Four findings, all valid:
1. Returning `T` was unsound. The collapse genuinely changes two fields —
`type` stops being an array, `anyOf` becomes `undefined` — so a caller
whose `T` typed either that way could keep treating it so afterwards.
The result is now `T | NormalizedNullableUnion<T>`, which states exactly
that: `Omit<T, "type" | "anyOf">` plus a `RenderableType` `type`, a
cleared `anyOf`, and `nullable`. The one assertion left is isolated in a
`collapsed()` helper, needed only because `Omit` stays deferred while `T`
is open.
2. A typeless `enum` does not imply strings. JSON Schema allows
`enum: [1, 2]`, and inferring `"string"` for it would hand numbers to a
`Select` declared `string[]`, and make the TUI submit `"1"` for `1`. Now
only an all-string enum earns the inference; anything else stays on the
JSON fallback. An explicit `type` is still authoritative.
3. `hasMissingRequiredFields` counted every null as missing, so clearing a
*required* nullable enum — newly possible via the clear button — would
disable submit on a value the schema permits. `required` constrains
presence, not content, so null now counts as present exactly when the
field's schema admits it.
4. `collectSchemaDefaults` read the raw union, so a default nested inside a
nullable object's branch was displayed by the form but never seeded into
the submitted values. It normalizes each property first, like the
renderer does.
Signed-off-by: cliffhall <cliff@futurescale.com>
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