Apollo-tooling: apollo client:codegen Option for different TypeScript enum output

[rautenrieth-da]

Currently, the following GraphQL type

enum Color {
  RED
  BLUE
}

generates the following TypeScript type

export enum Color {
  RED = "RED",
  BLUE = "BLUE",
}

I would like to have the option to generate the following type instead:

export type Color = "RED" | "BLUE";

This definition provides the same safety, but is more efficient and works better with TypeScript structural typing.

Unrelated: consider generating const enum instead of enum.

[mike-marcacci]

Related:

• #193 - [TS] Use Typescript string enum for enums
• #247 - Use TypeScript string enums

[slorber]

+1, having an enum is annoying for me. I don't want to import the enum and to Enum.Value, I just want to use string literals, it's as safe as enums and works nicely

[RyanCavanaugh]

247 was a mistake IMO. String enums should only really be used when you want the underlying string value to be opaque, and that isn't a feature that GraphQL can provide. This would maybe be a good idea if you could produce stable key names, but the key names are going to change just as often as the string values themselves, so there's no point.

[Jessidhia]

String enums still have a slight advantage in that you can find all usages of it. String constants actually can be searched by "find all usages", which was a nice surprise (:tada:), but typescript can't distinguish "intentional" uses from "coincidental" uses of a given string constant -- the string enums work to disambiguate them, especially if there are multiple different enums in your schema that happen to partially overlap in some of the values; it would be good to know _which_ enum is being referred to when the value appears in code.

I think this might be mitigated by the planned "unique types" feature, but I haven't seen if it can be made to work for this use case.

[rohit-gohri]

export type Color = "RED" | "BLUE";

These also work better if you have a js codebase and are using checkjs, there is no way (AFAIK) to import and use the typescript enum.

[grantila]

I've fixed this in #1750 🙄