Suggestion: require value property to avoid collisions when nesting

When a union is nested inside a union, without a value property specified, the two values will collide:

E.g.

https://stackblitz.com/edit/typescript-ef4lbo?file=index.ts

import { unionize, ofType } from 'unionize';

const InsideFoo = unionize({
  Bar: ofType<{ bar: number }>(),
});
type InsideFoo = typeof InsideFoo._Union;
const A = unionize({
  Foo: ofType<InsideFoo>(),
});

const a = A.Foo(InsideFoo.Bar({ bar: 1 }));

console.log(JSON.stringify(a))

Logs:

{"bar":1,"tag":"Foo"}

As you can see, the tag for the nested union is lost, and the value for the nested union is merged with the value for the parent union.

We can fix this by specifying a value property:

import { unionize, ofType } from 'unionize';

const InsideFoo = unionize({
  Bar: ofType<{ bar: number }>(),
}, { value: 'value' });
type InsideFoo = typeof InsideFoo._Union;
const A = unionize({
  Foo: ofType<InsideFoo>(),
}, { value: 'value' });

const a = A.Foo(InsideFoo.Bar({ bar: 1 }));

console.log(JSON.stringify(a))

Logs:

{"tag":"Foo","value":{"tag":"Bar","value":{"bar":1}}}

For this reason, I think that the value property should be required. I always forget to add one, and then run into these issues. Ideally I wouldn’t have to specify a value property each time I use unionize.

Related code: https://github.com/pelotom/unionize/blob/f6ebfa50177aa3fdb724378c158e400c72d0d625/src/index.ts#L115

[OliverJAsh]

You’re right. Amazing! Nice one @karol-majewski

[pelotom]

@OliverJAsh this no longer type checks since #56:

const InsideFoo = unionize({
  Bar: ofType<{ bar: number }>(),
});
type InsideFoo = typeof InsideFoo._Union;
const A = unionize({
  Foo: ofType<InsideFoo>(),
});

You are forced to specify either a) a tag prop other than "tag" for InsideFoo or b) a value prop for A.