Tag type discrimination POC

[stackoverfloweth]

Define kind to discriminate tags, require each kind is satisfied by setQueryData handler

Tags can be defined without kind, defaults to "default". Kind doesn't have to be unique. You can have 30 tags with "default" kind but as soon as you pass 2 tags with kind "default" in that have conflicting data types, your setQueryData is going to correctly provide and expect never.

const untypedTag = tag()
const stringTag = tag<string, 'name'>('name')
const numberTag = tag<number, 'count'>('count')

Note

This awkward syntax is a bit of a downside. Because of how TS works, we basically have to pass in the value twice, once in the generic and again at runtime. If this PR ends up being a good direction, we can talk through alt syntax that makes this less awkward

When you call setQueryData on a single tag it's a simple callback

setQueryData(numberTag, (data) => {
  expectTypeOf(data).toEqualTypeOf<number>()
  return 2
})

When you call setQueryData with multiple tags with the same kind or different kinds but same underlying data type, it's also a simple callback

const numberTag = tag<number, 'count'>('count')
const anotherNumberTag = tag<number, 'another'>('another')

setQueryData([numberTag, anotherNumberTag], (data) => {
  expectTypeOf(data).toEqualTypeOf<number>()
  return 2
})

// also ok
setQueryData([numberTag, anotherNumberTag], {
  count: (data) => {
    expectTypeOf(data).toEqualTypeOf<number>()
    return 2
  },
  another: (data) => {
    expectTypeOf(data).toEqualTypeOf<number>()
    return 42
  },
})

When you call setQueryData with multiple tags with different kinds, you MUST define a handler for each kind

setQueryData([numberTag, stringTag], {
  count: (data) => {
    expectTypeOf(data).toEqualTypeOf<number>()
    return data + 1
  },
  name: (data) => {
    expectTypeOf(data).toEqualTypeOf<string>()
    return data + 'bar'
  },
})