enchance `leavesOnly: true` for nullable fields (need append option for Paths util type)

[salisbury-espinosa]

currrent behavior:

type TestType = {
  test?: null | { someField: number };
};

// PathsFromTestType = 'test' | 'test.someField'
type PathsFromTestType = Paths<
  TestType,
  { leavesOnly: true; maxRecursionDepth: 10 }
>;

expected behavior:
// PathsFromTestType = 'test.someField'

workaroround

type TestType = {
  test?: null | { someField: number };
};

// PathsFromTestType = 'test. someField'
type PathsFromTestType = Paths<
  SetNonNullableDeep<
    TestType,
    Paths<TestType, { leavesOnly: true; maxRecursionDepth: 10 }>
  >,
  { leavesOnly: true; maxRecursionDepth: 10 }
>;

[som-sm]

@salisbury-espinosa Do you mean we should add an option like dontTreatNullAsLeaf? If so, it feels like a one-off use case, and I think it's okay to first remove nulls and then retrieve the leaves as you've already mentioned. Although, it'd be cleaner once we have the NonNullableDeep type that removes nulls from all paths.

[som-sm]

However, it might make sense to add an option like exclude, which would exclude paths that yield the specified type. For example:

type T1 = Paths<{a: {b: string; c: number}; d: string}, {exclude: string}>
//   ^? type T = "a" | "a.c"

type T2 = Paths<{a: {b: string; c: number}; d: string}, {exclude: string, leavesOnly: true}>
//   ^? type T = "a.c"

[salisbury-espinosa]

However, it might make sense to add an option like exclude, which would exclude paths that yield the specified type. For example:

type T1 = Paths<{a: {b: string; c: number}; d: string}, {exclude: string}>
// ^? type T = "a" | "a.c"

type T2 = Paths<{a: {b: string; c: number}; d: string}, {exclude: string, leavesOnly: true}>
// ^? type T = "a.c"

exclude - good, but what about removing optional ones?

#1303 (comment)

[som-sm]

Just looked over the different points mentioned in #1303, and these seem like separate problems and not something that should be handled within Paths.

For example:

1. Remove nulls before instantiating Paths.
2. Remove optionals before instantiating Paths.
3. Remove arrays/tuples before instantiating Paths.

[salisbury-espinosa]

Remove nulls before instantiating Paths.

Well, that's what I do now using SetNonNullableDeep in the example above or here.
But it would probably be more convenient if the utility Paths itself accepted this as an option...