[metro-cache] metro-cache preview

[zhongwuzw]

Description

Introduces @module-federation/metro-cache, a new React Native native module that provides persistent on-disk caching for federated remote bundles. This eliminates redundant network downloads on app cold starts by caching bundles locally and validating them against manifest hashes (SHA-256).

What's new

@module-federation/metro-cache (new package)

• Native module with iOS (Objective-C++) and Android (Kotlin) implementations
• NativeMFECache API: downloadFile, evaluateJavaScript, deleteFile, getFileSize, getDocumentDirectory
• CacheManager: disk-backed cache index with LRU eviction, host build hash invalidation, and disk manifest persistence
• Configurable maxCacheSizeBytes, maxAgeMs, minCacheSizeBytes
• CocoaPods podspec and Android Gradle build configuration
• React Native autolinking via react-native.config.js

@module-federation/metro (metro-core) changes

• asyncRequire.ts: intercepts bundle loads with a cache layer — checks manifest hash → cache hit (eval from file) / cache miss (download + verify SHA-256 + persist) / fallback to network on mismatch
• Inflight deduplication for concurrent loads of the same bundle
• cache-interface.ts: ICacheManager / ICacheNative interfaces for loose coupling between metro-core and metro-cache (graceful degradation when metro-cache is not installed)
• metroCorePlugin.ts: afterResolve hook extracts bundle hashes from manifest (metaData.buildInfo.hash, exposes[].hash, shared[].hash) into a global __MFE_BUNDLE_HASHES__ map consumed by the cache layer
• bundle-remote/index.ts: hash computation during production bundle builds

Cache flow

bundle request → check MFE_BUNDLE_HASHES for expected hash
├─ no hash → fallback to loadBundleAsync (no cache)
└─ has hash → check CacheManager
├─ cache HIT + hash match → eval from local file
└─ cache MISS or hash mismatch → downloadFile → verify SHA-256
├─ match → persist to cache + eval from file
└─ mismatch → delete file + fallback to loadBundleAsync

Related Issue

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have added tests to cover my changes.
• All new and existing tests passed.
• I have updated the documentation.

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