Files
react-native/scripts
Zeya PengandAlex Hunt 9a7b821a02 Fix TS exactOptionalPropertyTypes compatibility for generated types (#57628) (#57699)
Summary:
Pull Request resolved: https://github.com/react/react-native/pull/57628

NOTE: Patches over a `flow-api-translator` bug, which I'll fix upstream later. We need to pick this to `0.87-stable` to resolve user integration issues.

**Context**

TypeScript's `exactOptionalPropertyTypes` flag (strict mode) creates a distinction between `foo?: T` and `foo?: T | undefined`.

```js
// Flow's semantics

interface Props {
  onRefresh?: () => void;
}
const a: Props = { onRefresh: undefined }; // ✅ ok
```
```ts
// TypeScript with exactOptionalPropertyTypes: true (i.e. strict mode)

interface Props {
  onRefresh?: () => void;
}
const a: Props = { onRefresh: undefined }; // ❌ error

interface PropsFixed {
  onRefresh?: (() => void) | undefined;
}
const b: PropsFixed = { onRefresh: undefined }; // ✅ ok
```

With this added strictness in TypeScript, our generated types via `flow-api-translator` could create downstream type incompatibility in apps.

**This diff**

Patches the above issue in React Native's Flow → TS `types_generated/` pipeline. We transform all instances to the wider `foo?: T | undefined` format, for maximum compatibility.

**Notes**

`foo?: T [| undefined]` **remains stripped** in the API snapshot (existing transform with the aim of a concise format). There is a net, nonfunctional snapshot diff around function members, which (as a positive result) are re-ordered.

Changelog:
[General][Fixed] - **Strict TypeScript API**: Optional property types are now widened to explicitly include `| undefined` for `exactOptionalPropertyTypes` compatibility

Reviewed By: cipolleschi

Differential Revision: D113030161

fbshipit-source-id: 3ab005edab6b80b18fbb9ae7125ba56e3bd94195

Co-authored-by: Alex Hunt <huntie@meta.com>
2026-07-27 09:35:50 -04:00
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