[typescript] Add additional Types for possible null values

[sschneider-ihre-pvs]

Is your feature request related to a problem? Please describe.

So there is the Maybe type already which says the value can be null which actually is more like Nullable if you ask me. Anyway, so the value may be null but if it is optional it also does not need to exist at all, so you either have ? or | undefined added to the Maybe which could be shorter with adding an extra type for that.

Describe the solution you'd like
So additionally to the Maybe utility type lets have something like Nullable (😁 ) which is something like type Nullable<T> = Maybe<T> | undefined = T | null | undefined
Or if you want some other intermediate type maybe something like

type Nothing = null | undefined
type Nullable<T> = T | Nothing

Additional context
Let's have a look at validation lib Zod for a moment. You have the option to use .nullable() and chain .optional() as well, but there is a short form for this which is called .nullish()

[JustFly1984]

@sschneider-ihre-pvs It is not only Maybe or Nullable. Every optional value should have | undefined added, to satisfy typescript tsconfig flag exactOptionalPropertyTypes: true. For example: __typename?: 'TypeName' | undefined

Extending Maybe with codegen.yml typescript-operations config maybeValue is not enough.

PS: I've created similar issue #7448

[sschneider-ihre-pvs]

__typename?: 'TypeName' | undefined isn't that a tautology?

[JustFly1984]

@sschneider-ihre-pvs This is my current headache with typescript 4 exactOptionalPropertyTypes: true

There is a subtle difference with optional and undefined.
When this flag is turned on, Optional does not expect the prop on provided props object, while undefined expects the prop on the object to have undefined value.

Basically if there is a prop with undefined value on the object, it could be iterated by Object.keys, but if the prop is optional, it is not defined on the object, so would not end up in Object.keys output.

In React it helps to prevent unexpected props to fall through JSX into DOM nodes attributes in specific cases

interface PropsA {
  a: string
  b?: string
}
interface PropsB {
  a: string
  b?: string | undefined
}

function ComponentA({ a, b }: PropsA): { return null }
function ComponentB({ a, b }: PropsB): { return null }

// Error!!! with exactOptionalPropertyTypes enabled
<ComponentA a="a" b={undefined} />

<ComponentA a="a" />

// NO ERROR with exactOptionalPropertyTypes enabled
<ComponentB a="a" b={undefined} />

<ComponentB a="a" />

[sschneider-ihre-pvs]

Ah the key, value conundrum. Is the key optional or the value.

[sschneider-ihre-pvs]

Always remember, graphql does not follow that concept, it only knows nullable and non-nullable.

[JustFly1984]

But typescript does - and generated values are optional.

[JustFly1984]

btw, I've regenerated types for one project, and I see a lot of optional properties on mutation types, hooks arguments, etc.
I have to change manually the copy of generated code.

[JustFly1984]

Do I understand correctly, it does not use tsconfig for generating types?

[JustFly1984]

@sschneider-ihre-pvs can you please clarify if it is possible to implement in near future?

[sschneider-ihre-pvs]

@JustFly1984 I do not know. there was no response yet

[hinogi]

Well I guess I just ran in this problem again :D