### What happened When running an Expo app that depends on `react-phone-number-input@3.4.12` (which uses `libphonenumber-js`), Metro prints this warning: > WARN The package <MY_APP_ROOT>/node_modules/libphonenumber-js/min/metadata contains an invalid package.json configuration. Consider raising this issue with the package maintainer(s). > Reason: One or more mappings for subpaths defined in "exports" are invalid. All values must begin with "./". Falling back to file-based resolution. The app continues to work, but the warning appears on every cold start. ### Repro steps 1. `npx create-expo-app myapp` 2. `npm i react-phone-number-input@3.4.12` 3. Import anything from the package, e.g.: ```js import PhoneInput from 'react-phone-number-input' ``` 4. `npx expo start` → open the app and observe the Metro warning above. ## Environment - Expo (SDK 53+) - Metro (package exports enabled) - Platforms: iOS / Android / Web (warning is shown in Metro logs) - `react-phone-number-input`: 3.4.12 - `libphonenumber-js`: as installed via the dependency above ## Why this happens `libphonenumber-js` includes a nested package at `min/metadata` whose `package.json` contains `exports` mappings that point **outside** that subpackage via `../../...`. Per Node’s package exports rules, **export targets must be relative paths that start with `"./"`** (and must not traverse up with `..`). Metro enforces this, warns, and then falls back to legacy file-based resolution so the app still runs. An example of the problematic mapping in `min/metadata/package.json`: ```json { "exports": { ".": { "types": "../../metadata.min.json.d.ts", "import": "../../metadata.min.json.js", "require": "../../metadata.min.json" } } } ``` Because the subpackage root is min/metadata/, those ../../ targets violate the "./" requirement. ## Suggested fixes Any of the following would remove the warning and make the package spec-compliant: * **Option A (preferred):** Expose metadata via the root package’s exports without a nested subpackage: ```json { "name": "libphonenumber-js", "exports": { "./min/metadata": { "types": "./metadata.min.json.d.ts", "import": "./metadata.min.json.js", "require": "./metadata.min.json" } // Optionally the same for: ./max/metadata, ./mobile/metadata } } ``` * **Option B:** Keep the nested min/metadata package, but make its files local and its exports targets start with "./" (would require duplicating or moving the files into that folder) ```json { "name": "libphonenumber-js/min/metadata", "exports": { ".": { "types": "./metadata.min.json.d.ts", "import": "./metadata.min.json.js", "require": "./metadata.min.json" } } } ``` ### References * Node.js docs on "exports" target formats (targets must start with ./): https://nodejs.org/api/packages.html#exports * Metro package exports background (warning & fallback behavior): https://metrobundler.dev/docs/configuration/#unstable_enablepackageexports-experimental Thanks for taking a look! I’m happy to test a prerelease or proposed fix.