Rob Hogan

This commit introduces an **experimental configuration option**, `unstable_preserveAsync`, to the **React Native Babel preset**. This **new capability** allows developers to **conditionally disable Babel's async/await and async generator function transformations**, specifically `babel/plugin-transform-async-to-generator` and `babel/plugin-transform-async-generator-functions`. The primary purpose of this **feature addition** is to facilitate **experimentation with native async/await support in Static Hermes**, potentially leading to performance improvements or reduced bundle sizes. The change affects the **Babel preset's core configuration** in `packages/react-native-babel-preset/src/configs/main.js` and includes new test cases to ensure correct behavior.

This commit **enhances the Flow type definitions** for **Node.js streams** by adding several previously missing state properties to **`stream$Readable`** and **`stream$Writable`**. Specifically, properties like `closed`, `destroyed`, `errored`, and various `readable` and `writable` state flags are now included, ensuring more accurate type checking for stream interactions. This **type definition update** is crucial for tools like **Metro**, allowing it to correctly detect client disconnects for HTTP response streams and improving the robustness of stream handling within the ecosystem.

This commit introduces a **new feature** by adding an optional `global.__BUNDLE_LOADER_REPORTER__` hook to the `loadBundleFromServer` function within `packages/react-native/Libraries/Core/Devtools/loadBundleFromServer.js`. This **enhancement** provides an **OSS-safe abstraction** for **reporting dev-mode bundle load timing and failure events** from Metro. It allows external systems to track `onStart`, `onSuccess`, and `onError` events during bundle loading, significantly improving **observability and diagnostics** for developers. The hook is designed to be a complete no-op if no reporter is installed, ensuring no overhead for projects not utilizing this **developer tooling** capability.

This commit introduces an **experimental configuration option**, `unstable_preserveClassPrivate`, to the **React Native Babel preset** (`packages/react-native-babel-preset`). This **new capability** allows developers to **conditionally disable Babel's transformation of private class fields and methods**, specifically by preventing the `babel/plugin-transform-private-methods` and `babel/plugin-transform-private-property-in-object` plugins from running. The primary purpose is to facilitate **experimentation with native private class support** within environments like **Static Hermes**, enabling the runtime to handle these features natively rather than relying on Babel's transpilation. This **feature addition** includes new snapshot tests to verify the option's behavior.

Update Metro to 0.84.2 (#55854)

This commit **refactors** the **React Native Babel transformer** to improve how Babel environments are managed. It now leverages Babel's `envName` configuration option to hint the default value of `dev`, rather than directly mutating `process.env.BABEL_ENV`. This **maintenance** change **removes potential side-effects** from environment variable manipulation, making the build process more predictable and aligning with Babel's recommended `env()` API usage. The `buildBabelConfig` and `transform` functions within `packages/react-native-babel-transformer/src/index.js` are primarily affected by this update.

This commit **fixes** an **unintended override** in the **React Native Babel preset** (`react-native-babel-preset`), which previously forced the `dev` option to `true` under certain development environment conditions, even when `dev: false` was explicitly provided. The change **removes the obsolete `withDevTools` option check** that caused this behavior. Now, the preset **infers the `dev` option using Babel's `env()` API** when it's not explicitly set, ensuring that user-defined `dev` configurations are always respected. This **refactoring** improves the predictability of build outputs and aligns the preset with standard Babel practices, with no observable change for consumers who previously worked around the issue.

Update Metro to 0.84.0 (#55672)

This commit provides a **bug fix** for the **React Native Babel transformer** (`packages/react-native-babel-transformer`), addressing an issue where `process.env.BABEL_ENV` was inadvertently modified as a side-effect during transformation. Previously, the `transform` function would incorrectly leave `process.env.BABEL_ENV` set to `'development'` or the string `'undefined'`, even if it was initially unset, leading to **non-deterministic behavior** in environments like **Metro** and **Jest**. The fix correctly restores `process.env.BABEL_ENV` by deleting it if its original value was `null` or `undefined`, preventing permanent alteration. This ensures **consistent Babel preset configuration** and more reliable test execution across the development ecosystem.

This commit performs a **dependency update**, bumping several **Babel packages** to their latest minor versions, including `code-frame`, `generator`, `parser`, `template`, `traverse`, and `types`. This **maintenance** work primarily aims to update `babel/traverse` and its dependency closure, ensuring the project's **Babel tooling infrastructure** benefits from recent improvements and bug fixes. As part of this update, **Flow type definitions** for `babel-types` are refined to correctly include an `attributes` parameter for `ExportAllDeclaration`, `ExportNamedDeclaration`, and `ImportDeclaration` nodes. This enhances the project's compatibility with modern JavaScript syntax features and improves the accuracy of its type definitions.

This commit introduces **snapshot tests** within the `react-native-babel-preset` package to validate the Babel transform output. These **new tests** cover various configurations, including `hermes-stable` and `hermes-canary`, alongside options like dev/prod modes and ESM output. Utilizing a comprehensive "kitchen-sink" fixture, this **maintenance improvement** helps **prevent regressions** and catch unintended changes in the preset's transformation logic. This ensures the `react-native-babel-preset` consistently produces expected output, enhancing the **stability** of the React Native build process.

