fix(postgres,mysql): better support for enum and enum array

[vlapo]

• better support all types of typescript enums (numeric, string, heterogeneous) + tests + docs - Fix Enum: migration generation problem #3393, Fix Entity properties which are Enums represented by number are returned as string #3072

export enum NumericEnum {
    ADMIN,
    EDITOR,
    MODERATOR,
    GHOST
}

export enum StringEnum {
    ADMIN = "a",
    EDITOR = "e",
    MODERATOR = "m",
    GHOST = "g"
}

export enum HeterogeneousEnum {
    NO = 0,
    YES = "YES",
}

• default values for enum array coluns (postgres) could be now defined as array - Fix Column for Array[Enum] gives Postgres & TypeOrm an error #3323

@Column({
    type: "enum",
    enum: StringEnum,
    array: true,
    default: [StringEnum.ADMIN]
})
stringEnums: StringEnum[];

• add enum type to sample - Fix Enum sample #3392

[pleerock]

what if value was defined as "1" and user expects numbers?

[pleerock]

I don't think we'll be able to make "heterogeneous" way possible to work. The only option I see is to support string-only or number-only. If enum was defined in a "heterogeneous" way - we either throw error either enforce strings.

(to understand if its string or numeric based we do Object.keys(enum).every(key => typeof enum[key] === "number"))

[vlapo]

Yeah I decided to force all string numbers to classic javascript numbers, so values of this enum will be transformed to number after select from databases:

enum TestEnum {
    NO = "0",
    YES = "1"
}

But in line you are highlighted we can check if exists numeric enum value (Object.keys(enum).some(key => enum[key] === parseInt(value))) and convert it only if exists. After that change the only one edge case will be enum like this:

enum TestEnum {
    YES1 = 1
    YES = "1"
}

And this looks like really edge case.

[pleerock]

Right, last case is really edge case and I think its okay if we don't cover it. But first case should work properly (convert "0" to string, not number).

[vlapo]

Updated src and added test enum with numeric values as string.

[pleerock]

This PR is amazing 🎆

[pleerock]

much more cleaver than what I have suggested!

[pleerock]

Awesome!