Move AssetRegistry implementation into main package, expose as public API (#57369)

[huntie]

Summary:

Problem

The separate react-native/assets-registry package includes a longstanding ecosystem footgun.

registry.js holds asset state in a module-scoped variable, which makes the package a stateful singleton: exactly one instance must exist per JS runtime, or registration and lookup diverge.

We provide no guarantee that this singleton requirement holds:

• The install layout — how the package manager dedupes packages in node_modules — decides how many copies exist, and react-native's exact-version pin means third-party ranges never dedupe against it.

Effects:

• Consumers silently break: expo-asset and expo-image can land on a second copy: assets register in one, resolve as undefined from the other. Expo neutralizes this with a shim in expo/cli that redirects every registry import to a single virtual module — bare React Native + Metro has no such protection.
• This blocks 1.0: The ecosystem can't move from exact-version lockstep to semver ranges until stateful packages like the asset registry are safe to duplicate. Today, relaxing the pin would turn a latent footgun into a common one.

To solve this, move towards (but not quite yet) deleting react-native/assets-registry, in favour of a replacement AssetRegistry API offered directly by react-native.

Key changes

NOTE: Reviewer note: Browsing file changes on GitHub may be more focused — https://github.com/react/react-native/pull/57369/changes

NOTE: Squash of #57233 (D108750302) and #57232 (D108750303)

'react-native':

• Add new AssetRegistry API, along with the PackagerAsset and AssetDestPathResolver root type exports in react-native.
• Add a new 'react-native/asset-registry' secondary entry point — intended for Metro's transformer.assetRegistryPath config contract.

react-native/assets-registry:

• Update to source from this relocated implementation — fixing the duplicate install layout bug (where apps/frameworks enforce a single copy of react-native).

Impact

• ✅ Fixed: Imports from either react-native or react-native/assets-registry in RN 0.87+ will be durable to duplicate package installs — Expo can remove their virtual module shim.
• ✅ Fixed: Deep import 'react-native/Libraries/Image/AssetRegistry' dependency removed (migrated in react-native/metro-config).

Changelog:

• [General][Fixed] - assets-registry: react-native/assets-registry now shares state across duplicate installs, sourcing from a relocated implementation in the react-native package
• [General][Added] - Add AssetRegistry API (replaces react-native/assets-registry/registry)
• [General][Breaking] - react-native/Libraries/Image/AssetRegistry is removed. Please use the AssetRegistry API (apps/library code) and/or the react-native/asset-registry entrypoint (Metro/build configs).

Differential Revision: D109019622

[meta-codesync]

@huntie has exported this pull request. If you are a Meta employee, you can view the originating Diff in D109019622.

[github-actions]

Warning

JavaScript API change detected

This PR commits an update to ReactNativeApi.d.ts, indicating a change to React Native's public JavaScript API.

• Please include a clear changelog message.
• This change will be subject to additional review.

This change was flagged as: POTENTIALLY_NON_BREAKING

[huntie]

✅ Key change 1: Singleton module is located in the typically deduplicated react-native package (both conventionally in the ecosystem and specifically requested in this case by Expo).

[huntie]

✅ Key change 2: Deep Libraries/ import removed, and replaced with our new formal API entry point.