Package subpath './package.json' is not defined by "exports"

Environment

System:
    OS: macOS 10.15.4
    CPU: (4) x64 Intel(R) Core(TM) i7-5557U CPU @ 3.10GHz
    Memory: 94.37 MB / 16.00 GB
    Shell: 5.7.1 - /bin/zsh
  Binaries:
    Node: 14.2.0 - /usr/local/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.4 - /usr/local/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  Managers:
    CocoaPods: 1.9.1 - /usr/local/bin/pod
  SDKs:
    iOS SDK:
      Platforms: iOS 13.4, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
    Android SDK: Not Found
  IDEs:
    Android Studio: Not Found
    Xcode: 11.4.1/11E503a - /usr/bin/xcodebuild
  Languages:
    Java: 1.8.0_121 - /usr/bin/javac
    Python: 3.7.7 - /usr/local/opt/python/libexec/bin/python
  npmPackages:
    @react-native-community/cli: Not Found
    react: 16.13.1 => 16.13.1
    react-native: 0.62.2 => 0.62.2
  npmGlobalPackages:
    *react-native*: Not Found

Description

When running react-native under Node.js 14.x on a project that uses npm modules which specify the new exports field in package.json, react-native will print the following warning (in this example the uuid package is used):

warn Package uuid has been ignored because it contains invalid configuration. Reason: Package subpath './package.json' is not defined by "exports" in /PATH_TO_CURRENT_PROJECT/node_modules/uuid/package.json

The same issue has been reported in other places:

• i18next-http-backend: https://github.com/facebook/react-native/issues/28710 for (workaround: https://github.com/i18next/i18next-http-backend/commit/1d8da7909425eb33ab286cd73ee53bb48a1a3dc4#diff-b9cfc7f2cdf78a7f4b91a753d10865a2R8)
• i18next-locize-backend: https://github.com/locize/i18next-locize-backend/pull/326/files
• nanoevents: https://github.com/ai/nanoevents/issues/44
• uuid: https://github.com/uuidjs/uuid/issues/444#issuecomment-627216425

The reason is that, starting in Node.js 14.x, as soon as an npm module defines the exports field in package.json, only the files listed there are exported. If package.json is not included in that list, it’s no longer possible to do things like require.resolve('uuid/package.json');.

The problematic piece of code is: https://github.com/react-native-community/cli/blob/5819a17d148726a1185420b6df345dad6c81c81b/packages/cli/src/tools/config/resolveNodeModuleDir.ts#L11-L13

For a package like uuid which does not contain react-native specific configuration in package.json this is not a problem, but for modules that do contain such config in package.json they will be forced to add package.json to their exports field.

An alternative would be to not rely on require.resolve and instead use https://github.com/browserify/resolve

As far as I know this is how rollup.js solves this issue, see https://github.com/rollup/plugins/issues/208#issuecomment-614319271

What is the maintainers take on this? Do you think that every single module on npm that starts making use of the exports field should include package.json in the exports? Or could this be fixed in react-native?

Reproducible Demo

1. Use Node.js 14.x
2. npm i uuid@8.0.0
3. Open noderepl:

> require.resolve('uuid/package.json');
Uncaught:
Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './package.json' is not defined by "exports" in /PROJECT/node_modules/uuid/package.json
    at applyExports (internal/modules/cjs/loader.js:491:9)
    at resolveExports (internal/modules/cjs/loader.js:507:23)
    at Function.Module._findPath (internal/modules/cjs/loader.js:635:31)
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:1007:27)
    at Function.resolve (internal/modules/cjs/helpers.js:78:19)
    at repl:1:9
    at Script.runInThisContext (vm.js:131:20)
    at REPLServer.defaultEval (repl.js:436:29)
    at bound (domain.js:429:14)
    at REPLServer.runBound [as eval] (domain.js:442:12) {
  code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}

[mifi]

What’s the consequence of the warning? Does it mean that the package in question will not be included in the bundle?

[sindresorhus]

Please don’t open issues/PRs on open source projects about this. It is not expected that packages export their package.json file. This is a problem React Native needs to fix, not every single package out there.