Remove functions from enum values

[SimonRosenau]

Description

This change removes function declarations from enum values.

I am using an enum with an companion namespace with utility functions:

export enum ResponseTypeEnum {
  Code = 'code',
}

export namespace ResponseTypeEnum {
  export const fromString = (value: string): ResponseTypeEnum => {
    switch (value.toLowerCase()) {
      case 'code':
        return ResponseTypeEnum.Code
      default:
        throw Error('Invalid response type: ' + value)
    }
  }
}

Within a request body as such:

export class Request {
  @IsEnum(ResponseTypeEnum)
  responseType: ResponseTypeEnum
}

The error returned by the server upon sending an invalid enum value is serialized as the following:

"responseType must be one of the following values: code, (value) => {\n        switch (value.toLowerCase()) {\n            case 'code':\n                return ResponseTypeEnum.Code;\n            default:\n                throw Error('Invalid response type: ' + value);\n        }\n    }"

This PR removes the function declaration from the possible enum values in the error message

Checklist

• the pull request title describes what this PR does (not a vague title like Update index.md)
• the pull request targets the default branch of the repository (develop)
• the code follows the established code style of the repository
  • npm run prettier:check passes
  • npm run lint:check passes
• tests are added for the changes I made (if any source code was modified)
• documentation added or updated
• I have run the project locally and verified that there are no errors

Fixes

[Clashsoft]

Why not combine the filter operations to save an intermediate array creation?

[SimonRosenau]

@Clashsoft In this case I would prefer code style in favor of performance, as honestly the performance gain would be quite minuscule, but if others would agree that this should be refactored I would also be open to do so

[Clashsoft]

In addition I would even argue that the parseInt should be guarded with typeof value === 'string' instead of !== function because that is the assumption of as string in the last line. So some change is necessary anyway

[SimonRosenau]

Hey @Clashsoft! Sorry for the long wait. I have addressed your requested changes, but now I'm not even sure whether the isNaN(parseInt(key)) check is even needed anymore?

[Clashsoft]

@SimonRosenau Thanks for addressing! I believe you don't need it anymore. See https://stackoverflow.com/a/43091709/4138801

Object.keys(myEnum).map(key => myEnum[key]).filter(value => typeof value === 'string') as string[];

Or with ES2017 according to this comment:

Object.values(myEnum).filter(value => typeof value === 'string') as string[];

[SimonRosenau]

@Clashsoft Makes absolute sense! Adjusted 🙂

[Clashsoft]

LGTM!