routing-controllers: fix: Enum in @QueryParams and @QueryParam: Value cannot be parsed into JSON

Some code to reproduce issue:

enum LabelType {
  Sent = 'Sent',
  Inbox = 'Inbox'
}

class Query {
  @IsEnum(LabelType)
  label: LabelType;
}

@JsonController()
export class ThreadController {
  @Get('/threads')
  async list(
    @QueryParams() query: Query
  ) {
    return "ok";
  }
  @Get('/threads/one')
  async list(
    @QueryParam('label') label: LabelType,
  ) {
    return "ok";
  }

  @Post('/threads')
  async postList(
    @Body() query: Query
  ) {
    return "ok";
  }
}

Issue:

Post method is working as expected, but Get fails with this error: Http error: Given parameter label is invalid. Value ("Sent") cannot be parsed into JSON.

Possible reason:

Typescript emits “Object” for “design:type” when type is inferred original issue. In that case string enum treats as an object and routing-controllers tries to parse string. That happens in normalizeParamValue method of ActionParameterHandler here. normalizeParamValue isn’t handles params from @Body, that’s why Post works as expected.

Workaround:

Until it fixed we can explicitly specify enum type. Not sure if that will not break anything else, but working fine for me:

export class Query {
  @Reflect.metadata('design:type', { name: 'string' })
  @IsEnum(LabelType)
  label: LabelType;
}

For @QueryParam it’s possible to set parameter’s type:

@QueryParam('label', { type: 'string' }) label: LabelType