection of JSON types based on columnType is not working properly.

You should be doing this instead, as JSONb is the default mapping for JSON columns in postgres, no need to specify that via columnType. By using type you will also set the JsonType to that property which handles the conversion.

@Property({ type: 'json', default: '[]' })
serviceArea: GeoItem[] = [];

edit: I see, the problem is that this is array mapping, and the mapped type is first inferred as ArrayType instead, should be easy to fix