Allow enum to use a function

slukes commented 8 months ago

Is there an existing issue that is already proposing this?

[X] I have searched the existing issues

Is your feature request related to a problem? Please describe it

We are using some dynamic code to find all of the possible values of an enum i.e.

export function getPossibleValues(): string[] {
  return getMetadataArgsStorage()
    .tables.filter( // some condition here)
}

However since the enum option of @ApiProperty expects a static function and not a function, the result is dependent on the order of import of modules.

Describe the solution you'd like

Modification of enum property type to

    enum?: any[] | Record<string, any> | (() => any[] | Record<string, any>)

Teachability, documentation, adoption, migration strategy

Current users => 0 impact.

New users can use function for enum values if wished.

I suggest a docs change to:

To identify an enum, we must manually set the enum property on the @ApiProperty with an array of values or a function returning an array of values.

@ApiProperty({ enum: ['Admin', 'Moderator', 'User']})
role: UserRole;

@ApiProperty({ enum: () => getAvailableUserTypes() })
role: UserRole;

⚠️ Note that functions will only be called once when the API docs are generated, so you cannot add values dynamically after application startup.

What is the motivation / use case for changing the behavior?

We want to be able to add enum values by adding an decorator on some other nestjs component in our case a typeorm entity, we do not want to have to remember to update the possible enum values.