Dev Dependecies in production build?

[func0der]

Hello,

I found this line on the hunt of a prod build bloatware:

react-native/packages/react-native/package.json

Line 173 in a5fc307

"babel-jest": "^29.7.0",

Shouldn't this be a devDependency? Is this a bug or can somebody explain this?

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[mensonones]

This is likely because babel-jest is required by React Native's jest-preset.js. I suspect it's listed in dependencies to make the Jest setup work out-of-the-box for everyone, but we'll have to wait for official word from the team to be sure.

If that is indeed the reason, it shouldn't cause any bloat in the final production app (APK/IPA). Metro only bundles code that is actually imported and used by the app logic, so a testing tool like babel-jest shouldn't affect the final bundle size.

It would be great to hear from the maintainers if this is the intended behavior or if moving it to peerDependencies is something that could be considered for a leaner install!

[func0der]

This is likely because babel-jest is required by React Native's jest-preset.js. I suspect it's listed in dependencies to make the Jest setup work out-of-the-box for everyone, but we'll have to wait for official word from the team to be sure.

Interesting take. I figured that everyone is creating react app with npx create-react-app my-app which can require whatever it needs in the respective devDependencies of that project then.

If that is indeed the reason, it shouldn't cause any bloat in the final production app (APK/IPA). Metro only bundles code that is actually imported and used by the app logic, so a testing tool like babel-jest shouldn't affect the final bundle size.

Is Metro even used with next.js applications or at what point is it coming into play?
I am not deep into the react universe. sorry if that is an obvious answer to this.

[mensonones]

This is likely because babel-jest is required by React Native's jest-preset.js. I suspect it's listed in dependencies to make the Jest setup work out-of-the-box for everyone, but we'll have to wait for official word from the team to be sure.

Interesting take. I figured that everyone is creating react app with npx create-react-app my-app which can require whatever it needs in the respective devDependencies of that project then.

If that is indeed the reason, it shouldn't cause any bloat in the final production app (APK/IPA). Metro only bundles code that is actually imported and used by the app logic, so a testing tool like babel-jest shouldn't affect the final bundle size.

Is Metro even used with next.js applications or at what point is it coming into play?
I am not deep into the react universe. sorry if that is an obvious answer to this.

Just to clarify a few points:

Metro is the bundler used by React Native for mobile apps. Next.js does not use Metro; for web, Next uses its own build system (webpack/next), so Metro is not part of the Next.js workflow.