This commit introduces a **refactoring** to the **Flow type definitions** for **yargs** by renaming `ModuleObject` to `CommandModule` in `flow-typed/npm/yargs_v17.x.x.js`. This change ensures **TypeScript consistency** by aligning the Flow type name with the existing `types/yargs` definition for modules exporting Yargs command definitions. The pragmatic rename simplifies future **Flow to TypeScript translation** efforts, as these types will no longer require special handling during conversion. This update primarily affects the **type system** and **developer experience** for projects transitioning between Flow and TypeScript.

This commit introduces **enhanced Flow type definitions** for Node.js `createServer` APIs, providing a **new capability** for improved type safety. It **upgrades the type clarity** for options in the `net`, `tls`, `http`, and `https` modules from generic `Object` to detailed specifications aligned with Node.js 24. This **type improvement** also includes exporting the `Server` type within the `ws` module's Flow definitions, ensuring more robust static analysis and a better developer experience when configuring servers.

This commit **enhances and corrects the `AbortSignal` API** within **React Native's Flow type definitions**. It **updates the type signatures** for `AbortSignal.abort` and `AbortSignal.timeout` to correctly reflect their static nature, aligning with web standards. Additionally, this change **introduces the `AbortSignal.any` static method**, enabling developers to create a composite signal that aborts when any of its constituent signals abort. This ensures **accurate type checking** for `AbortSignal`'s static methods and provides a **new capability for managing cancellation logic** in applications.

This commit **adds Flow type definitions** for the **experimental Node.js `node:sqlite` module**, which provides synchronous SQLite database operations. It introduces comprehensive types for the `DatabaseSync`, `StatementSync`, and `Session` classes, enabling **type-safe usage** of this built-in database interface. This **new capability** enhances developer experience by providing compile-time type checking for applications utilizing Node.js v22.5.0 and later, ensuring better code quality and maintainability when interacting with embedded SQLite databases.

This commit **updates the Flow type definitions** for the **Node.js `v8` module** to align with Node.js v24. It introduces type definitions for several new APIs, including **heap snapshot automation**, **garbage collection profiling**, **object instance querying**, and **C++ heap statistics**, which were added in Node.js versions 18 through 22. Furthermore, it refines existing type signatures for heap statistics and snapshot functions, ensuring **comprehensive and accurate type coverage** for modern Node.js environments. This **maintenance** work improves developer experience and prevents type errors when interacting with the `v8` module.

This commit performs a **refactoring** within the **`dev-middleware` package** to replace the deprecated Node.js `url.parse` function with the modern `new URL()` and `URLSearchParams` APIs. Specifically, the `inspector-proxy` and `openDebuggerMiddleware` components, along with their tests, are updated to use the contemporary URL parsing methods. This **maintenance** effort addresses a **deprecation warning** emitted by Node.js 24+, thereby **eliminating runtime noise** for developers working directly with the monorepo source, without affecting React Native end-users.

This commit performs **maintenance** by **updating Flow type definitions** for **Babel packages** (`@babel/traverse` and `@babel/types`) to align with the latest Babel AST changes, resolving issues with no-lockfile CI. It introduces new type declarations for constructs like `ImportAttribute`, `VoidPattern`, and `FunctionParameter`, along with their corresponding helper functions, ensuring accurate type checking for projects consuming these Babel types. Additionally, it includes a **bug fix** in `scripts/js-api/build-types/transforms/typescript/simplifyTypes/resolveTypeOperator.js` to handle null type operators gracefully. Finally, it performs a `yarn-deduplicate` operation specifically for **Metro's dependencies**, further enhancing stability. This work is crucial for maintaining **internal type compatibility** and preventing build failures.

This commit performs a significant **maintenance update** to the **Flow type definitions** for Node.js's `child_process` module, aligning them with features introduced up to Node.js v24. It introduces **new capabilities** suching as `AbortSignal` support for process cancellation and enhanced IPC options for `fork` and `spawn`, alongside **refinements** to existing method signatures and property types for `ChildProcess` instances. The update also improves **type safety** by using modern `Readonly` syntax for options and fixing nullable return types for `spawnRet`/`spawnSyncRet`. This ensures that projects leveraging these definitions can correctly utilize and benefit from the latest Node.js `child_process` APIs.

This commit introduces a **breaking change** by **dropping support for older Node.js versions**, specifically those released before `20.19.4` and the end-of-life (EOL) versions `21` and `23`. This **maintenance update** aligns the project's `package.json#engines` field with the official documentation, ensuring developers use a consistent and supported Node.js environment. The change enables the use of modern Node.js features, such as stable and unflagged `require(esm)`, by removing compatibility constraints with outdated or unsupported runtimes. Consequently, developers must upgrade their Node.js installations to `20.19.4` or newer to continue working with the project.