[F] getUnionAsEnum

function getUnionAsEnum(union): [undefined | UnionEnum, readonly Diagnostic[]]

Tries to convert a union into an enum. If the union only contains the same type of literal options with optionally the base scalar to mark extensibility we can represent this union as an enum of that type.

Parameters

Parameter	Type	Description
union	Union	Union to try to convert

Returns

[undefined | UnionEnum, readonly Diagnostic[]]

Example

Simple closed string enum

union PetKind { "cat", "dog" }

const [enum, diagnostics] = getUnionAsEnum(union);
enum.open === false
enum.open.members.get("cat") // { value: "cat", variant: ... }
enum.open.members.get("dog") // { value: "dog", variant: ... }

Simple open string enum

union PetKind { Cat: "cat", Dog: "dog", string }

const [enum, diagnostics] = getUnionAsEnum(union);
enum.open === true
enum.open.members.get("Cat") // { value: "cat", variant: ... }
enum.open.members.get("Dog") // { value: "dog", variant: ... }

Invalid case

union PetKind { Cat: "cat", Dog: 123, string }

const [enum, diagnostics] = getUnionAsEnum(union);
enum === undefined
diagnostics.length === 1