Cannot read properties of undefined (reading 'toLowerCase') (NextJS 11)

[Arslanoov]

Hello. Thank you for the library

Describe the bug
When I am trying to initialize orm, this error appears

Stack trace

[discovery] ORM entity discovery started, using ReflectMetadataProvider
[discovery] - processing entity User
error - TypeError: Cannot read properties of undefined (reading 'toLowerCase')
at ReflectMetadataProvider.initPropertyType (/usr/src/app/node_modules/@mikro-orm/core/metadata/ReflectMetadataProvider.js:17:83)
    at /usr/src/app/node_modules/@mikro-orm/core/metadata/ReflectMetadataProvider.js:9:54
    at ReflectMetadataProvider.initProperties (/usr/src/app/node_modules/@mikro-orm/core/metadata/MetadataProvider.js:26:23)
    at async ReflectMetadataProvider.loadEntityMetadata (/usr/src/app/node_modules/@mikro-orm/core/metadata/ReflectMetadataProvider.js:9:9)
    at async MetadataDiscovery.discoverEntity (/usr/src/app/node_modules/@mikro-orm/core/metadata/MetadataDiscovery.js:182:13)
    at async MetadataDiscovery.discoverReferences (/usr/src/app/node_modules/@mikro-orm/core/metadata/MetadataDiscovery.js:131:13)
    at async MetadataDiscovery.findEntities (/usr/src/app/node_modules/@mikro-orm/core/metadata/MetadataDiscovery.js:71:9)
    at async MetadataDiscovery.discover (/usr/src/app/node_modules/@mikro-orm/core/metadata/MetadataDiscovery.js:34:9)
    at async Function.init (/usr/src/app/node_modules/@mikro-orm/core/MikroORM.js:42:24)
    at async handler (webpack-internal:///./src/api/useCases/articles/getAll/handler.ts:20:7) {
  page: '/articles'
}

To Reproduce
Steps to reproduce the behavior:

1. Clone this repository https://github.com/Arslanoov/red
2. run make build
3. run make up
4. run make migrate
5. Try to open localhost:3000/articles page

Expected behavior
Page should open

Additional context
Api files: https://github.com/Arslanoov/red/tree/main/app/src/api
Models folder: https://github.com/Arslanoov/red/tree/main/app/src/api/model
ORM config: https://github.com/Arslanoov/red/blob/main/app/src/api/config/mikroOrm.ts
Database init: https://github.com/Arslanoov/red/blob/main/app/src/api/utils/database/init.ts

Versions

Dependency	Version
node	16
typescript	4.4.4
mikro-orm	4.5.9
next	11.1.2
reflect-metadata	0.1.13

[Arslanoov]

I fixed this issue by adding type: 'string' to all enum properties
It's strange, because documentation doesn't mention it
I think I should close this issue

[msheakoski]

Thank you @Arslanoov! I lost many hours trying to figure out if it was a TypeScript or SWC or Babel decorators issue, or something automatic that Next.js was doing. It was working without Next.js but when loading in an API route the "toLowerCase" error started happening.

What worked for me was EnumType:

import { Enum, EnumType } from "@mikro-orm/core"

@Enum({ type: EnumType, items: () => CountryCode })
country!: CountryCode

[superiums]

same issue.
this is caused by the metaDataDiscovery.js

 getMappedType(prop) {
        this.logger.log('discovery-->',JSON.stringify(prop))
        let t = prop.columnTypes?.[0] ?? prop.type.toLowerCase();
      
...
}

after debug, i found there's no type prop for Enum properties.
so i have to add a type ( tinnyint /smallint/string is ok) for all enum properties. but it would be better to add a default type for it by mikroorm.

this works:

  @Enum({ type: 'tinyint', items: () => ORG_SCOPE, nullable: true })
  orgScope: ORG_SCOPE;