feat(schema): allow using a POJO for enum to support TypeScript enums

[AbdelrahmanHafez]

fixes #9546 #9535

[vkarpov15]

Great work, we'll release this with v5.11 👍

[AbdelrahmanHafez]

Thank you, that works. 👍

[joergbaier]

@AbdelrahmanHafez @vkarpov15 My team began updating our enum values to typescript enums. However there is not a way to allow null in this case. This is somewhat related to the discussion here #3044

enum Color {
  Red = "red",
  Blue = "blue",
  ...
}

const SomeSchema = new Schema({
  color: { type: String, enum: Color },
  ...
});

As far as I can tell, there is no way to allow the color field to be nullable with this syntax. Typescript doesn't allow null in the enum and there is not an option to allow it in mongoose. We would need to use the previous syntax in this case (converting the enum to an array and concatenating null).

It looks like typegoose added a addNullToEnum option to handle this.
typegoose/typegoose#235

Any thoughts on exposing a nullable option? I imagine that allowing null with required: false would not make sense.

[vkarpov15]

@joergbaier the syntax you put would allow color to be null. The issue you posted says the following:

"Mongoose requires to add null to the enum array to allow an empty value to be used, even when required is false."

That statement is incorrect. You don't need to add null to the enum.