Duplicate entity names are not allowed - Mikro Orm - nestjs

Question

I created a migration for an entity in Mikro Orm. After that, i modified the entity and ran the migrations again. Now nestjs keeps giving me this error.
This was my entity.
#Entity()
export class Task extends BaseEntity<Task, 'id'> {
#PrimaryKey()
id: number;
#Property()
name: string;
#Property()
description: string;
}
I created initial migration with npx mikro-orm migration:create --initial. After that i modified my entity to this:
#Entity()
export class Task extends BaseEntity<Task, 'id'> {
#PrimaryKey()
id: number;
#Property()
name: string;
#Property()
description: string;
#Enum(() => TaskStatus)
status: TaskStatus = TaskStatus.OPEN;
}
export enum TaskStatus {
OPEN = 'OPEN',
IN_PROGRESS = 'IN_PROGRESS',
DONE = 'DONE',
}
After that, I ran two commands npx mikro-orm migration:create & npx mikro-orm migration:up.
Now NestJs keeps giving me this error.
[Nest] 13528 - 02/06/2021, 6:59:14 pm [NestFactory] Starting Nest application...
[Nest] 13528 - 02/06/2021, 6:59:14 pm [InstanceLoader] MikroOrmModule dependencies initialized +43ms
[Nest] 13528 - 02/06/2021, 6:59:14 pm [InstanceLoader] ConfigHostModule dependencies initialized +1ms
[Nest] 13528 - 02/06/2021, 6:59:14 pm [InstanceLoader] AppModule dependencies initialized +1ms
[Nest] 13528 - 02/06/2021, 6:59:14 pm [InstanceLoader] ConfigModule dependencies initialized +0ms
[Nest] 13528 - 02/06/2021, 6:59:14 pm [ExceptionHandler] Duplicate entity names are not allowed: Task +409ms
MetadataError: Duplicate entity names are not allowed: Task
at Function.duplicateEntityDiscovered (C:\dev\nodejs\nestjs\sandbox\node_modules\#mikro-orm\core\errors.js:151:16) at MetadataValidator.validateDiscovered (C:\dev\nodejs\nestjs\sandbox\node_modules\#mikro-orm\core\metadata\MetadataValidator.js:40:42)
at MetadataDiscovery.findEntities (C:\dev\nodejs\nestjs\sandbox\node_modules\#mikro-orm\core\metadata\MetadataDiscovery.js:81:24)
at processTicksAndRejections (node:internal/process/task_queues:93:5)
at async MetadataDiscovery.discover (C:\dev\nodejs\nestjs\sandbox\node_modules\#mikro-orm\core\metadata\MetadataDiscovery.js:34:9)
at async Function.init (C:\dev\nodejs\nestjs\sandbox\node_modules\#mikro-orm\core\MikroORM.js:42:24)
at async Injector.instantiateClass (C:\dev\nodejs\nestjs\sandbox\node_modules\#nestjs\core\injector\injector.js:290:37)
at async callback (C:\dev\nodejs\nestjs\sandbox\node_modules\#nestjs\core\injector\injector.js:42:30)
at async Injector.resolveConstructorParams (C:\dev\nodejs\nestjs\sandbox\node_modules\#nestjs\core\injector\injector.js:114:24)
at async Injector.loadInstance (C:\dev\nodejs\nestjs\sandbox\node_modules\#nestjs\core\injector\injector.js:46:9)

Answer 1

I also had this issue and I knew I didn't have a duplicate model name. The problem occurred after I had moved a model to a different directory.
The resolution was to clear the dist build folder and the temp metadata folders.

Answer 2

UPDATE
After investigation, the code can be run perfectly. There maybe some problems on the node_modules where some incomplete/incompatible packages exist.
The solution is to remove node_modules and reinstall again.
The steps you do is the following:
create a Task class
create migration file
modify the Task class
create migration file again
do the migration
If you modify the Task class without running migration command before, you will end up having 2 migration files with create task table command because mikro does not have any references of task table before any migration happened.
You can check the SQL in both migration files, it should be create table task xxx.
Therefore, there is a way to solve it:
delete the 2nd migration file first
run npx mikro-orm migration:up to create task table on DB without enum
run npx mikro-orm migration:create.
Right now, mikro has references of the task table and know that you want to alter table so the SQL in migration will be alter table task instead of create table
run npx mikro-orm migration:up to alter task table on DB with enum